Patchwork net/core: BUG in copy_net_ns()

login
register
mail settings
Submitter zzoru
Date Jan. 11, 2019, 6:07 p.m.
Message ID <bc63c776-99f9-ca6e-0e81-f91b1448932b@gmail.com>
Download mbox | patch
Permalink /patch/697971/
State New
Headers show

Comments

zzoru - Jan. 11, 2019, 6:07 p.m.
net/core: BUG in copy_net_ns() (net_namespace.c)

Hello,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit 1bdbe227492075d058e37cb3d400e6468d0095b5

Syzkaller hit 'WARNING in __alloc_pages_slowpath' bug.

syz-executor561 (17453) used greatest stack depth: 25056 bytes left
WARNING: CPU: 0 PID: 692 at mm/page_alloc.c:4415
__alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4386
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 692 Comm: kswapd0 Not tainted 5.0.0-rc1+ #4
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xca/0x13e lib/dump_stack.c:113
 panic+0x278/0x5bf kernel/panic.c:214
 __warn.cold.10+0x20/0x45 kernel/panic.c:571
 report_bug+0x246/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x123/0x1e0 arch/x86/kernel/traps.c:271
 do_invalid_op+0x31/0x40 arch/x86/kernel/traps.c:290
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:__alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4415
Code: 8b 84 24 a8 00 00 00 e9 ea f1 ff ff 85 d2 0f 85 0b 01 00 00 48 c7
c7 c0 5e 55 84 e8 79 f8 23 02 e9 86 f9 ff ff 44 8b 74 24 0c <0f> 0b 48
b8 00 00 00 00 00 fc ff df 48 8b 54 24 18 48 c1 ea 03 80
RSP: 0018:ffff8880683fedb8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffff1100d07fda4
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807ffdd528
RBP: dffffc0000000000 R08: 0000000000000000 R09: 000000000000067a
R10: 0000000000000000 R11: ffff88807ffdc487 R12: 0000000000000000
R13: ffff8880683ff010 R14: 0000000000415a00 R15: ffff8880683ff010
 __alloc_pages_nodemask+0x521/0x5f0 mm/page_alloc.c:4555
 __alloc_pages include/linux/gfp.h:473 [inline]
 __alloc_pages_node include/linux/gfp.h:486 [inline]
 kmem_getpages mm/slab.c:1398 [inline]
 cache_grow_begin+0x95/0x300 mm/slab.c:2666
 fallback_alloc+0x1ce/0x270 mm/slab.c:3208
 __do_cache_alloc mm/slab.c:3345 [inline]
 slab_alloc mm/slab.c:3373 [inline]
 kmem_cache_alloc+0x286/0x2f0 mm/slab.c:3541
 create_object+0x83/0x880 mm/kmemleak.c:578
 kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline]
 slab_post_alloc_hook mm/slab.h:442 [inline]
 slab_alloc mm/slab.c:3381 [inline]
 kmem_cache_alloc+0x18f/0x2f0 mm/slab.c:3541
 mempool_alloc+0x13e/0x340 mm/mempool.c:385
 bio_alloc_bioset+0x36f/0x5d0 block/bio.c:489
 bio_alloc include/linux/bio.h:393 [inline]
 submit_bh_wbc.isra.57+0x128/0x680 fs/buffer.c:3061
 __block_write_full_page+0x6e8/0xcd0 fs/buffer.c:1765
 block_write_full_page+0x202/0x250 fs/buffer.c:2955
 pageout mm/vmscan.c:865 [inline]
 shrink_page_list+0x220f/0x3800 mm/vmscan.c:1383
 shrink_inactive_list+0x3c2/0xaa0 mm/vmscan.c:1961
 shrink_list mm/vmscan.c:2273 [inline]
 shrink_node_memcg.constprop.83+0x4bf/0x10e0 mm/vmscan.c:2538
 shrink_node+0x162/0xd10 mm/vmscan.c:2753
 kswapd_shrink_node mm/vmscan.c:3516 [inline]
 balance_pgdat+0x47f/0xc00 mm/vmscan.c:3674
 kswapd+0x57c/0xde0 mm/vmscan.c:3929
 kthread+0x347/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


Syzkaller reproducer:
# {Threaded:false Collide:false Repeat:true RepeatTimes:0 Procs:8
Sandbox:none Fault:false FaultCall:-1 FaultNth:0 EnableTun:false
UseTmpDir:true EnableCgroups:false EnableNetdev:true ResetNet:false
HandleSegv:false Repro:false Trace:false}
unshare(0x40000000)


C reproducer:
// autogenerated by syzkaller (https://github.com/google/syzkaller)

#define _GNU_SOURCE

#include <arpa/inet.h>
#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <sched.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#include <linux/if_addr.h>
#include <linux/if_ether.h>
#include <linux/if_link.h>
#include <linux/if_tun.h>
#include <linux/in6.h>
#include <linux/ip.h>
#include <linux/neighbour.h>
#include <linux/net.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/tcp.h>
#include <linux/veth.h>

unsigned long long procid;

static void sleep_ms(uint64_t ms)
{
  usleep(ms * 1000);
}

static uint64_t current_time_ms(void)
{
  struct timespec ts;
  if (clock_gettime(CLOCK_MONOTONIC, &ts))
    exit(1);
  return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}

static void use_temporary_dir(void)
{
  char tmpdir_template[] = "./syzkaller.XXXXXX";
  char* tmpdir = mkdtemp(tmpdir_template);
  if (!tmpdir)
    exit(1);
  if (chmod(tmpdir, 0777))
    exit(1);
  if (chdir(tmpdir))
    exit(1);
}

static bool write_file(const char* file, const char* what, ...)
{
  char buf[1024];
  va_list args;
  va_start(args, what);
  vsnprintf(buf, sizeof(buf), what, args);
  va_end(args);
  buf[sizeof(buf) - 1] = 0;
  int len = strlen(buf);
  int fd = open(file, O_WRONLY | O_CLOEXEC);
  if (fd == -1)
    return false;
  if (write(fd, buf, len) != len) {
    int err = errno;
    close(fd);
    errno = err;
    return false;
  }
  close(fd);
  return true;
}

static struct {
  char* pos;
  int nesting;
  struct nlattr* nested[8];
  char buf[1024];
} nlmsg;

static void netlink_init(int typ, int flags, const void* data, int size)
{
  memset(&nlmsg, 0, sizeof(nlmsg));
  struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;
  hdr->nlmsg_type = typ;
  hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
  memcpy(hdr + 1, data, size);
  nlmsg.pos = (char*)(hdr + 1) + NLMSG_ALIGN(size);
}

static void netlink_attr(int typ, const void* data, int size)
{
  struct nlattr* attr = (struct nlattr*)nlmsg.pos;
  attr->nla_len = sizeof(*attr) + size;
  attr->nla_type = typ;
  memcpy(attr + 1, data, size);
  nlmsg.pos += NLMSG_ALIGN(attr->nla_len);
}

static void netlink_nest(int typ)
{
  struct nlattr* attr = (struct nlattr*)nlmsg.pos;
  attr->nla_type = typ;
  nlmsg.pos += sizeof(*attr);
  nlmsg.nested[nlmsg.nesting++] = attr;
}

static void netlink_done(void)
{
  struct nlattr* attr = nlmsg.nested[--nlmsg.nesting];
  attr->nla_len = nlmsg.pos - (char*)attr;
}

static int netlink_send(int sock)
{
  if (nlmsg.pos > nlmsg.buf + sizeof(nlmsg.buf) || nlmsg.nesting)
    exit(1);
  struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;
  hdr->nlmsg_len = nlmsg.pos - nlmsg.buf;
  struct sockaddr_nl addr;
  memset(&addr, 0, sizeof(addr));
  addr.nl_family = AF_NETLINK;
  unsigned n = sendto(sock, nlmsg.buf, hdr->nlmsg_len, 0,
                      (struct sockaddr*)&addr, sizeof(addr));
  if (n != hdr->nlmsg_len)
    exit(1);
  n = recv(sock, nlmsg.buf, sizeof(nlmsg.buf), 0);
  if (n < sizeof(struct nlmsghdr) + sizeof(struct nlmsgerr))
    exit(1);
  if (hdr->nlmsg_type != NLMSG_ERROR)
    exit(1);
  return -((struct nlmsgerr*)(hdr + 1))->error;
}

static void netlink_add_device_impl(const char* type, const char* name)
{
  struct ifinfomsg hdr;
  memset(&hdr, 0, sizeof(hdr));
  netlink_init(RTM_NEWLINK, NLM_F_EXCL | NLM_F_CREATE, &hdr, sizeof(hdr));
  if (name)
    netlink_attr(IFLA_IFNAME, name, strlen(name));
  netlink_nest(IFLA_LINKINFO);
  netlink_attr(IFLA_INFO_KIND, type, strlen(type));
}

static void netlink_add_device(int sock, const char* type, const char* name)
{
  netlink_add_device_impl(type, name);
  netlink_done();
  int err = netlink_send(sock);
  (void)err;
}

static void netlink_add_veth(int sock, const char* name, const char* peer)
{
  netlink_add_device_impl("veth", name);
  netlink_nest(IFLA_INFO_DATA);
  netlink_nest(VETH_INFO_PEER);
  nlmsg.pos += sizeof(struct ifinfomsg);
  netlink_attr(IFLA_IFNAME, peer, strlen(peer));
  netlink_done();
  netlink_done();
  netlink_done();
  int err = netlink_send(sock);
  (void)err;
}

static void netlink_add_hsr(int sock, const char* name, const char* slave1,
                            const char* slave2)
{
  netlink_add_device_impl("hsr", name);
  netlink_nest(IFLA_INFO_DATA);
  int ifindex1 = if_nametoindex(slave1);
  netlink_attr(IFLA_HSR_SLAVE1, &ifindex1, sizeof(ifindex1));
  int ifindex2 = if_nametoindex(slave2);
  netlink_attr(IFLA_HSR_SLAVE2, &ifindex2, sizeof(ifindex2));
  netlink_done();
  netlink_done();
  int err = netlink_send(sock);
  (void)err;
}

static void netlink_device_change(int sock, const char* name, bool up,
                                  const char* master, const void* mac,
                                  int macsize)
{
  struct ifinfomsg hdr;
  memset(&hdr, 0, sizeof(hdr));
  if (up)
    hdr.ifi_flags = hdr.ifi_change = IFF_UP;
  netlink_init(RTM_NEWLINK, 0, &hdr, sizeof(hdr));
  netlink_attr(IFLA_IFNAME, name, strlen(name));
  if (master) {
    int ifindex = if_nametoindex(master);
    netlink_attr(IFLA_MASTER, &ifindex, sizeof(ifindex));
  }
  if (macsize)
    netlink_attr(IFLA_ADDRESS, mac, macsize);
  int err = netlink_send(sock);
  (void)err;
}

static int netlink_add_addr(int sock, const char* dev, const void* addr,
                            int addrsize)
{
  struct ifaddrmsg hdr;
  memset(&hdr, 0, sizeof(hdr));
  hdr.ifa_family = addrsize == 4 ? AF_INET : AF_INET6;
  hdr.ifa_prefixlen = addrsize == 4 ? 24 : 120;
  hdr.ifa_scope = RT_SCOPE_UNIVERSE;
  hdr.ifa_index = if_nametoindex(dev);
  netlink_init(RTM_NEWADDR, NLM_F_CREATE | NLM_F_REPLACE, &hdr,
sizeof(hdr));
  netlink_attr(IFA_LOCAL, addr, addrsize);
  netlink_attr(IFA_ADDRESS, addr, addrsize);
  return netlink_send(sock);
}

static void netlink_add_addr4(int sock, const char* dev, const char* addr)
{
  struct in_addr in_addr;
  inet_pton(AF_INET, addr, &in_addr);
  int err = netlink_add_addr(sock, dev, &in_addr, sizeof(in_addr));
  (void)err;
}

static void netlink_add_addr6(int sock, const char* dev, const char* addr)
{
  struct in6_addr in6_addr;
  inet_pton(AF_INET6, addr, &in6_addr);
  int err = netlink_add_addr(sock, dev, &in6_addr, sizeof(in6_addr));
  (void)err;
}

#define DEV_IPV4 "172.20.20.%d"
#define DEV_IPV6 "fe80::%02hx"
#define DEV_MAC 0x00aaaaaaaaaa
static void initialize_netdevices(void)
{
  char netdevsim[16];
  sprintf(netdevsim, "netdevsim%d", (int)procid);
  struct {
    const char* type;
    const char* dev;
  } devtypes[] = {
      {"ip6gretap", "ip6gretap0"}, {"bridge", "bridge0"},
      {"vcan", "vcan0"},           {"bond", "bond0"},
      {"team", "team0"},           {"dummy", "dummy0"},
      {"nlmon", "nlmon0"},         {"caif", "caif0"},
      {"batadv", "batadv0"},       {"vxcan", "vxcan1"},
      {"netdevsim", netdevsim},    {"veth", 0},
  };
  const char* devmasters[] = {"bridge", "bond", "team"};
  struct {
    const char* name;
    int macsize;
    bool noipv6;
  } devices[] = {
      {"lo", ETH_ALEN},
      {"sit0", 0},
      {"bridge0", ETH_ALEN},
      {"vcan0", 0, true},
      {"tunl0", 0},
      {"gre0", 0},
      {"gretap0", ETH_ALEN},
      {"ip_vti0", 0},
      {"ip6_vti0", 0},
      {"ip6tnl0", 0},
      {"ip6gre0", 0},
      {"ip6gretap0", ETH_ALEN},
      {"erspan0", ETH_ALEN},
      {"bond0", ETH_ALEN},
      {"veth0", ETH_ALEN},
      {"veth1", ETH_ALEN},
      {"team0", ETH_ALEN},
      {"veth0_to_bridge", ETH_ALEN},
      {"veth1_to_bridge", ETH_ALEN},
      {"veth0_to_bond", ETH_ALEN},
      {"veth1_to_bond", ETH_ALEN},
      {"veth0_to_team", ETH_ALEN},
      {"veth1_to_team", ETH_ALEN},
      {"veth0_to_hsr", ETH_ALEN},
      {"veth1_to_hsr", ETH_ALEN},
      {"hsr0", 0},
      {"dummy0", ETH_ALEN},
      {"nlmon0", 0},
      {"vxcan1", 0, true},
      {"caif0", ETH_ALEN},
      {"batadv0", ETH_ALEN},
      {netdevsim, ETH_ALEN},
  };
  int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
  if (sock == -1)
    exit(1);
  unsigned i;
  for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++)
    netlink_add_device(sock, devtypes[i].type, devtypes[i].dev);
  for (i = 0; i < sizeof(devmasters) / (sizeof(devmasters[0])); i++) {
    char master[32], slave0[32], veth0[32], slave1[32], veth1[32];
    sprintf(slave0, "%s_slave_0", devmasters[i]);
    sprintf(veth0, "veth0_to_%s", devmasters[i]);
    netlink_add_veth(sock, slave0, veth0);
    sprintf(slave1, "%s_slave_1", devmasters[i]);
    sprintf(veth1, "veth1_to_%s", devmasters[i]);
    netlink_add_veth(sock, slave1, veth1);
    sprintf(master, "%s0", devmasters[i]);
    netlink_device_change(sock, slave0, false, master, 0, 0);
    netlink_device_change(sock, slave1, false, master, 0, 0);
  }
  netlink_device_change(sock, "bridge_slave_0", true, 0, 0, 0);
  netlink_device_change(sock, "bridge_slave_1", true, 0, 0, 0);
  netlink_add_veth(sock, "hsr_slave_0", "veth0_to_hsr");
  netlink_add_veth(sock, "hsr_slave_1", "veth1_to_hsr");
  netlink_add_hsr(sock, "hsr0", "hsr_slave_0", "hsr_slave_1");
  netlink_device_change(sock, "hsr_slave_0", true, 0, 0, 0);
  netlink_device_change(sock, "hsr_slave_1", true, 0, 0, 0);
  for (i = 0; i < sizeof(devices) / (sizeof(devices[0])); i++) {
    char addr[32];
    sprintf(addr, DEV_IPV4, i + 10);
    netlink_add_addr4(sock, devices[i].name, addr);
    if (!devices[i].noipv6) {
      sprintf(addr, DEV_IPV6, i + 10);
      netlink_add_addr6(sock, devices[i].name, addr);
    }
    uint64_t macaddr = DEV_MAC + ((i + 10ull) << 40);
    netlink_device_change(sock, devices[i].name, true, 0, &macaddr,
                          devices[i].macsize);
  }
  close(sock);
}
static void initialize_netdevices_init(void)
{
  int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
  if (sock == -1)
    exit(1);
  struct {
    const char* type;
    int macsize;
    bool noipv6;
    bool noup;
  } devtypes[] = {
      {"nr", 7, true}, {"rose", 5, true, true},
  };
  unsigned i;
  for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++) {
    char dev[32], addr[32];
    sprintf(dev, "%s%d", devtypes[i].type, (int)procid);
    sprintf(addr, "172.30.%d.%d", i, (int)procid + 1);
    netlink_add_addr4(sock, dev, addr);
    if (!devtypes[i].noipv6) {
      sprintf(addr, "fe88::%02hx:%02hx", i, (int)procid + 1);
      netlink_add_addr6(sock, dev, addr);
    }
    int macsize = devtypes[i].macsize;
    uint64_t macaddr = 0xbbbbbb +
                       ((unsigned long long)i << (8 * (macsize - 2))) +
                       (procid << (8 * (macsize - 1)));
    netlink_device_change(sock, dev, !devtypes[i].noup, 0, &macaddr,
macsize);
  }
  close(sock);
}

static void setup_common()
{
  if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
  }
}

static void loop();

static void sandbox_common()
{
  prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
  setpgrp();
  setsid();
  struct rlimit rlim;
  rlim.rlim_cur = rlim.rlim_max = 200 << 20;
  setrlimit(RLIMIT_AS, &rlim);
  rlim.rlim_cur = rlim.rlim_max = 32 << 20;
  setrlimit(RLIMIT_MEMLOCK, &rlim);
  rlim.rlim_cur = rlim.rlim_max = 136 << 20;
  setrlimit(RLIMIT_FSIZE, &rlim);
  rlim.rlim_cur = rlim.rlim_max = 1 << 20;
  setrlimit(RLIMIT_STACK, &rlim);
  rlim.rlim_cur = rlim.rlim_max = 0;
  setrlimit(RLIMIT_CORE, &rlim);
  rlim.rlim_cur = rlim.rlim_max = 256;
  setrlimit(RLIMIT_NOFILE, &rlim);
  if (unshare(CLONE_NEWNS)) {
  }
  if (unshare(CLONE_NEWIPC)) {
  }
  if (unshare(0x02000000)) {
  }
  if (unshare(CLONE_NEWUTS)) {
  }
  if (unshare(CLONE_SYSVSEM)) {
  }
  typedef struct {
    const char* name;
    const char* value;
  } sysctl_t;
  static const sysctl_t sysctls[] = {
      {"/proc/sys/kernel/shmmax", "16777216"},
      {"/proc/sys/kernel/shmall", "536870912"},
      {"/proc/sys/kernel/shmmni", "1024"},
      {"/proc/sys/kernel/msgmax", "8192"},
      {"/proc/sys/kernel/msgmni", "1024"},
      {"/proc/sys/kernel/msgmnb", "1024"},
      {"/proc/sys/kernel/sem", "1024 1048576 500 1024"},
  };
  unsigned i;
  for (i = 0; i < sizeof(sysctls) / sizeof(sysctls[0]); i++)
    write_file(sysctls[i].name, sysctls[i].value);
}

int wait_for_loop(int pid)
{
  if (pid < 0)
    exit(1);
  int status = 0;
  while (waitpid(-1, &status, __WALL) != pid) {
  }
  return WEXITSTATUS(status);
}

static int do_sandbox_none(void)
{
  if (unshare(CLONE_NEWPID)) {
  }
  int pid = fork();
  if (pid != 0)
    return wait_for_loop(pid);
  setup_common();
  sandbox_common();
  initialize_netdevices_init();
  if (unshare(CLONE_NEWNET)) {
  }
  initialize_netdevices();
  loop();
  exit(1);
}

#define FS_IOC_SETFLAGS _IOW('f', 2, long)
static void remove_dir(const char* dir)
{
  DIR* dp;
  struct dirent* ep;
  int iter = 0;
retry:
  while (umount2(dir, MNT_DETACH) == 0) {
  }
  dp = opendir(dir);
  if (dp == NULL) {
    if (errno == EMFILE) {
      exit(1);
    }
    exit(1);
  }
  while ((ep = readdir(dp))) {
    if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0)
      continue;
    char filename[FILENAME_MAX];
    snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name);
    while (umount2(filename, MNT_DETACH) == 0) {
    }
    struct stat st;
    if (lstat(filename, &st))
      exit(1);
    if (S_ISDIR(st.st_mode)) {
      remove_dir(filename);
      continue;
    }
    int i;
    for (i = 0;; i++) {
      if (unlink(filename) == 0)
        break;
      if (errno == EPERM) {
        int fd = open(filename, O_RDONLY);
        if (fd != -1) {
          long flags = 0;
          if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
            close(fd);
          continue;
        }
      }
      if (errno == EROFS) {
        break;
      }
      if (errno != EBUSY || i > 100)
        exit(1);
      if (umount2(filename, MNT_DETACH))
        exit(1);
    }
  }
  closedir(dp);
  int i;
  for (i = 0;; i++) {
    if (rmdir(dir) == 0)
      break;
    if (i < 100) {
      if (errno == EPERM) {
        int fd = open(dir, O_RDONLY);
        if (fd != -1) {
          long flags = 0;
          if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
            close(fd);
          continue;
        }
      }
      if (errno == EROFS) {
        break;
      }
      if (errno == EBUSY) {
        if (umount2(dir, MNT_DETACH))
          exit(1);
        continue;
      }
      if (errno == ENOTEMPTY) {
        if (iter < 100) {
          iter++;
          goto retry;
        }
      }
    }
    exit(1);
  }
}

static void kill_and_wait(int pid, int* status)
{
  kill(-pid, SIGKILL);
  kill(pid, SIGKILL);
  int i;
  for (i = 0; i < 100; i++) {
    if (waitpid(-1, status, WNOHANG | __WALL) == pid)
      return;
    usleep(1000);
  }
  DIR* dir = opendir("/sys/fs/fuse/connections");
  if (dir) {
    for (;;) {
      struct dirent* ent = readdir(dir);
      if (!ent)
        break;
      if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
        continue;
      char abort[300];
      snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
               ent->d_name);
      int fd = open(abort, O_WRONLY);
      if (fd == -1) {
        continue;
      }
      if (write(fd, abort, 1) < 0) {
      }
      close(fd);
    }
    closedir(dir);
  } else {
  }
  while (waitpid(-1, status, __WALL) != pid) {
  }
}

#define SYZ_HAVE_SETUP_TEST 1
static void setup_test()
{
  prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
  setpgrp();
}

#define SYZ_HAVE_RESET_TEST 1
static void reset_test()
{
  int fd;
  for (fd = 3; fd < 30; fd++)
    close(fd);
}

static void execute_one(void);

#define WAIT_FLAGS __WALL

static void loop(void)
{
  int iter;
  for (iter = 0;; iter++) {
    char cwdbuf[32];
    sprintf(cwdbuf, "./%d", iter);
    if (mkdir(cwdbuf, 0777))
      exit(1);
    int pid = fork();
    if (pid < 0)
      exit(1);
    if (pid == 0) {
      if (chdir(cwdbuf))
        exit(1);
      setup_test();
      execute_one();
      reset_test();
      exit(0);
    }
    int status = 0;
    uint64_t start = current_time_ms();
    for (;;) {
      if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
        break;
      sleep_ms(1);
      if (current_time_ms() - start < 5 * 1000)
        continue;
      kill_and_wait(pid, &status);
      break;
    }
    remove_dir(cwdbuf);
  }
}

void execute_one(void)
{
  syscall(__NR_unshare, 0x40000000);
}
int main(void)
{
  syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
  for (procid = 0; procid < 8; procid++) {
    if (fork() == 0) {
      use_temporary_dir();
      do_sandbox_none();
    }
  }
  sleep(1000000);
  return 0;
}


I reviewed kernel code and found a bug that
net_drop_ns func doesn't call net_free func when refcount_dec_and_test's
return value is zero.
or
when rv = down_read_killable(&pernet_ops_rwsem) < 0, it doesn't need to
call refcount_dec_and_test.
https://github.com/torvalds/linux/commit/5ba049a5cc8e24a1643df75bbf65b4efa070fa74#diff-9312644e2968a45510bacdd2b2872ad2
(I can't reproduce this bug on v4.15 , and
1bdbe227492075d058e37cb3d400e6468d0095b5 with my patch. Because of the
previous version of kernel doesn't have this bug.)
This bug can lead to memory leak or DOS.

I made a patch for this bug. (just revert to a before commit)


and, sorry for my encrypted mails.
Eric W. Biederman - Jan. 11, 2019, 8:33 p.m.
zzoru <zzoru007@gmail.com> writes:

> net/core: BUG in copy_net_ns() (net_namespace.c)

I don't understand this failure report at all.

I don't see the connection to copy_net_ns().  And I don't see how the
suggested patch short of covering up a memory stomp could possibly make
a difference.

What am I missing?


> Hello,
>
> I've got the following error report while fuzzing the kernel with syzkaller.
>
> On commit 1bdbe227492075d058e37cb3d400e6468d0095b5
>
> Syzkaller hit 'WARNING in __alloc_pages_slowpath' bug.
>
> syz-executor561 (17453) used greatest stack depth: 25056 bytes left
> WARNING: CPU: 0 PID: 692 at mm/page_alloc.c:4415
> __alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4386
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 0 PID: 692 Comm: kswapd0 Not tainted 5.0.0-rc1+ #4
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> Ubuntu-1.8.2-1ubuntu1 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0xca/0x13e lib/dump_stack.c:113
>  panic+0x278/0x5bf kernel/panic.c:214
>  __warn.cold.10+0x20/0x45 kernel/panic.c:571
>  report_bug+0x246/0x2d0 lib/bug.c:186
>  fixup_bug arch/x86/kernel/traps.c:178 [inline]
>  do_error_trap+0x123/0x1e0 arch/x86/kernel/traps.c:271
>  do_invalid_op+0x31/0x40 arch/x86/kernel/traps.c:290
>  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
> RIP: 0010:__alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4415
> Code: 8b 84 24 a8 00 00 00 e9 ea f1 ff ff 85 d2 0f 85 0b 01 00 00 48 c7
> c7 c0 5e 55 84 e8 79 f8 23 02 e9 86 f9 ff ff 44 8b 74 24 0c <0f> 0b 48
> b8 00 00 00 00 00 fc ff df 48 8b 54 24 18 48 c1 ea 03 80
> RSP: 0018:ffff8880683fedb8 EFLAGS: 00010046
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffff1100d07fda4
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807ffdd528
> RBP: dffffc0000000000 R08: 0000000000000000 R09: 000000000000067a
> R10: 0000000000000000 R11: ffff88807ffdc487 R12: 0000000000000000
> R13: ffff8880683ff010 R14: 0000000000415a00 R15: ffff8880683ff010
>  __alloc_pages_nodemask+0x521/0x5f0 mm/page_alloc.c:4555
>  __alloc_pages include/linux/gfp.h:473 [inline]
>  __alloc_pages_node include/linux/gfp.h:486 [inline]
>  kmem_getpages mm/slab.c:1398 [inline]
>  cache_grow_begin+0x95/0x300 mm/slab.c:2666
>  fallback_alloc+0x1ce/0x270 mm/slab.c:3208
>  __do_cache_alloc mm/slab.c:3345 [inline]
>  slab_alloc mm/slab.c:3373 [inline]
>  kmem_cache_alloc+0x286/0x2f0 mm/slab.c:3541
>  create_object+0x83/0x880 mm/kmemleak.c:578
>  kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline]
>  slab_post_alloc_hook mm/slab.h:442 [inline]
>  slab_alloc mm/slab.c:3381 [inline]
>  kmem_cache_alloc+0x18f/0x2f0 mm/slab.c:3541
>  mempool_alloc+0x13e/0x340 mm/mempool.c:385
>  bio_alloc_bioset+0x36f/0x5d0 block/bio.c:489
>  bio_alloc include/linux/bio.h:393 [inline]
>  submit_bh_wbc.isra.57+0x128/0x680 fs/buffer.c:3061
>  __block_write_full_page+0x6e8/0xcd0 fs/buffer.c:1765
>  block_write_full_page+0x202/0x250 fs/buffer.c:2955
>  pageout mm/vmscan.c:865 [inline]
>  shrink_page_list+0x220f/0x3800 mm/vmscan.c:1383
>  shrink_inactive_list+0x3c2/0xaa0 mm/vmscan.c:1961
>  shrink_list mm/vmscan.c:2273 [inline]
>  shrink_node_memcg.constprop.83+0x4bf/0x10e0 mm/vmscan.c:2538
>  shrink_node+0x162/0xd10 mm/vmscan.c:2753
>  kswapd_shrink_node mm/vmscan.c:3516 [inline]
>  balance_pgdat+0x47f/0xc00 mm/vmscan.c:3674
>  kswapd+0x57c/0xde0 mm/vmscan.c:3929
>  kthread+0x347/0x410 kernel/kthread.c:246
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
>
>
> Syzkaller reproducer:
> # {Threaded:false Collide:false Repeat:true RepeatTimes:0 Procs:8
> Sandbox:none Fault:false FaultCall:-1 FaultNth:0 EnableTun:false
> UseTmpDir:true EnableCgroups:false EnableNetdev:true ResetNet:false
> HandleSegv:false Repro:false Trace:false}
> unshare(0x40000000)
>
>
> C reproducer:
> // autogenerated by syzkaller (https://github.com/google/syzkaller)
>
> #define _GNU_SOURCE
>
> #include <arpa/inet.h>
> #include <dirent.h>
> #include <endian.h>
> #include <errno.h>
> #include <fcntl.h>
> #include <net/if.h>
> #include <net/if_arp.h>
> #include <netinet/in.h>
> #include <sched.h>
> #include <signal.h>
> #include <stdarg.h>
> #include <stdbool.h>
> #include <stdint.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/ioctl.h>
> #include <sys/mount.h>
> #include <sys/prctl.h>
> #include <sys/resource.h>
> #include <sys/socket.h>
> #include <sys/stat.h>
> #include <sys/syscall.h>
> #include <sys/time.h>
> #include <sys/types.h>
> #include <sys/uio.h>
> #include <sys/wait.h>
> #include <time.h>
> #include <unistd.h>
>
> #include <linux/if_addr.h>
> #include <linux/if_ether.h>
> #include <linux/if_link.h>
> #include <linux/if_tun.h>
> #include <linux/in6.h>
> #include <linux/ip.h>
> #include <linux/neighbour.h>
> #include <linux/net.h>
> #include <linux/netlink.h>
> #include <linux/rtnetlink.h>
> #include <linux/tcp.h>
> #include <linux/veth.h>
>
> unsigned long long procid;
>
> static void sleep_ms(uint64_t ms)
> {
>   usleep(ms * 1000);
> }
>
> static uint64_t current_time_ms(void)
> {
>   struct timespec ts;
>   if (clock_gettime(CLOCK_MONOTONIC, &ts))
>     exit(1);
>   return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
> }
>
> static void use_temporary_dir(void)
> {
>   char tmpdir_template[] = "./syzkaller.XXXXXX";
>   char* tmpdir = mkdtemp(tmpdir_template);
>   if (!tmpdir)
>     exit(1);
>   if (chmod(tmpdir, 0777))
>     exit(1);
>   if (chdir(tmpdir))
>     exit(1);
> }
>
> static bool write_file(const char* file, const char* what, ...)
> {
>   char buf[1024];
>   va_list args;
>   va_start(args, what);
>   vsnprintf(buf, sizeof(buf), what, args);
>   va_end(args);
>   buf[sizeof(buf) - 1] = 0;
>   int len = strlen(buf);
>   int fd = open(file, O_WRONLY | O_CLOEXEC);
>   if (fd == -1)
>     return false;
>   if (write(fd, buf, len) != len) {
>     int err = errno;
>     close(fd);
>     errno = err;
>     return false;
>   }
>   close(fd);
>   return true;
> }
>
> static struct {
>   char* pos;
>   int nesting;
>   struct nlattr* nested[8];
>   char buf[1024];
> } nlmsg;
>
> static void netlink_init(int typ, int flags, const void* data, int size)
> {
>   memset(&nlmsg, 0, sizeof(nlmsg));
>   struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;
>   hdr->nlmsg_type = typ;
>   hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;
>   memcpy(hdr + 1, data, size);
>   nlmsg.pos = (char*)(hdr + 1) + NLMSG_ALIGN(size);
> }
>
> static void netlink_attr(int typ, const void* data, int size)
> {
>   struct nlattr* attr = (struct nlattr*)nlmsg.pos;
>   attr->nla_len = sizeof(*attr) + size;
>   attr->nla_type = typ;
>   memcpy(attr + 1, data, size);
>   nlmsg.pos += NLMSG_ALIGN(attr->nla_len);
> }
>
> static void netlink_nest(int typ)
> {
>   struct nlattr* attr = (struct nlattr*)nlmsg.pos;
>   attr->nla_type = typ;
>   nlmsg.pos += sizeof(*attr);
>   nlmsg.nested[nlmsg.nesting++] = attr;
> }
>
> static void netlink_done(void)
> {
>   struct nlattr* attr = nlmsg.nested[--nlmsg.nesting];
>   attr->nla_len = nlmsg.pos - (char*)attr;
> }
>
> static int netlink_send(int sock)
> {
>   if (nlmsg.pos > nlmsg.buf + sizeof(nlmsg.buf) || nlmsg.nesting)
>     exit(1);
>   struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;
>   hdr->nlmsg_len = nlmsg.pos - nlmsg.buf;
>   struct sockaddr_nl addr;
>   memset(&addr, 0, sizeof(addr));
>   addr.nl_family = AF_NETLINK;
>   unsigned n = sendto(sock, nlmsg.buf, hdr->nlmsg_len, 0,
>                       (struct sockaddr*)&addr, sizeof(addr));
>   if (n != hdr->nlmsg_len)
>     exit(1);
>   n = recv(sock, nlmsg.buf, sizeof(nlmsg.buf), 0);
>   if (n < sizeof(struct nlmsghdr) + sizeof(struct nlmsgerr))
>     exit(1);
>   if (hdr->nlmsg_type != NLMSG_ERROR)
>     exit(1);
>   return -((struct nlmsgerr*)(hdr + 1))->error;
> }
>
> static void netlink_add_device_impl(const char* type, const char* name)
> {
>   struct ifinfomsg hdr;
>   memset(&hdr, 0, sizeof(hdr));
>   netlink_init(RTM_NEWLINK, NLM_F_EXCL | NLM_F_CREATE, &hdr, sizeof(hdr));
>   if (name)
>     netlink_attr(IFLA_IFNAME, name, strlen(name));
>   netlink_nest(IFLA_LINKINFO);
>   netlink_attr(IFLA_INFO_KIND, type, strlen(type));
> }
>
> static void netlink_add_device(int sock, const char* type, const char* name)
> {
>   netlink_add_device_impl(type, name);
>   netlink_done();
>   int err = netlink_send(sock);
>   (void)err;
> }
>
> static void netlink_add_veth(int sock, const char* name, const char* peer)
> {
>   netlink_add_device_impl("veth", name);
>   netlink_nest(IFLA_INFO_DATA);
>   netlink_nest(VETH_INFO_PEER);
>   nlmsg.pos += sizeof(struct ifinfomsg);
>   netlink_attr(IFLA_IFNAME, peer, strlen(peer));
>   netlink_done();
>   netlink_done();
>   netlink_done();
>   int err = netlink_send(sock);
>   (void)err;
> }
>
> static void netlink_add_hsr(int sock, const char* name, const char* slave1,
>                             const char* slave2)
> {
>   netlink_add_device_impl("hsr", name);
>   netlink_nest(IFLA_INFO_DATA);
>   int ifindex1 = if_nametoindex(slave1);
>   netlink_attr(IFLA_HSR_SLAVE1, &ifindex1, sizeof(ifindex1));
>   int ifindex2 = if_nametoindex(slave2);
>   netlink_attr(IFLA_HSR_SLAVE2, &ifindex2, sizeof(ifindex2));
>   netlink_done();
>   netlink_done();
>   int err = netlink_send(sock);
>   (void)err;
> }
>
> static void netlink_device_change(int sock, const char* name, bool up,
>                                   const char* master, const void* mac,
>                                   int macsize)
> {
>   struct ifinfomsg hdr;
>   memset(&hdr, 0, sizeof(hdr));
>   if (up)
>     hdr.ifi_flags = hdr.ifi_change = IFF_UP;
>   netlink_init(RTM_NEWLINK, 0, &hdr, sizeof(hdr));
>   netlink_attr(IFLA_IFNAME, name, strlen(name));
>   if (master) {
>     int ifindex = if_nametoindex(master);
>     netlink_attr(IFLA_MASTER, &ifindex, sizeof(ifindex));
>   }
>   if (macsize)
>     netlink_attr(IFLA_ADDRESS, mac, macsize);
>   int err = netlink_send(sock);
>   (void)err;
> }
>
> static int netlink_add_addr(int sock, const char* dev, const void* addr,
>                             int addrsize)
> {
>   struct ifaddrmsg hdr;
>   memset(&hdr, 0, sizeof(hdr));
>   hdr.ifa_family = addrsize == 4 ? AF_INET : AF_INET6;
>   hdr.ifa_prefixlen = addrsize == 4 ? 24 : 120;
>   hdr.ifa_scope = RT_SCOPE_UNIVERSE;
>   hdr.ifa_index = if_nametoindex(dev);
>   netlink_init(RTM_NEWADDR, NLM_F_CREATE | NLM_F_REPLACE, &hdr,
> sizeof(hdr));
>   netlink_attr(IFA_LOCAL, addr, addrsize);
>   netlink_attr(IFA_ADDRESS, addr, addrsize);
>   return netlink_send(sock);
> }
>
> static void netlink_add_addr4(int sock, const char* dev, const char* addr)
> {
>   struct in_addr in_addr;
>   inet_pton(AF_INET, addr, &in_addr);
>   int err = netlink_add_addr(sock, dev, &in_addr, sizeof(in_addr));
>   (void)err;
> }
>
> static void netlink_add_addr6(int sock, const char* dev, const char* addr)
> {
>   struct in6_addr in6_addr;
>   inet_pton(AF_INET6, addr, &in6_addr);
>   int err = netlink_add_addr(sock, dev, &in6_addr, sizeof(in6_addr));
>   (void)err;
> }
>
> #define DEV_IPV4 "172.20.20.%d"
> #define DEV_IPV6 "fe80::%02hx"
> #define DEV_MAC 0x00aaaaaaaaaa
> static void initialize_netdevices(void)
> {
>   char netdevsim[16];
>   sprintf(netdevsim, "netdevsim%d", (int)procid);
>   struct {
>     const char* type;
>     const char* dev;
>   } devtypes[] = {
>       {"ip6gretap", "ip6gretap0"}, {"bridge", "bridge0"},
>       {"vcan", "vcan0"},           {"bond", "bond0"},
>       {"team", "team0"},           {"dummy", "dummy0"},
>       {"nlmon", "nlmon0"},         {"caif", "caif0"},
>       {"batadv", "batadv0"},       {"vxcan", "vxcan1"},
>       {"netdevsim", netdevsim},    {"veth", 0},
>   };
>   const char* devmasters[] = {"bridge", "bond", "team"};
>   struct {
>     const char* name;
>     int macsize;
>     bool noipv6;
>   } devices[] = {
>       {"lo", ETH_ALEN},
>       {"sit0", 0},
>       {"bridge0", ETH_ALEN},
>       {"vcan0", 0, true},
>       {"tunl0", 0},
>       {"gre0", 0},
>       {"gretap0", ETH_ALEN},
>       {"ip_vti0", 0},
>       {"ip6_vti0", 0},
>       {"ip6tnl0", 0},
>       {"ip6gre0", 0},
>       {"ip6gretap0", ETH_ALEN},
>       {"erspan0", ETH_ALEN},
>       {"bond0", ETH_ALEN},
>       {"veth0", ETH_ALEN},
>       {"veth1", ETH_ALEN},
>       {"team0", ETH_ALEN},
>       {"veth0_to_bridge", ETH_ALEN},
>       {"veth1_to_bridge", ETH_ALEN},
>       {"veth0_to_bond", ETH_ALEN},
>       {"veth1_to_bond", ETH_ALEN},
>       {"veth0_to_team", ETH_ALEN},
>       {"veth1_to_team", ETH_ALEN},
>       {"veth0_to_hsr", ETH_ALEN},
>       {"veth1_to_hsr", ETH_ALEN},
>       {"hsr0", 0},
>       {"dummy0", ETH_ALEN},
>       {"nlmon0", 0},
>       {"vxcan1", 0, true},
>       {"caif0", ETH_ALEN},
>       {"batadv0", ETH_ALEN},
>       {netdevsim, ETH_ALEN},
>   };
>   int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
>   if (sock == -1)
>     exit(1);
>   unsigned i;
>   for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++)
>     netlink_add_device(sock, devtypes[i].type, devtypes[i].dev);
>   for (i = 0; i < sizeof(devmasters) / (sizeof(devmasters[0])); i++) {
>     char master[32], slave0[32], veth0[32], slave1[32], veth1[32];
>     sprintf(slave0, "%s_slave_0", devmasters[i]);
>     sprintf(veth0, "veth0_to_%s", devmasters[i]);
>     netlink_add_veth(sock, slave0, veth0);
>     sprintf(slave1, "%s_slave_1", devmasters[i]);
>     sprintf(veth1, "veth1_to_%s", devmasters[i]);
>     netlink_add_veth(sock, slave1, veth1);
>     sprintf(master, "%s0", devmasters[i]);
>     netlink_device_change(sock, slave0, false, master, 0, 0);
>     netlink_device_change(sock, slave1, false, master, 0, 0);
>   }
>   netlink_device_change(sock, "bridge_slave_0", true, 0, 0, 0);
>   netlink_device_change(sock, "bridge_slave_1", true, 0, 0, 0);
>   netlink_add_veth(sock, "hsr_slave_0", "veth0_to_hsr");
>   netlink_add_veth(sock, "hsr_slave_1", "veth1_to_hsr");
>   netlink_add_hsr(sock, "hsr0", "hsr_slave_0", "hsr_slave_1");
>   netlink_device_change(sock, "hsr_slave_0", true, 0, 0, 0);
>   netlink_device_change(sock, "hsr_slave_1", true, 0, 0, 0);
>   for (i = 0; i < sizeof(devices) / (sizeof(devices[0])); i++) {
>     char addr[32];
>     sprintf(addr, DEV_IPV4, i + 10);
>     netlink_add_addr4(sock, devices[i].name, addr);
>     if (!devices[i].noipv6) {
>       sprintf(addr, DEV_IPV6, i + 10);
>       netlink_add_addr6(sock, devices[i].name, addr);
>     }
>     uint64_t macaddr = DEV_MAC + ((i + 10ull) << 40);
>     netlink_device_change(sock, devices[i].name, true, 0, &macaddr,
>                           devices[i].macsize);
>   }
>   close(sock);
> }
> static void initialize_netdevices_init(void)
> {
>   int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
>   if (sock == -1)
>     exit(1);
>   struct {
>     const char* type;
>     int macsize;
>     bool noipv6;
>     bool noup;
>   } devtypes[] = {
>       {"nr", 7, true}, {"rose", 5, true, true},
>   };
>   unsigned i;
>   for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++) {
>     char dev[32], addr[32];
>     sprintf(dev, "%s%d", devtypes[i].type, (int)procid);
>     sprintf(addr, "172.30.%d.%d", i, (int)procid + 1);
>     netlink_add_addr4(sock, dev, addr);
>     if (!devtypes[i].noipv6) {
>       sprintf(addr, "fe88::%02hx:%02hx", i, (int)procid + 1);
>       netlink_add_addr6(sock, dev, addr);
>     }
>     int macsize = devtypes[i].macsize;
>     uint64_t macaddr = 0xbbbbbb +
>                        ((unsigned long long)i << (8 * (macsize - 2))) +
>                        (procid << (8 * (macsize - 1)));
>     netlink_device_change(sock, dev, !devtypes[i].noup, 0, &macaddr,
> macsize);
>   }
>   close(sock);
> }
>
> static void setup_common()
> {
>   if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
>   }
> }
>
> static void loop();
>
> static void sandbox_common()
> {
>   prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
>   setpgrp();
>   setsid();
>   struct rlimit rlim;
>   rlim.rlim_cur = rlim.rlim_max = 200 << 20;
>   setrlimit(RLIMIT_AS, &rlim);
>   rlim.rlim_cur = rlim.rlim_max = 32 << 20;
>   setrlimit(RLIMIT_MEMLOCK, &rlim);
>   rlim.rlim_cur = rlim.rlim_max = 136 << 20;
>   setrlimit(RLIMIT_FSIZE, &rlim);
>   rlim.rlim_cur = rlim.rlim_max = 1 << 20;
>   setrlimit(RLIMIT_STACK, &rlim);
>   rlim.rlim_cur = rlim.rlim_max = 0;
>   setrlimit(RLIMIT_CORE, &rlim);
>   rlim.rlim_cur = rlim.rlim_max = 256;
>   setrlimit(RLIMIT_NOFILE, &rlim);
>   if (unshare(CLONE_NEWNS)) {
>   }
>   if (unshare(CLONE_NEWIPC)) {
>   }
>   if (unshare(0x02000000)) {
>   }
>   if (unshare(CLONE_NEWUTS)) {
>   }
>   if (unshare(CLONE_SYSVSEM)) {
>   }
>   typedef struct {
>     const char* name;
>     const char* value;
>   } sysctl_t;
>   static const sysctl_t sysctls[] = {
>       {"/proc/sys/kernel/shmmax", "16777216"},
>       {"/proc/sys/kernel/shmall", "536870912"},
>       {"/proc/sys/kernel/shmmni", "1024"},
>       {"/proc/sys/kernel/msgmax", "8192"},
>       {"/proc/sys/kernel/msgmni", "1024"},
>       {"/proc/sys/kernel/msgmnb", "1024"},
>       {"/proc/sys/kernel/sem", "1024 1048576 500 1024"},
>   };
>   unsigned i;
>   for (i = 0; i < sizeof(sysctls) / sizeof(sysctls[0]); i++)
>     write_file(sysctls[i].name, sysctls[i].value);
> }
>
> int wait_for_loop(int pid)
> {
>   if (pid < 0)
>     exit(1);
>   int status = 0;
>   while (waitpid(-1, &status, __WALL) != pid) {
>   }
>   return WEXITSTATUS(status);
> }
>
> static int do_sandbox_none(void)
> {
>   if (unshare(CLONE_NEWPID)) {
>   }
>   int pid = fork();
>   if (pid != 0)
>     return wait_for_loop(pid);
>   setup_common();
>   sandbox_common();
>   initialize_netdevices_init();
>   if (unshare(CLONE_NEWNET)) {
>   }
>   initialize_netdevices();
>   loop();
>   exit(1);
> }
>
> #define FS_IOC_SETFLAGS _IOW('f', 2, long)
> static void remove_dir(const char* dir)
> {
>   DIR* dp;
>   struct dirent* ep;
>   int iter = 0;
> retry:
>   while (umount2(dir, MNT_DETACH) == 0) {
>   }
>   dp = opendir(dir);
>   if (dp == NULL) {
>     if (errno == EMFILE) {
>       exit(1);
>     }
>     exit(1);
>   }
>   while ((ep = readdir(dp))) {
>     if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0)
>       continue;
>     char filename[FILENAME_MAX];
>     snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name);
>     while (umount2(filename, MNT_DETACH) == 0) {
>     }
>     struct stat st;
>     if (lstat(filename, &st))
>       exit(1);
>     if (S_ISDIR(st.st_mode)) {
>       remove_dir(filename);
>       continue;
>     }
>     int i;
>     for (i = 0;; i++) {
>       if (unlink(filename) == 0)
>         break;
>       if (errno == EPERM) {
>         int fd = open(filename, O_RDONLY);
>         if (fd != -1) {
>           long flags = 0;
>           if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
>             close(fd);
>           continue;
>         }
>       }
>       if (errno == EROFS) {
>         break;
>       }
>       if (errno != EBUSY || i > 100)
>         exit(1);
>       if (umount2(filename, MNT_DETACH))
>         exit(1);
>     }
>   }
>   closedir(dp);
>   int i;
>   for (i = 0;; i++) {
>     if (rmdir(dir) == 0)
>       break;
>     if (i < 100) {
>       if (errno == EPERM) {
>         int fd = open(dir, O_RDONLY);
>         if (fd != -1) {
>           long flags = 0;
>           if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)
>             close(fd);
>           continue;
>         }
>       }
>       if (errno == EROFS) {
>         break;
>       }
>       if (errno == EBUSY) {
>         if (umount2(dir, MNT_DETACH))
>           exit(1);
>         continue;
>       }
>       if (errno == ENOTEMPTY) {
>         if (iter < 100) {
>           iter++;
>           goto retry;
>         }
>       }
>     }
>     exit(1);
>   }
> }
>
> static void kill_and_wait(int pid, int* status)
> {
>   kill(-pid, SIGKILL);
>   kill(pid, SIGKILL);
>   int i;
>   for (i = 0; i < 100; i++) {
>     if (waitpid(-1, status, WNOHANG | __WALL) == pid)
>       return;
>     usleep(1000);
>   }
>   DIR* dir = opendir("/sys/fs/fuse/connections");
>   if (dir) {
>     for (;;) {
>       struct dirent* ent = readdir(dir);
>       if (!ent)
>         break;
>       if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
>         continue;
>       char abort[300];
>       snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",
>                ent->d_name);
>       int fd = open(abort, O_WRONLY);
>       if (fd == -1) {
>         continue;
>       }
>       if (write(fd, abort, 1) < 0) {
>       }
>       close(fd);
>     }
>     closedir(dir);
>   } else {
>   }
>   while (waitpid(-1, status, __WALL) != pid) {
>   }
> }
>
> #define SYZ_HAVE_SETUP_TEST 1
> static void setup_test()
> {
>   prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
>   setpgrp();
> }
>
> #define SYZ_HAVE_RESET_TEST 1
> static void reset_test()
> {
>   int fd;
>   for (fd = 3; fd < 30; fd++)
>     close(fd);
> }
>
> static void execute_one(void);
>
> #define WAIT_FLAGS __WALL
>
> static void loop(void)
> {
>   int iter;
>   for (iter = 0;; iter++) {
>     char cwdbuf[32];
>     sprintf(cwdbuf, "./%d", iter);
>     if (mkdir(cwdbuf, 0777))
>       exit(1);
>     int pid = fork();
>     if (pid < 0)
>       exit(1);
>     if (pid == 0) {
>       if (chdir(cwdbuf))
>         exit(1);
>       setup_test();
>       execute_one();
>       reset_test();
>       exit(0);
>     }
>     int status = 0;
>     uint64_t start = current_time_ms();
>     for (;;) {
>       if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
>         break;
>       sleep_ms(1);
>       if (current_time_ms() - start < 5 * 1000)
>         continue;
>       kill_and_wait(pid, &status);
>       break;
>     }
>     remove_dir(cwdbuf);
>   }
> }
>
> void execute_one(void)
> {
>   syscall(__NR_unshare, 0x40000000);
> }
> int main(void)
> {
>   syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);
>   for (procid = 0; procid < 8; procid++) {
>     if (fork() == 0) {
>       use_temporary_dir();
>       do_sandbox_none();
>     }
>   }
>   sleep(1000000);
>   return 0;
> }
>
>
> I reviewed kernel code and found a bug that
> net_drop_ns func doesn't call net_free func when refcount_dec_and_test's
> return value is zero.

Yes.  We don't call net_free when the reference count does not decrement
to zero.  The reference count is initialized to 1 a few lines above the
section of code in your patch so that should not be a problem.

> or
> when rv = down_read_killable(&pernet_ops_rwsem) < 0, it doesn't need to
> call refcount_dec_and_test.

It doesn't need to but it should be harmless.

> https://github.com/torvalds/linux/commit/5ba049a5cc8e24a1643df75bbf65b4efa070fa74#diff-9312644e2968a45510bacdd2b2872ad2
> (I can't reproduce this bug on v4.15 , and
> 1bdbe227492075d058e37cb3d400e6468d0095b5 with my patch. Because of the
> previous version of kernel doesn't have this bug.)
> This bug can lead to memory leak or DOS.
>
> I made a patch for this bug. (just revert to a before commit)

What am I missing?

The only thing I can see your patch doing is covering up a memory stomp
that has the effect of changing the value of net->passive.  I am not
really keen on hiding bugs of that kind.


> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index b02fb19df2cc..9de0ade14956 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -431,15 +431,18 @@ struct net *copy_net_ns(unsigned long flags,
>         get_user_ns(user_ns);
>
>         rv = down_read_killable(&pernet_ops_rwsem);
> -       if (rv < 0)
> -               goto put_userns;
> +       if (rv < 0){
> +        net_free(net);
> +        dec_net_namespaces(ucounts);
> +        put_user_ns(user_ns);
> +        return ERR_PTR(rv);
> +    }
>
>         rv = setup_net(net, user_ns);
>
>         up_read(&pernet_ops_rwsem);
>
>         if (rv < 0) {
> -put_userns:
>                 put_user_ns(user_ns);
>                 net_drop_ns(net);
>  dec_ucounts:
>
> and, sorry for my encrypted mails.

Eric
Kirill Tkhai - Jan. 11, 2019, 8:41 p.m.
On 11.01.2019 23:33, Eric W. Biederman wrote:
> zzoru <zzoru007@gmail.com> writes:

> 

>> net/core: BUG in copy_net_ns() (net_namespace.c)

> 

> I don't understand this failure report at all.

> 

> I don't see the connection to copy_net_ns().  And I don't see how the

> suggested patch short of covering up a memory stomp could possibly make

> a difference.

> 

> What am I missing?


I received 3 spam messages from this address today.
We can simply ignore this report.

> 

> 

>> Hello,

>>

>> I've got the following error report while fuzzing the kernel with syzkaller.

>>

>> On commit 1bdbe227492075d058e37cb3d400e6468d0095b5

>>

>> Syzkaller hit 'WARNING in __alloc_pages_slowpath' bug.

>>

>> syz-executor561 (17453) used greatest stack depth: 25056 bytes left

>> WARNING: CPU: 0 PID: 692 at mm/page_alloc.c:4415

>> __alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4386

>> Kernel panic - not syncing: panic_on_warn set ...

>> CPU: 0 PID: 692 Comm: kswapd0 Not tainted 5.0.0-rc1+ #4

>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS

>> Ubuntu-1.8.2-1ubuntu1 04/01/2014

>> Call Trace:

>>  __dump_stack lib/dump_stack.c:77 [inline]

>>  dump_stack+0xca/0x13e lib/dump_stack.c:113

>>  panic+0x278/0x5bf kernel/panic.c:214

>>  __warn.cold.10+0x20/0x45 kernel/panic.c:571

>>  report_bug+0x246/0x2d0 lib/bug.c:186

>>  fixup_bug arch/x86/kernel/traps.c:178 [inline]

>>  do_error_trap+0x123/0x1e0 arch/x86/kernel/traps.c:271

>>  do_invalid_op+0x31/0x40 arch/x86/kernel/traps.c:290

>>  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973

>> RIP: 0010:__alloc_pages_slowpath+0x1cb1/0x2220 mm/page_alloc.c:4415

>> Code: 8b 84 24 a8 00 00 00 e9 ea f1 ff ff 85 d2 0f 85 0b 01 00 00 48 c7

>> c7 c0 5e 55 84 e8 79 f8 23 02 e9 86 f9 ff ff 44 8b 74 24 0c <0f> 0b 48

>> b8 00 00 00 00 00 fc ff df 48 8b 54 24 18 48 c1 ea 03 80

>> RSP: 0018:ffff8880683fedb8 EFLAGS: 00010046

>> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffff1100d07fda4

>> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88807ffdd528

>> RBP: dffffc0000000000 R08: 0000000000000000 R09: 000000000000067a

>> R10: 0000000000000000 R11: ffff88807ffdc487 R12: 0000000000000000

>> R13: ffff8880683ff010 R14: 0000000000415a00 R15: ffff8880683ff010

>>  __alloc_pages_nodemask+0x521/0x5f0 mm/page_alloc.c:4555

>>  __alloc_pages include/linux/gfp.h:473 [inline]

>>  __alloc_pages_node include/linux/gfp.h:486 [inline]

>>  kmem_getpages mm/slab.c:1398 [inline]

>>  cache_grow_begin+0x95/0x300 mm/slab.c:2666

>>  fallback_alloc+0x1ce/0x270 mm/slab.c:3208

>>  __do_cache_alloc mm/slab.c:3345 [inline]

>>  slab_alloc mm/slab.c:3373 [inline]

>>  kmem_cache_alloc+0x286/0x2f0 mm/slab.c:3541

>>  create_object+0x83/0x880 mm/kmemleak.c:578

>>  kmemleak_alloc_recursive include/linux/kmemleak.h:55 [inline]

>>  slab_post_alloc_hook mm/slab.h:442 [inline]

>>  slab_alloc mm/slab.c:3381 [inline]

>>  kmem_cache_alloc+0x18f/0x2f0 mm/slab.c:3541

>>  mempool_alloc+0x13e/0x340 mm/mempool.c:385

>>  bio_alloc_bioset+0x36f/0x5d0 block/bio.c:489

>>  bio_alloc include/linux/bio.h:393 [inline]

>>  submit_bh_wbc.isra.57+0x128/0x680 fs/buffer.c:3061

>>  __block_write_full_page+0x6e8/0xcd0 fs/buffer.c:1765

>>  block_write_full_page+0x202/0x250 fs/buffer.c:2955

>>  pageout mm/vmscan.c:865 [inline]

>>  shrink_page_list+0x220f/0x3800 mm/vmscan.c:1383

>>  shrink_inactive_list+0x3c2/0xaa0 mm/vmscan.c:1961

>>  shrink_list mm/vmscan.c:2273 [inline]

>>  shrink_node_memcg.constprop.83+0x4bf/0x10e0 mm/vmscan.c:2538

>>  shrink_node+0x162/0xd10 mm/vmscan.c:2753

>>  kswapd_shrink_node mm/vmscan.c:3516 [inline]

>>  balance_pgdat+0x47f/0xc00 mm/vmscan.c:3674

>>  kswapd+0x57c/0xde0 mm/vmscan.c:3929

>>  kthread+0x347/0x410 kernel/kthread.c:246

>>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

>> Dumping ftrace buffer:

>>    (ftrace buffer empty)

>> Kernel Offset: disabled

>> Rebooting in 86400 seconds..

>>

>>

>> Syzkaller reproducer:

>> # {Threaded:false Collide:false Repeat:true RepeatTimes:0 Procs:8

>> Sandbox:none Fault:false FaultCall:-1 FaultNth:0 EnableTun:false

>> UseTmpDir:true EnableCgroups:false EnableNetdev:true ResetNet:false

>> HandleSegv:false Repro:false Trace:false}

>> unshare(0x40000000)

>>

>>

>> C reproducer:

>> // autogenerated by syzkaller (https://github.com/google/syzkaller)

>>

>> #define _GNU_SOURCE

>>

>> #include <arpa/inet.h>

>> #include <dirent.h>

>> #include <endian.h>

>> #include <errno.h>

>> #include <fcntl.h>

>> #include <net/if.h>

>> #include <net/if_arp.h>

>> #include <netinet/in.h>

>> #include <sched.h>

>> #include <signal.h>

>> #include <stdarg.h>

>> #include <stdbool.h>

>> #include <stdint.h>

>> #include <stdio.h>

>> #include <stdlib.h>

>> #include <string.h>

>> #include <sys/ioctl.h>

>> #include <sys/mount.h>

>> #include <sys/prctl.h>

>> #include <sys/resource.h>

>> #include <sys/socket.h>

>> #include <sys/stat.h>

>> #include <sys/syscall.h>

>> #include <sys/time.h>

>> #include <sys/types.h>

>> #include <sys/uio.h>

>> #include <sys/wait.h>

>> #include <time.h>

>> #include <unistd.h>

>>

>> #include <linux/if_addr.h>

>> #include <linux/if_ether.h>

>> #include <linux/if_link.h>

>> #include <linux/if_tun.h>

>> #include <linux/in6.h>

>> #include <linux/ip.h>

>> #include <linux/neighbour.h>

>> #include <linux/net.h>

>> #include <linux/netlink.h>

>> #include <linux/rtnetlink.h>

>> #include <linux/tcp.h>

>> #include <linux/veth.h>

>>

>> unsigned long long procid;

>>

>> static void sleep_ms(uint64_t ms)

>> {

>>   usleep(ms * 1000);

>> }

>>

>> static uint64_t current_time_ms(void)

>> {

>>   struct timespec ts;

>>   if (clock_gettime(CLOCK_MONOTONIC, &ts))

>>     exit(1);

>>   return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;

>> }

>>

>> static void use_temporary_dir(void)

>> {

>>   char tmpdir_template[] = "./syzkaller.XXXXXX";

>>   char* tmpdir = mkdtemp(tmpdir_template);

>>   if (!tmpdir)

>>     exit(1);

>>   if (chmod(tmpdir, 0777))

>>     exit(1);

>>   if (chdir(tmpdir))

>>     exit(1);

>> }

>>

>> static bool write_file(const char* file, const char* what, ...)

>> {

>>   char buf[1024];

>>   va_list args;

>>   va_start(args, what);

>>   vsnprintf(buf, sizeof(buf), what, args);

>>   va_end(args);

>>   buf[sizeof(buf) - 1] = 0;

>>   int len = strlen(buf);

>>   int fd = open(file, O_WRONLY | O_CLOEXEC);

>>   if (fd == -1)

>>     return false;

>>   if (write(fd, buf, len) != len) {

>>     int err = errno;

>>     close(fd);

>>     errno = err;

>>     return false;

>>   }

>>   close(fd);

>>   return true;

>> }

>>

>> static struct {

>>   char* pos;

>>   int nesting;

>>   struct nlattr* nested[8];

>>   char buf[1024];

>> } nlmsg;

>>

>> static void netlink_init(int typ, int flags, const void* data, int size)

>> {

>>   memset(&nlmsg, 0, sizeof(nlmsg));

>>   struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;

>>   hdr->nlmsg_type = typ;

>>   hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | flags;

>>   memcpy(hdr + 1, data, size);

>>   nlmsg.pos = (char*)(hdr + 1) + NLMSG_ALIGN(size);

>> }

>>

>> static void netlink_attr(int typ, const void* data, int size)

>> {

>>   struct nlattr* attr = (struct nlattr*)nlmsg.pos;

>>   attr->nla_len = sizeof(*attr) + size;

>>   attr->nla_type = typ;

>>   memcpy(attr + 1, data, size);

>>   nlmsg.pos += NLMSG_ALIGN(attr->nla_len);

>> }

>>

>> static void netlink_nest(int typ)

>> {

>>   struct nlattr* attr = (struct nlattr*)nlmsg.pos;

>>   attr->nla_type = typ;

>>   nlmsg.pos += sizeof(*attr);

>>   nlmsg.nested[nlmsg.nesting++] = attr;

>> }

>>

>> static void netlink_done(void)

>> {

>>   struct nlattr* attr = nlmsg.nested[--nlmsg.nesting];

>>   attr->nla_len = nlmsg.pos - (char*)attr;

>> }

>>

>> static int netlink_send(int sock)

>> {

>>   if (nlmsg.pos > nlmsg.buf + sizeof(nlmsg.buf) || nlmsg.nesting)

>>     exit(1);

>>   struct nlmsghdr* hdr = (struct nlmsghdr*)nlmsg.buf;

>>   hdr->nlmsg_len = nlmsg.pos - nlmsg.buf;

>>   struct sockaddr_nl addr;

>>   memset(&addr, 0, sizeof(addr));

>>   addr.nl_family = AF_NETLINK;

>>   unsigned n = sendto(sock, nlmsg.buf, hdr->nlmsg_len, 0,

>>                       (struct sockaddr*)&addr, sizeof(addr));

>>   if (n != hdr->nlmsg_len)

>>     exit(1);

>>   n = recv(sock, nlmsg.buf, sizeof(nlmsg.buf), 0);

>>   if (n < sizeof(struct nlmsghdr) + sizeof(struct nlmsgerr))

>>     exit(1);

>>   if (hdr->nlmsg_type != NLMSG_ERROR)

>>     exit(1);

>>   return -((struct nlmsgerr*)(hdr + 1))->error;

>> }

>>

>> static void netlink_add_device_impl(const char* type, const char* name)

>> {

>>   struct ifinfomsg hdr;

>>   memset(&hdr, 0, sizeof(hdr));

>>   netlink_init(RTM_NEWLINK, NLM_F_EXCL | NLM_F_CREATE, &hdr, sizeof(hdr));

>>   if (name)

>>     netlink_attr(IFLA_IFNAME, name, strlen(name));

>>   netlink_nest(IFLA_LINKINFO);

>>   netlink_attr(IFLA_INFO_KIND, type, strlen(type));

>> }

>>

>> static void netlink_add_device(int sock, const char* type, const char* name)

>> {

>>   netlink_add_device_impl(type, name);

>>   netlink_done();

>>   int err = netlink_send(sock);

>>   (void)err;

>> }

>>

>> static void netlink_add_veth(int sock, const char* name, const char* peer)

>> {

>>   netlink_add_device_impl("veth", name);

>>   netlink_nest(IFLA_INFO_DATA);

>>   netlink_nest(VETH_INFO_PEER);

>>   nlmsg.pos += sizeof(struct ifinfomsg);

>>   netlink_attr(IFLA_IFNAME, peer, strlen(peer));

>>   netlink_done();

>>   netlink_done();

>>   netlink_done();

>>   int err = netlink_send(sock);

>>   (void)err;

>> }

>>

>> static void netlink_add_hsr(int sock, const char* name, const char* slave1,

>>                             const char* slave2)

>> {

>>   netlink_add_device_impl("hsr", name);

>>   netlink_nest(IFLA_INFO_DATA);

>>   int ifindex1 = if_nametoindex(slave1);

>>   netlink_attr(IFLA_HSR_SLAVE1, &ifindex1, sizeof(ifindex1));

>>   int ifindex2 = if_nametoindex(slave2);

>>   netlink_attr(IFLA_HSR_SLAVE2, &ifindex2, sizeof(ifindex2));

>>   netlink_done();

>>   netlink_done();

>>   int err = netlink_send(sock);

>>   (void)err;

>> }

>>

>> static void netlink_device_change(int sock, const char* name, bool up,

>>                                   const char* master, const void* mac,

>>                                   int macsize)

>> {

>>   struct ifinfomsg hdr;

>>   memset(&hdr, 0, sizeof(hdr));

>>   if (up)

>>     hdr.ifi_flags = hdr.ifi_change = IFF_UP;

>>   netlink_init(RTM_NEWLINK, 0, &hdr, sizeof(hdr));

>>   netlink_attr(IFLA_IFNAME, name, strlen(name));

>>   if (master) {

>>     int ifindex = if_nametoindex(master);

>>     netlink_attr(IFLA_MASTER, &ifindex, sizeof(ifindex));

>>   }

>>   if (macsize)

>>     netlink_attr(IFLA_ADDRESS, mac, macsize);

>>   int err = netlink_send(sock);

>>   (void)err;

>> }

>>

>> static int netlink_add_addr(int sock, const char* dev, const void* addr,

>>                             int addrsize)

>> {

>>   struct ifaddrmsg hdr;

>>   memset(&hdr, 0, sizeof(hdr));

>>   hdr.ifa_family = addrsize == 4 ? AF_INET : AF_INET6;

>>   hdr.ifa_prefixlen = addrsize == 4 ? 24 : 120;

>>   hdr.ifa_scope = RT_SCOPE_UNIVERSE;

>>   hdr.ifa_index = if_nametoindex(dev);

>>   netlink_init(RTM_NEWADDR, NLM_F_CREATE | NLM_F_REPLACE, &hdr,

>> sizeof(hdr));

>>   netlink_attr(IFA_LOCAL, addr, addrsize);

>>   netlink_attr(IFA_ADDRESS, addr, addrsize);

>>   return netlink_send(sock);

>> }

>>

>> static void netlink_add_addr4(int sock, const char* dev, const char* addr)

>> {

>>   struct in_addr in_addr;

>>   inet_pton(AF_INET, addr, &in_addr);

>>   int err = netlink_add_addr(sock, dev, &in_addr, sizeof(in_addr));

>>   (void)err;

>> }

>>

>> static void netlink_add_addr6(int sock, const char* dev, const char* addr)

>> {

>>   struct in6_addr in6_addr;

>>   inet_pton(AF_INET6, addr, &in6_addr);

>>   int err = netlink_add_addr(sock, dev, &in6_addr, sizeof(in6_addr));

>>   (void)err;

>> }

>>

>> #define DEV_IPV4 "172.20.20.%d"

>> #define DEV_IPV6 "fe80::%02hx"

>> #define DEV_MAC 0x00aaaaaaaaaa

>> static void initialize_netdevices(void)

>> {

>>   char netdevsim[16];

>>   sprintf(netdevsim, "netdevsim%d", (int)procid);

>>   struct {

>>     const char* type;

>>     const char* dev;

>>   } devtypes[] = {

>>       {"ip6gretap", "ip6gretap0"}, {"bridge", "bridge0"},

>>       {"vcan", "vcan0"},           {"bond", "bond0"},

>>       {"team", "team0"},           {"dummy", "dummy0"},

>>       {"nlmon", "nlmon0"},         {"caif", "caif0"},

>>       {"batadv", "batadv0"},       {"vxcan", "vxcan1"},

>>       {"netdevsim", netdevsim},    {"veth", 0},

>>   };

>>   const char* devmasters[] = {"bridge", "bond", "team"};

>>   struct {

>>     const char* name;

>>     int macsize;

>>     bool noipv6;

>>   } devices[] = {

>>       {"lo", ETH_ALEN},

>>       {"sit0", 0},

>>       {"bridge0", ETH_ALEN},

>>       {"vcan0", 0, true},

>>       {"tunl0", 0},

>>       {"gre0", 0},

>>       {"gretap0", ETH_ALEN},

>>       {"ip_vti0", 0},

>>       {"ip6_vti0", 0},

>>       {"ip6tnl0", 0},

>>       {"ip6gre0", 0},

>>       {"ip6gretap0", ETH_ALEN},

>>       {"erspan0", ETH_ALEN},

>>       {"bond0", ETH_ALEN},

>>       {"veth0", ETH_ALEN},

>>       {"veth1", ETH_ALEN},

>>       {"team0", ETH_ALEN},

>>       {"veth0_to_bridge", ETH_ALEN},

>>       {"veth1_to_bridge", ETH_ALEN},

>>       {"veth0_to_bond", ETH_ALEN},

>>       {"veth1_to_bond", ETH_ALEN},

>>       {"veth0_to_team", ETH_ALEN},

>>       {"veth1_to_team", ETH_ALEN},

>>       {"veth0_to_hsr", ETH_ALEN},

>>       {"veth1_to_hsr", ETH_ALEN},

>>       {"hsr0", 0},

>>       {"dummy0", ETH_ALEN},

>>       {"nlmon0", 0},

>>       {"vxcan1", 0, true},

>>       {"caif0", ETH_ALEN},

>>       {"batadv0", ETH_ALEN},

>>       {netdevsim, ETH_ALEN},

>>   };

>>   int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);

>>   if (sock == -1)

>>     exit(1);

>>   unsigned i;

>>   for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++)

>>     netlink_add_device(sock, devtypes[i].type, devtypes[i].dev);

>>   for (i = 0; i < sizeof(devmasters) / (sizeof(devmasters[0])); i++) {

>>     char master[32], slave0[32], veth0[32], slave1[32], veth1[32];

>>     sprintf(slave0, "%s_slave_0", devmasters[i]);

>>     sprintf(veth0, "veth0_to_%s", devmasters[i]);

>>     netlink_add_veth(sock, slave0, veth0);

>>     sprintf(slave1, "%s_slave_1", devmasters[i]);

>>     sprintf(veth1, "veth1_to_%s", devmasters[i]);

>>     netlink_add_veth(sock, slave1, veth1);

>>     sprintf(master, "%s0", devmasters[i]);

>>     netlink_device_change(sock, slave0, false, master, 0, 0);

>>     netlink_device_change(sock, slave1, false, master, 0, 0);

>>   }

>>   netlink_device_change(sock, "bridge_slave_0", true, 0, 0, 0);

>>   netlink_device_change(sock, "bridge_slave_1", true, 0, 0, 0);

>>   netlink_add_veth(sock, "hsr_slave_0", "veth0_to_hsr");

>>   netlink_add_veth(sock, "hsr_slave_1", "veth1_to_hsr");

>>   netlink_add_hsr(sock, "hsr0", "hsr_slave_0", "hsr_slave_1");

>>   netlink_device_change(sock, "hsr_slave_0", true, 0, 0, 0);

>>   netlink_device_change(sock, "hsr_slave_1", true, 0, 0, 0);

>>   for (i = 0; i < sizeof(devices) / (sizeof(devices[0])); i++) {

>>     char addr[32];

>>     sprintf(addr, DEV_IPV4, i + 10);

>>     netlink_add_addr4(sock, devices[i].name, addr);

>>     if (!devices[i].noipv6) {

>>       sprintf(addr, DEV_IPV6, i + 10);

>>       netlink_add_addr6(sock, devices[i].name, addr);

>>     }

>>     uint64_t macaddr = DEV_MAC + ((i + 10ull) << 40);

>>     netlink_device_change(sock, devices[i].name, true, 0, &macaddr,

>>                           devices[i].macsize);

>>   }

>>   close(sock);

>> }

>> static void initialize_netdevices_init(void)

>> {

>>   int sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);

>>   if (sock == -1)

>>     exit(1);

>>   struct {

>>     const char* type;

>>     int macsize;

>>     bool noipv6;

>>     bool noup;

>>   } devtypes[] = {

>>       {"nr", 7, true}, {"rose", 5, true, true},

>>   };

>>   unsigned i;

>>   for (i = 0; i < sizeof(devtypes) / sizeof(devtypes[0]); i++) {

>>     char dev[32], addr[32];

>>     sprintf(dev, "%s%d", devtypes[i].type, (int)procid);

>>     sprintf(addr, "172.30.%d.%d", i, (int)procid + 1);

>>     netlink_add_addr4(sock, dev, addr);

>>     if (!devtypes[i].noipv6) {

>>       sprintf(addr, "fe88::%02hx:%02hx", i, (int)procid + 1);

>>       netlink_add_addr6(sock, dev, addr);

>>     }

>>     int macsize = devtypes[i].macsize;

>>     uint64_t macaddr = 0xbbbbbb +

>>                        ((unsigned long long)i << (8 * (macsize - 2))) +

>>                        (procid << (8 * (macsize - 1)));

>>     netlink_device_change(sock, dev, !devtypes[i].noup, 0, &macaddr,

>> macsize);

>>   }

>>   close(sock);

>> }

>>

>> static void setup_common()

>> {

>>   if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {

>>   }

>> }

>>

>> static void loop();

>>

>> static void sandbox_common()

>> {

>>   prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);

>>   setpgrp();

>>   setsid();

>>   struct rlimit rlim;

>>   rlim.rlim_cur = rlim.rlim_max = 200 << 20;

>>   setrlimit(RLIMIT_AS, &rlim);

>>   rlim.rlim_cur = rlim.rlim_max = 32 << 20;

>>   setrlimit(RLIMIT_MEMLOCK, &rlim);

>>   rlim.rlim_cur = rlim.rlim_max = 136 << 20;

>>   setrlimit(RLIMIT_FSIZE, &rlim);

>>   rlim.rlim_cur = rlim.rlim_max = 1 << 20;

>>   setrlimit(RLIMIT_STACK, &rlim);

>>   rlim.rlim_cur = rlim.rlim_max = 0;

>>   setrlimit(RLIMIT_CORE, &rlim);

>>   rlim.rlim_cur = rlim.rlim_max = 256;

>>   setrlimit(RLIMIT_NOFILE, &rlim);

>>   if (unshare(CLONE_NEWNS)) {

>>   }

>>   if (unshare(CLONE_NEWIPC)) {

>>   }

>>   if (unshare(0x02000000)) {

>>   }

>>   if (unshare(CLONE_NEWUTS)) {

>>   }

>>   if (unshare(CLONE_SYSVSEM)) {

>>   }

>>   typedef struct {

>>     const char* name;

>>     const char* value;

>>   } sysctl_t;

>>   static const sysctl_t sysctls[] = {

>>       {"/proc/sys/kernel/shmmax", "16777216"},

>>       {"/proc/sys/kernel/shmall", "536870912"},

>>       {"/proc/sys/kernel/shmmni", "1024"},

>>       {"/proc/sys/kernel/msgmax", "8192"},

>>       {"/proc/sys/kernel/msgmni", "1024"},

>>       {"/proc/sys/kernel/msgmnb", "1024"},

>>       {"/proc/sys/kernel/sem", "1024 1048576 500 1024"},

>>   };

>>   unsigned i;

>>   for (i = 0; i < sizeof(sysctls) / sizeof(sysctls[0]); i++)

>>     write_file(sysctls[i].name, sysctls[i].value);

>> }

>>

>> int wait_for_loop(int pid)

>> {

>>   if (pid < 0)

>>     exit(1);

>>   int status = 0;

>>   while (waitpid(-1, &status, __WALL) != pid) {

>>   }

>>   return WEXITSTATUS(status);

>> }

>>

>> static int do_sandbox_none(void)

>> {

>>   if (unshare(CLONE_NEWPID)) {

>>   }

>>   int pid = fork();

>>   if (pid != 0)

>>     return wait_for_loop(pid);

>>   setup_common();

>>   sandbox_common();

>>   initialize_netdevices_init();

>>   if (unshare(CLONE_NEWNET)) {

>>   }

>>   initialize_netdevices();

>>   loop();

>>   exit(1);

>> }

>>

>> #define FS_IOC_SETFLAGS _IOW('f', 2, long)

>> static void remove_dir(const char* dir)

>> {

>>   DIR* dp;

>>   struct dirent* ep;

>>   int iter = 0;

>> retry:

>>   while (umount2(dir, MNT_DETACH) == 0) {

>>   }

>>   dp = opendir(dir);

>>   if (dp == NULL) {

>>     if (errno == EMFILE) {

>>       exit(1);

>>     }

>>     exit(1);

>>   }

>>   while ((ep = readdir(dp))) {

>>     if (strcmp(ep->d_name, ".") == 0 || strcmp(ep->d_name, "..") == 0)

>>       continue;

>>     char filename[FILENAME_MAX];

>>     snprintf(filename, sizeof(filename), "%s/%s", dir, ep->d_name);

>>     while (umount2(filename, MNT_DETACH) == 0) {

>>     }

>>     struct stat st;

>>     if (lstat(filename, &st))

>>       exit(1);

>>     if (S_ISDIR(st.st_mode)) {

>>       remove_dir(filename);

>>       continue;

>>     }

>>     int i;

>>     for (i = 0;; i++) {

>>       if (unlink(filename) == 0)

>>         break;

>>       if (errno == EPERM) {

>>         int fd = open(filename, O_RDONLY);

>>         if (fd != -1) {

>>           long flags = 0;

>>           if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)

>>             close(fd);

>>           continue;

>>         }

>>       }

>>       if (errno == EROFS) {

>>         break;

>>       }

>>       if (errno != EBUSY || i > 100)

>>         exit(1);

>>       if (umount2(filename, MNT_DETACH))

>>         exit(1);

>>     }

>>   }

>>   closedir(dp);

>>   int i;

>>   for (i = 0;; i++) {

>>     if (rmdir(dir) == 0)

>>       break;

>>     if (i < 100) {

>>       if (errno == EPERM) {

>>         int fd = open(dir, O_RDONLY);

>>         if (fd != -1) {

>>           long flags = 0;

>>           if (ioctl(fd, FS_IOC_SETFLAGS, &flags) == 0)

>>             close(fd);

>>           continue;

>>         }

>>       }

>>       if (errno == EROFS) {

>>         break;

>>       }

>>       if (errno == EBUSY) {

>>         if (umount2(dir, MNT_DETACH))

>>           exit(1);

>>         continue;

>>       }

>>       if (errno == ENOTEMPTY) {

>>         if (iter < 100) {

>>           iter++;

>>           goto retry;

>>         }

>>       }

>>     }

>>     exit(1);

>>   }

>> }

>>

>> static void kill_and_wait(int pid, int* status)

>> {

>>   kill(-pid, SIGKILL);

>>   kill(pid, SIGKILL);

>>   int i;

>>   for (i = 0; i < 100; i++) {

>>     if (waitpid(-1, status, WNOHANG | __WALL) == pid)

>>       return;

>>     usleep(1000);

>>   }

>>   DIR* dir = opendir("/sys/fs/fuse/connections");

>>   if (dir) {

>>     for (;;) {

>>       struct dirent* ent = readdir(dir);

>>       if (!ent)

>>         break;

>>       if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)

>>         continue;

>>       char abort[300];

>>       snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort",

>>                ent->d_name);

>>       int fd = open(abort, O_WRONLY);

>>       if (fd == -1) {

>>         continue;

>>       }

>>       if (write(fd, abort, 1) < 0) {

>>       }

>>       close(fd);

>>     }

>>     closedir(dir);

>>   } else {

>>   }

>>   while (waitpid(-1, status, __WALL) != pid) {

>>   }

>> }

>>

>> #define SYZ_HAVE_SETUP_TEST 1

>> static void setup_test()

>> {

>>   prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);

>>   setpgrp();

>> }

>>

>> #define SYZ_HAVE_RESET_TEST 1

>> static void reset_test()

>> {

>>   int fd;

>>   for (fd = 3; fd < 30; fd++)

>>     close(fd);

>> }

>>

>> static void execute_one(void);

>>

>> #define WAIT_FLAGS __WALL

>>

>> static void loop(void)

>> {

>>   int iter;

>>   for (iter = 0;; iter++) {

>>     char cwdbuf[32];

>>     sprintf(cwdbuf, "./%d", iter);

>>     if (mkdir(cwdbuf, 0777))

>>       exit(1);

>>     int pid = fork();

>>     if (pid < 0)

>>       exit(1);

>>     if (pid == 0) {

>>       if (chdir(cwdbuf))

>>         exit(1);

>>       setup_test();

>>       execute_one();

>>       reset_test();

>>       exit(0);

>>     }

>>     int status = 0;

>>     uint64_t start = current_time_ms();

>>     for (;;) {

>>       if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)

>>         break;

>>       sleep_ms(1);

>>       if (current_time_ms() - start < 5 * 1000)

>>         continue;

>>       kill_and_wait(pid, &status);

>>       break;

>>     }

>>     remove_dir(cwdbuf);

>>   }

>> }

>>

>> void execute_one(void)

>> {

>>   syscall(__NR_unshare, 0x40000000);

>> }

>> int main(void)

>> {

>>   syscall(__NR_mmap, 0x20000000, 0x1000000, 3, 0x32, -1, 0);

>>   for (procid = 0; procid < 8; procid++) {

>>     if (fork() == 0) {

>>       use_temporary_dir();

>>       do_sandbox_none();

>>     }

>>   }

>>   sleep(1000000);

>>   return 0;

>> }

>>

>>

>> I reviewed kernel code and found a bug that

>> net_drop_ns func doesn't call net_free func when refcount_dec_and_test's

>> return value is zero.

> 

> Yes.  We don't call net_free when the reference count does not decrement

> to zero.  The reference count is initialized to 1 a few lines above the

> section of code in your patch so that should not be a problem.

> 

>> or

>> when rv = down_read_killable(&pernet_ops_rwsem) < 0, it doesn't need to

>> call refcount_dec_and_test.

> 

> It doesn't need to but it should be harmless.

> 

>> https://github.com/torvalds/linux/commit/5ba049a5cc8e24a1643df75bbf65b4efa070fa74#diff-9312644e2968a45510bacdd2b2872ad2

>> (I can't reproduce this bug on v4.15 , and

>> 1bdbe227492075d058e37cb3d400e6468d0095b5 with my patch. Because of the

>> previous version of kernel doesn't have this bug.)

>> This bug can lead to memory leak or DOS.

>>

>> I made a patch for this bug. (just revert to a before commit)

> 

> What am I missing?

> 

> The only thing I can see your patch doing is covering up a memory stomp

> that has the effect of changing the value of net->passive.  I am not

> really keen on hiding bugs of that kind.

> 

> 

>> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c

>> index b02fb19df2cc..9de0ade14956 100644

>> --- a/net/core/net_namespace.c

>> +++ b/net/core/net_namespace.c

>> @@ -431,15 +431,18 @@ struct net *copy_net_ns(unsigned long flags,

>>         get_user_ns(user_ns);

>>

>>         rv = down_read_killable(&pernet_ops_rwsem);

>> -       if (rv < 0)

>> -               goto put_userns;

>> +       if (rv < 0){

>> +        net_free(net);

>> +        dec_net_namespaces(ucounts);

>> +        put_user_ns(user_ns);

>> +        return ERR_PTR(rv);

>> +    }

>>

>>         rv = setup_net(net, user_ns);

>>

>>         up_read(&pernet_ops_rwsem);

>>

>>         if (rv < 0) {

>> -put_userns:

>>                 put_user_ns(user_ns);

>>                 net_drop_ns(net);

>>  dec_ucounts:

>>

>> and, sorry for my encrypted mails.

> 

> Eric

>

Patch

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index b02fb19df2cc..9de0ade14956 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -431,15 +431,18 @@  struct net *copy_net_ns(unsigned long flags,
        get_user_ns(user_ns);

        rv = down_read_killable(&pernet_ops_rwsem);
-       if (rv < 0)
-               goto put_userns;
+       if (rv < 0){
+        net_free(net);
+        dec_net_namespaces(ucounts);
+        put_user_ns(user_ns);
+        return ERR_PTR(rv);
+    }

        rv = setup_net(net, user_ns);

        up_read(&pernet_ops_rwsem);

        if (rv < 0) {
-put_userns:
                put_user_ns(user_ns);
                net_drop_ns(net);
 dec_ucounts: