Patchwork [net] fou, fou6: do not assume linear skbs

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Submitter Eric Dumazet
Date Jan. 11, 2019, 12:55 p.m.
Message ID <20190111125552.148871-1-edumazet@google.com>
Download mbox | patch
Permalink /patch/697667/
State New
Headers show

Comments

Eric Dumazet - Jan. 11, 2019, 12:55 p.m.
Both gue_err() and gue6_err() incorrectly assume
linear skbs. Fix them to use pskb_may_pull().

BUG: KMSAN: uninit-value in gue6_err+0x475/0xc40 net/ipv6/fou6.c:101
CPU: 0 PID: 18083 Comm: syz-executor1 Not tainted 5.0.0-rc1+ #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x173/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x12e/0x2a0 mm/kmsan/kmsan.c:600
 __msan_warning+0x82/0xf0 mm/kmsan/kmsan_instr.c:313
 gue6_err+0x475/0xc40 net/ipv6/fou6.c:101
 __udp6_lib_err_encap_no_sk net/ipv6/udp.c:434 [inline]
 __udp6_lib_err_encap net/ipv6/udp.c:491 [inline]
 __udp6_lib_err+0x18d0/0x2590 net/ipv6/udp.c:522
 udplitev6_err+0x118/0x130 net/ipv6/udplite.c:27
 icmpv6_notify+0x462/0x9f0 net/ipv6/icmp.c:784
 icmpv6_rcv+0x18ac/0x3fa0 net/ipv6/icmp.c:872
 ip6_protocol_deliver_rcu+0xb5a/0x23a0 net/ipv6/ip6_input.c:394
 ip6_input_finish net/ipv6/ip6_input.c:434 [inline]
 NF_HOOK include/linux/netfilter.h:289 [inline]
 ip6_input+0x2b6/0x350 net/ipv6/ip6_input.c:443
 dst_input include/net/dst.h:450 [inline]
 ip6_rcv_finish+0x4e7/0x6d0 net/ipv6/ip6_input.c:76
 NF_HOOK include/linux/netfilter.h:289 [inline]
 ipv6_rcv+0x34b/0x3f0 net/ipv6/ip6_input.c:272
 __netif_receive_skb_one_core net/core/dev.c:4973 [inline]
 __netif_receive_skb net/core/dev.c:5083 [inline]
 process_backlog+0x756/0x10e0 net/core/dev.c:5923
 napi_poll net/core/dev.c:6346 [inline]
 net_rx_action+0x78b/0x1a60 net/core/dev.c:6412
 __do_softirq+0x53f/0x93a kernel/softirq.c:293
 do_softirq_own_stack+0x49/0x80 arch/x86/entry/entry_64.S:1039
 </IRQ>
 do_softirq kernel/softirq.c:338 [inline]
 __local_bh_enable_ip+0x16f/0x1a0 kernel/softirq.c:190
 local_bh_enable+0x36/0x40 include/linux/bottom_half.h:32
 rcu_read_unlock_bh include/linux/rcupdate.h:696 [inline]
 ip6_finish_output2+0x1d64/0x25f0 net/ipv6/ip6_output.c:121
 ip6_finish_output+0xae4/0xbc0 net/ipv6/ip6_output.c:154
 NF_HOOK_COND include/linux/netfilter.h:278 [inline]
 ip6_output+0x5ca/0x710 net/ipv6/ip6_output.c:171
 dst_output include/net/dst.h:444 [inline]
 ip6_local_out+0x164/0x1d0 net/ipv6/output_core.c:176
 ip6_send_skb+0xfa/0x390 net/ipv6/ip6_output.c:1727
 udp_v6_send_skb+0x1733/0x1d20 net/ipv6/udp.c:1169
 udpv6_sendmsg+0x424e/0x45d0 net/ipv6/udp.c:1466
 inet_sendmsg+0x54a/0x720 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg net/socket.c:631 [inline]
 ___sys_sendmsg+0xdb9/0x11b0 net/socket.c:2116
 __sys_sendmmsg+0x580/0xad0 net/socket.c:2211
 __do_sys_sendmmsg net/socket.c:2240 [inline]
 __se_sys_sendmmsg+0xbd/0xe0 net/socket.c:2237
 __x64_sys_sendmmsg+0x56/0x70 net/socket.c:2237
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x457ec9
Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4a5204fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000457ec9
RDX: 00000000040001ab RSI: 0000000020000240 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4a520506d4
R13: 00000000004c4ce5 R14: 00000000004d85d8 R15: 00000000ffffffff

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:205 [inline]
 kmsan_internal_poison_shadow+0x92/0x150 mm/kmsan/kmsan.c:159
 kmsan_kmalloc+0xa6/0x130 mm/kmsan/kmsan_hooks.c:176
 kmsan_slab_alloc+0xe/0x10 mm/kmsan/kmsan_hooks.c:185
 slab_post_alloc_hook mm/slab.h:446 [inline]
 slab_alloc_node mm/slub.c:2754 [inline]
 __kmalloc_node_track_caller+0xe9e/0xff0 mm/slub.c:4377
 __kmalloc_reserve net/core/skbuff.c:140 [inline]
 __alloc_skb+0x309/0xa20 net/core/skbuff.c:208
 alloc_skb include/linux/skbuff.h:1012 [inline]
 alloc_skb_with_frags+0x1c7/0xac0 net/core/skbuff.c:5288
 sock_alloc_send_pskb+0xafd/0x10a0 net/core/sock.c:2091
 sock_alloc_send_skb+0xca/0xe0 net/core/sock.c:2108
 __ip6_append_data+0x42ed/0x5dc0 net/ipv6/ip6_output.c:1443
 ip6_append_data+0x3c2/0x650 net/ipv6/ip6_output.c:1619
 icmp6_send+0x2f5c/0x3c40 net/ipv6/icmp.c:574
 icmpv6_send+0xe5/0x110 net/ipv6/ip6_icmp.c:43
 ip6_link_failure+0x5c/0x2c0 net/ipv6/route.c:2231
 dst_link_failure include/net/dst.h:427 [inline]
 vti_xmit net/ipv4/ip_vti.c:229 [inline]
 vti_tunnel_xmit+0xf3b/0x1ea0 net/ipv4/ip_vti.c:265
 __netdev_start_xmit include/linux/netdevice.h:4382 [inline]
 netdev_start_xmit include/linux/netdevice.h:4391 [inline]
 xmit_one net/core/dev.c:3278 [inline]
 dev_hard_start_xmit+0x604/0xc40 net/core/dev.c:3294
 __dev_queue_xmit+0x2e48/0x3b80 net/core/dev.c:3864
 dev_queue_xmit+0x4b/0x60 net/core/dev.c:3897
 neigh_direct_output+0x42/0x50 net/core/neighbour.c:1511
 neigh_output include/net/neighbour.h:508 [inline]
 ip6_finish_output2+0x1d4e/0x25f0 net/ipv6/ip6_output.c:120
 ip6_finish_output+0xae4/0xbc0 net/ipv6/ip6_output.c:154
 NF_HOOK_COND include/linux/netfilter.h:278 [inline]
 ip6_output+0x5ca/0x710 net/ipv6/ip6_output.c:171
 dst_output include/net/dst.h:444 [inline]
 ip6_local_out+0x164/0x1d0 net/ipv6/output_core.c:176
 ip6_send_skb+0xfa/0x390 net/ipv6/ip6_output.c:1727
 udp_v6_send_skb+0x1733/0x1d20 net/ipv6/udp.c:1169
 udpv6_sendmsg+0x424e/0x45d0 net/ipv6/udp.c:1466
 inet_sendmsg+0x54a/0x720 net/ipv4/af_inet.c:798
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg net/socket.c:631 [inline]
 ___sys_sendmsg+0xdb9/0x11b0 net/socket.c:2116
 __sys_sendmmsg+0x580/0xad0 net/socket.c:2211
 __do_sys_sendmmsg net/socket.c:2240 [inline]
 __se_sys_sendmmsg+0xbd/0xe0 net/socket.c:2237
 __x64_sys_sendmmsg+0x56/0x70 net/socket.c:2237
 do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
 entry_SYSCALL_64_after_hwframe+0x63/0xe7

Fixes: b8a51b38e4d4 ("fou, fou6: ICMP error handlers for FoU and GUE")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Stefano Brivio <sbrivio@redhat.com>
Cc: Sabrina Dubroca <sd@queasysnail.net>
---
 net/ipv4/fou.c  | 9 +++++++--
 net/ipv6/fou6.c | 9 +++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)
Stefano Brivio - Jan. 11, 2019, 2:15 p.m.
On Fri, 11 Jan 2019 04:55:52 -0800
Eric Dumazet <edumazet@google.com> wrote:

> Both gue_err() and gue6_err() incorrectly assume
> linear skbs. Fix them to use pskb_may_pull().

Thanks for fixing this! I stupidly didn't suspect we could get
non-linear skbs there. Just two things:

> +++ b/net/ipv4/fou.c
> @@ -1020,10 +1020,11 @@ static int gue_err(struct sk_buff *skb, u32 info)
>  {
>  	int transport_offset = skb_transport_offset(skb);
>  	struct guehdr *guehdr;
> -	size_t optlen;
> +	size_t len, optlen;
>  	int ret;
>  
> -	if (skb->len < sizeof(struct udphdr) + sizeof(struct guehdr))
> +	len = sizeof(struct udphdr) + sizeof(struct guehdr);
> +	if (!pskb_may_pull(skb, len))
>  		return -EINVAL;
>  
>  	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
> @@ -1058,6 +1059,10 @@ static int gue_err(struct sk_buff *skb, u32 info)
>  
>  	optlen = guehdr->hlen << 2;
>  
> +	if (!pskb_may_pull(skb, len + optlen)
                                             ^ ) missing

> +		return -EINVAL;
> +
> +	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
>  	if (validate_gue_flags(guehdr, optlen))
>  		return -EINVAL;
>  
> diff --git a/net/ipv6/fou6.c b/net/ipv6/fou6.c
> index 7da7bf3b7fe3953eeb60addfffd6687c4da582c4..320413af4890641e7199d7d7102e7d8c2794d557 100644
> --- a/net/ipv6/fou6.c
> +++ b/net/ipv6/fou6.c
> @@ -90,10 +90,11 @@ static int gue6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
>  {
>  	int transport_offset = skb_transport_offset(skb);
>  	struct guehdr *guehdr;
> -	size_t optlen;
> +	size_t len, optlen;
>  	int ret;
>  
> -	if (skb->len < sizeof(struct udphdr) + sizeof(struct guehdr))
> +	len = sizeof(struct udphdr) + sizeof(struct guehdr);
> +	if (!pskb_may_pull(skb, len))
>  		return -EINVAL;
>  
>  	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
> @@ -128,6 +129,10 @@ static int gue6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
>  
>  	optlen = guehdr->hlen << 2;
>  
> +	if (!pskb_may_pull(skb, len + optlen)
                                             ^ ) missing

> +		return -EINVAL;
> +
> +	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
>  	if (validate_gue_flags(guehdr, optlen))
>  		return -EINVAL;
>
Eric Dumazet - Jan. 11, 2019, 2:20 p.m.
On Fri, Jan 11, 2019 at 6:15 AM Stefano Brivio <sbrivio@redhat.com> wrote:
>
> On Fri, 11 Jan 2019 04:55:52 -0800
> Eric Dumazet <edumazet@google.com> wrote:
>
> > Both gue_err() and gue6_err() incorrectly assume
> > linear skbs. Fix them to use pskb_may_pull().
>
> Thanks for fixing this! I stupidly didn't suspect we could get
> non-linear skbs there. Just two things:


> > +     if (!pskb_may_pull(skb, len + optlen)
>                                              ^ ) missing


Interesting, I had no compile error there :/

I will send a V2
Eric Dumazet - Jan. 11, 2019, 2:23 p.m.
On Fri, Jan 11, 2019 at 6:20 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Fri, Jan 11, 2019 at 6:15 AM Stefano Brivio <sbrivio@redhat.com> wrote:
> >
> > On Fri, 11 Jan 2019 04:55:52 -0800
> > Eric Dumazet <edumazet@google.com> wrote:
> >
> > > Both gue_err() and gue6_err() incorrectly assume
> > > linear skbs. Fix them to use pskb_may_pull().
> >
> > Thanks for fixing this! I stupidly didn't suspect we could get
> > non-linear skbs there. Just two things:
>
>
> > > +     if (!pskb_may_pull(skb, len + optlen)
> >                                              ^ ) missing
>
>
> Interesting, I had no compile error there :/
>
> I will send a V2

Ah, CONFIG_NET_FOU_IP_TUNNELS was not set, of course.

Patch

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 632863541082230228da1e63927b9d5c72042350..02db3b0f263f7565fee53da3b8f2503ab2cd1dcb 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -1020,10 +1020,11 @@  static int gue_err(struct sk_buff *skb, u32 info)
 {
 	int transport_offset = skb_transport_offset(skb);
 	struct guehdr *guehdr;
-	size_t optlen;
+	size_t len, optlen;
 	int ret;
 
-	if (skb->len < sizeof(struct udphdr) + sizeof(struct guehdr))
+	len = sizeof(struct udphdr) + sizeof(struct guehdr);
+	if (!pskb_may_pull(skb, len))
 		return -EINVAL;
 
 	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
@@ -1058,6 +1059,10 @@  static int gue_err(struct sk_buff *skb, u32 info)
 
 	optlen = guehdr->hlen << 2;
 
+	if (!pskb_may_pull(skb, len + optlen)
+		return -EINVAL;
+
+	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
 	if (validate_gue_flags(guehdr, optlen))
 		return -EINVAL;
 
diff --git a/net/ipv6/fou6.c b/net/ipv6/fou6.c
index 7da7bf3b7fe3953eeb60addfffd6687c4da582c4..320413af4890641e7199d7d7102e7d8c2794d557 100644
--- a/net/ipv6/fou6.c
+++ b/net/ipv6/fou6.c
@@ -90,10 +90,11 @@  static int gue6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 {
 	int transport_offset = skb_transport_offset(skb);
 	struct guehdr *guehdr;
-	size_t optlen;
+	size_t len, optlen;
 	int ret;
 
-	if (skb->len < sizeof(struct udphdr) + sizeof(struct guehdr))
+	len = sizeof(struct udphdr) + sizeof(struct guehdr);
+	if (!pskb_may_pull(skb, len))
 		return -EINVAL;
 
 	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
@@ -128,6 +129,10 @@  static int gue6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 
 	optlen = guehdr->hlen << 2;
 
+	if (!pskb_may_pull(skb, len + optlen)
+		return -EINVAL;
+
+	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
 	if (validate_gue_flags(guehdr, optlen))
 		return -EINVAL;