Patchwork soc: qcom: rpmh: Avoid accessing freed memory from batch API

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Submitter Lina Iyer
Date Jan. 8, 2019, 5:49 p.m.
Message ID <20190108174938.GA22547@codeaurora.org>
Download mbox | patch
Permalink /patch/695121/
State New
Headers show

Comments

Lina Iyer - Jan. 8, 2019, 5:49 p.m.
On Thu, Jan 03 2019 at 10:47 -0700, Stephen Boyd wrote:
>Using the batch API from the interconnect driver sometimes leads to a
>KASAN error due to an access to freed memory. This is easier to trigger
>with threadirqs on the kernel commandline.
>
> BUG: KASAN: use-after-free in rpmh_tx_done+0x114/0x12c
> Read of size 1 at addr fffffff51414ad84 by task irq/110-apps_rs/57
>
> CPU: 0 PID: 57 Comm: irq/110-apps_rs Tainted: G        W         4.19.10 #72
> Call trace:
>  dump_backtrace+0x0/0x2f8
>  show_stack+0x20/0x2c
>  __dump_stack+0x20/0x28
>  dump_stack+0xcc/0x10c
>  print_address_description+0x74/0x240
>  kasan_report+0x250/0x26c
>  __asan_report_load1_noabort+0x20/0x2c
>  rpmh_tx_done+0x114/0x12c
>  tcs_tx_done+0x450/0x768
>  irq_forced_thread_fn+0x58/0x9c
>  irq_thread+0x120/0x1dc
>  kthread+0x248/0x260
>  ret_from_fork+0x10/0x18
>
> Allocated by task 385:
>  kasan_kmalloc+0xac/0x148
>  __kmalloc+0x170/0x1e4
>  rpmh_write_batch+0x174/0x540
>  qcom_icc_set+0x8dc/0x9ac
>  icc_set+0x288/0x2e8
>  a6xx_gmu_stop+0x320/0x3c0
>  a6xx_pm_suspend+0x108/0x124
>  adreno_suspend+0x50/0x60
>  pm_generic_runtime_suspend+0x60/0x78
>  __rpm_callback+0x214/0x32c
>  rpm_callback+0x54/0x184
>  rpm_suspend+0x3f8/0xa90
>  pm_runtime_work+0xb4/0x178
>  process_one_work+0x544/0xbc0
>  worker_thread+0x514/0x7d0
>  kthread+0x248/0x260
>  ret_from_fork+0x10/0x18
>
> Freed by task 385:
>  __kasan_slab_free+0x12c/0x1e0
>  kasan_slab_free+0x10/0x1c
>  kfree+0x134/0x588
>  rpmh_write_batch+0x49c/0x540
>  qcom_icc_set+0x8dc/0x9ac
>  icc_set+0x288/0x2e8
>  a6xx_gmu_stop+0x320/0x3c0
>  a6xx_pm_suspend+0x108/0x124
>  adreno_suspend+0x50/0x60
> cr50_spi spi5.0: SPI transfer timed out
>  pm_generic_runtime_suspend+0x60/0x78
>  __rpm_callback+0x214/0x32c
>  rpm_callback+0x54/0x184
>  rpm_suspend+0x3f8/0xa90
>  pm_runtime_work+0xb4/0x178
>  process_one_work+0x544/0xbc0
>  worker_thread+0x514/0x7d0
>  kthread+0x248/0x260
>  ret_from_fork+0x10/0x18
>
> The buggy address belongs to the object at fffffff51414ac80
>  which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 260 bytes inside of
>  512-byte region [fffffff51414ac80, fffffff51414ae80)
> The buggy address belongs to the page:
> page:ffffffbfd4505200 count:1 mapcount:0 mapping:fffffff51e00c680 index:0x0 compound_mapcount: 0
> flags: 0x4000000000008100(slab|head)
> raw: 4000000000008100 ffffffbfd4529008 ffffffbfd44f9208 fffffff51e00c680
> raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  fffffff51414ac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  fffffff51414ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >fffffff51414ad80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                    ^
>  fffffff51414ae00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  fffffff51414ae80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>
>The batch API sets the same completion for each rpmh message that's sent
>and then loops through all the messages and waits for that single
>completion declared on the stack to be completed before returning from
>the function and freeing the message structures. Unfortunately, some
>messages may still be in process and 'stuck' in the TCS. At some later
>point, the tcs_tx_done() interrupt will run and try to process messages
>that have already been freed at the end of rpmh_write_batch(). This will
>in turn access the 'needs_free' member of the rpmh_request structure and
>cause KASAN to complain.
>
Raju and I were discussing this solution and we think the issue may be
because of a race condition between the thread calling the completion
and the thread waiting for completion. Completion releases the waiting
thread and then we try to read rpm_msg->needs_free after that. But, if
we could read in the rpm_msg->needs_free before calling completion, we
would not see the problem. How about this instead?



>Let's fix this by allocating a chunk of completions for each message and
>waiting for all of them to be completed before returning from the batch
>API. Alternatively, we could wait for the last message in the batch, but
>that may be a more complicated change because it looks like
>tcs_tx_done() just iterates through the indices of the queue and
>completes each message instead of tracking the last inserted message and
>completing that first.
>
>Cc: Lina Iyer <ilina@codeaurora.org>
>Cc: "Raju P.L.S.S.S.N" <rplsssn@codeaurora.org>
>Cc: Matthias Kaehlcke <mka@chromium.org>
>Cc: Evan Green <evgreen@chromium.org>
>Fixes: c8790cb6da58 ("drivers: qcom: rpmh: add support for batch RPMH request")
>Signed-off-by: Stephen Boyd <swboyd@chromium.org>
>---
> drivers/soc/qcom/rpmh.c | 25 +++++++++++++++++--------
> 1 file changed, 17 insertions(+), 8 deletions(-)
>
>diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
>index c7beb6841289..3b3e8b0b2d95 100644
>--- a/drivers/soc/qcom/rpmh.c
>+++ b/drivers/soc/qcom/rpmh.c
>@@ -348,11 +348,12 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
> {
> 	struct batch_cache_req *req;
> 	struct rpmh_request *rpm_msgs;
>-	DECLARE_COMPLETION_ONSTACK(compl);
>+	struct completion *compls;
> 	struct rpmh_ctrlr *ctrlr = get_rpmh_ctrlr(dev);
> 	unsigned long time_left;
> 	int count = 0;
> 	int ret, i, j;
>+	void *ptr;
>
> 	if (!cmd || !n)
> 		return -EINVAL;
>@@ -362,10 +363,15 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
> 	if (!count)
> 		return -EINVAL;
>
>-	req = kzalloc(sizeof(*req) + count * sizeof(req->rpm_msgs[0]),
>+	ptr = kzalloc(sizeof(*req) +
>+		      count * (sizeof(req->rpm_msgs[0]) + sizeof(*compls)),
> 		      GFP_ATOMIC);
>-	if (!req)
>+	if (!ptr)
> 		return -ENOMEM;
>+
>+	req = ptr;
>+	compls = ptr + sizeof(*req) + count * sizeof(*rpm_msgs);
>+
> 	req->count = count;
> 	rpm_msgs = req->rpm_msgs;
>
>@@ -380,7 +386,10 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
> 	}
>
> 	for (i = 0; i < count; i++) {
>-		rpm_msgs[i].completion = &compl;
>+		struct completion *compl = &compls[i];
>+
>+		init_completion(compl);
>+		rpm_msgs[i].completion = compl;
> 		ret = rpmh_rsc_send_data(ctrlr_to_drv(ctrlr), &rpm_msgs[i].msg);
> 		if (ret) {
> 			pr_err("Error(%d) sending RPMH message addr=%#x\n",
>@@ -393,12 +402,12 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
>
> 	time_left = RPMH_TIMEOUT_MS;
> 	for (i = 0; i < count; i++) {
>-		time_left = wait_for_completion_timeout(&compl, time_left);
>+		time_left = wait_for_completion_timeout(&compls[i], time_left);
> 		if (!time_left) {
> 			/*
> 			 * Better hope they never finish because they'll signal
>-			 * the completion on our stack and that's bad once
>-			 * we've returned from the function.
>+			 * the completion that we're going to free once
>+			 * we've returned from this function.
> 			 */
> 			WARN_ON(1);
> 			ret = -ETIMEDOUT;
>@@ -407,7 +416,7 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
> 	}
>
> exit:
>-	kfree(req);
>+	kfree(ptr);
>
> 	return ret;
> }
>-- 
>Sent by a computer through tubes
>
Evan Green - Jan. 8, 2019, 6:30 p.m.
On Tue, Jan 8, 2019 at 9:49 AM Lina Iyer <ilina@codeaurora.org> wrote:
>
> On Thu, Jan 03 2019 at 10:47 -0700, Stephen Boyd wrote:
> >Using the batch API from the interconnect driver sometimes leads to a
> >KASAN error due to an access to freed memory. This is easier to trigger
> >with threadirqs on the kernel commandline.
> >
> > BUG: KASAN: use-after-free in rpmh_tx_done+0x114/0x12c
> > Read of size 1 at addr fffffff51414ad84 by task irq/110-apps_rs/57
> >
> > CPU: 0 PID: 57 Comm: irq/110-apps_rs Tainted: G        W         4.19.10 #72
> > Call trace:
> >  dump_backtrace+0x0/0x2f8
> >  show_stack+0x20/0x2c
> >  __dump_stack+0x20/0x28
> >  dump_stack+0xcc/0x10c
> >  print_address_description+0x74/0x240
> >  kasan_report+0x250/0x26c
> >  __asan_report_load1_noabort+0x20/0x2c
> >  rpmh_tx_done+0x114/0x12c
> >  tcs_tx_done+0x450/0x768
> >  irq_forced_thread_fn+0x58/0x9c
> >  irq_thread+0x120/0x1dc
> >  kthread+0x248/0x260
> >  ret_from_fork+0x10/0x18
> >
> > Allocated by task 385:
> >  kasan_kmalloc+0xac/0x148
> >  __kmalloc+0x170/0x1e4
> >  rpmh_write_batch+0x174/0x540
> >  qcom_icc_set+0x8dc/0x9ac
> >  icc_set+0x288/0x2e8
> >  a6xx_gmu_stop+0x320/0x3c0
> >  a6xx_pm_suspend+0x108/0x124
> >  adreno_suspend+0x50/0x60
> >  pm_generic_runtime_suspend+0x60/0x78
> >  __rpm_callback+0x214/0x32c
> >  rpm_callback+0x54/0x184
> >  rpm_suspend+0x3f8/0xa90
> >  pm_runtime_work+0xb4/0x178
> >  process_one_work+0x544/0xbc0
> >  worker_thread+0x514/0x7d0
> >  kthread+0x248/0x260
> >  ret_from_fork+0x10/0x18
> >
> > Freed by task 385:
> >  __kasan_slab_free+0x12c/0x1e0
> >  kasan_slab_free+0x10/0x1c
> >  kfree+0x134/0x588
> >  rpmh_write_batch+0x49c/0x540
> >  qcom_icc_set+0x8dc/0x9ac
> >  icc_set+0x288/0x2e8
> >  a6xx_gmu_stop+0x320/0x3c0
> >  a6xx_pm_suspend+0x108/0x124
> >  adreno_suspend+0x50/0x60
> > cr50_spi spi5.0: SPI transfer timed out
> >  pm_generic_runtime_suspend+0x60/0x78
> >  __rpm_callback+0x214/0x32c
> >  rpm_callback+0x54/0x184
> >  rpm_suspend+0x3f8/0xa90
> >  pm_runtime_work+0xb4/0x178
> >  process_one_work+0x544/0xbc0
> >  worker_thread+0x514/0x7d0
> >  kthread+0x248/0x260
> >  ret_from_fork+0x10/0x18
> >
> > The buggy address belongs to the object at fffffff51414ac80
> >  which belongs to the cache kmalloc-512 of size 512
> > The buggy address is located 260 bytes inside of
> >  512-byte region [fffffff51414ac80, fffffff51414ae80)
> > The buggy address belongs to the page:
> > page:ffffffbfd4505200 count:1 mapcount:0 mapping:fffffff51e00c680 index:0x0 compound_mapcount: 0
> > flags: 0x4000000000008100(slab|head)
> > raw: 4000000000008100 ffffffbfd4529008 ffffffbfd44f9208 fffffff51e00c680
> > raw: 0000000000000000 0000000000200020 00000001ffffffff 0000000000000000
> > page dumped because: kasan: bad access detected
> >
> > Memory state around the buggy address:
> >  fffffff51414ac80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  fffffff51414ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >fffffff51414ad80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >                    ^
> >  fffffff51414ae00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >  fffffff51414ae80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >
> >The batch API sets the same completion for each rpmh message that's sent
> >and then loops through all the messages and waits for that single
> >completion declared on the stack to be completed before returning from
> >the function and freeing the message structures. Unfortunately, some
> >messages may still be in process and 'stuck' in the TCS. At some later
> >point, the tcs_tx_done() interrupt will run and try to process messages
> >that have already been freed at the end of rpmh_write_batch(). This will
> >in turn access the 'needs_free' member of the rpmh_request structure and
> >cause KASAN to complain.
> >
> Raju and I were discussing this solution and we think the issue may be
> because of a race condition between the thread calling the completion
> and the thread waiting for completion. Completion releases the waiting
> thread and then we try to read rpm_msg->needs_free after that. But, if
> we could read in the rpm_msg->needs_free before calling completion, we
> would not see the problem. How about this instead?
>
> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> index c7beb6841289..0303a2971d4a 100644
> --- a/drivers/soc/qcom/rpmh.c
> +++ b/drivers/soc/qcom/rpmh.c
> @@ -80,6 +80,7 @@ void rpmh_tx_done(const struct tcs_request *msg, int r)
>         struct rpmh_request *rpm_msg = container_of(msg, struct rpmh_request,
>                                                     msg);
>         struct completion *compl = rpm_msg->completion;
> +       bool free = rpm_msg->needs_free;
>
>         rpm_msg->err = r;
>
> @@ -94,7 +95,7 @@ void rpmh_tx_done(const struct tcs_request *msg, int r)
>         complete(compl);
>
>  exit:
> -       if (rpm_msg->needs_free)
> +       if (free)
>                 kfree(rpm_msg);
>  }
>

Hi Lina,
I think that's a worthy fix, too, and is needed to solve the issue you describe.

But I think Stephen's fix is still needed. In the rpmh_write_batch
scenario, we queue N things into rpmh, but set the same completion for
all of them. If only the first one completes but not the others, then
the loop in rpmh_write_batch will call wait_for_completion_timeout N
times on the same completion, and then goes on to free all N requests,
even though only the first one is actually done and out of the system
(well, almost out of the system, with the bug you noticed above).

We considered having just one completion on the last transfer, but
then if there's an error part way through you have no way of waiting
on the transfers that did get submitted. So I think N completions are
needed.
-Evan
Stephen Boyd - Jan. 8, 2019, 6:52 p.m.
Quoting Evan Green (2019-01-08 10:30:04)
> On Tue, Jan 8, 2019 at 9:49 AM Lina Iyer <ilina@codeaurora.org> wrote:
> >
> > diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> > index c7beb6841289..0303a2971d4a 100644
> > --- a/drivers/soc/qcom/rpmh.c
> > +++ b/drivers/soc/qcom/rpmh.c
> > @@ -80,6 +80,7 @@ void rpmh_tx_done(const struct tcs_request *msg, int r)
> >         struct rpmh_request *rpm_msg = container_of(msg, struct rpmh_request,
> >                                                     msg);
> >         struct completion *compl = rpm_msg->completion;
> > +       bool free = rpm_msg->needs_free;
> >
> >         rpm_msg->err = r;
> >
> > @@ -94,7 +95,7 @@ void rpmh_tx_done(const struct tcs_request *msg, int r)
> >         complete(compl);
> >
> >  exit:
> > -       if (rpm_msg->needs_free)
> > +       if (free)
> >                 kfree(rpm_msg);
> >  }
> >
> 
> Hi Lina,
> I think that's a worthy fix, too, and is needed to solve the issue you describe.

Looks like we need both fixes so I can combine them together.

> 
> But I think Stephen's fix is still needed. In the rpmh_write_batch
> scenario, we queue N things into rpmh, but set the same completion for
> all of them. If only the first one completes but not the others, then
> the loop in rpmh_write_batch will call wait_for_completion_timeout N
> times on the same completion, and then goes on to free all N requests,
> even though only the first one is actually done and out of the system
> (well, almost out of the system, with the bug you noticed above).

This code looks an awful lot like kref_put() with a release function
that's a kfree() of the rpm message. Would that simplify the code
somewhat if we made a refcounter (that probably only counted up to 2)
and then properly refcounted the messages? We would have to allocate a
bunch of messages for the batch writing API, but I'm not sure that's a
big deal either.

> 
> We considered having just one completion on the last transfer, but
> then if there's an error part way through you have no way of waiting
> on the transfers that did get submitted. So I think N completions are
> needed.

For that, I'd like to make the batch API know more about the TCS it's
filling so it can know how to unwind the state if something fails. From
what I can tell this function is implemented at the wrong abstraction
level. It should be a lower level function so it can manage the queue
and push multiple messages through.

Patch

diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
index c7beb6841289..0303a2971d4a 100644
--- a/drivers/soc/qcom/rpmh.c
+++ b/drivers/soc/qcom/rpmh.c
@@ -80,6 +80,7 @@  void rpmh_tx_done(const struct tcs_request *msg, int r)
        struct rpmh_request *rpm_msg = container_of(msg, struct rpmh_request,
                                                    msg);
        struct completion *compl = rpm_msg->completion;
+       bool free = rpm_msg->needs_free;

        rpm_msg->err = r;

@@ -94,7 +95,7 @@  void rpmh_tx_done(const struct tcs_request *msg, int r)
        complete(compl);

 exit:
-       if (rpm_msg->needs_free)
+       if (free)
                kfree(rpm_msg);
 }