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* [PATCH v2] locking/lockdep: Fix buffer overrun problem in stack_trace[]
@ 2019-12-20 13:51 Waiman Long
  2019-12-20 15:23 ` Bart Van Assche
  2019-12-25 10:39 ` [tip: locking/urgent] " tip-bot2 for Waiman Long
  0 siblings, 2 replies; 3+ messages in thread
From: Waiman Long @ 2019-12-20 13:51 UTC (permalink / raw)
  To: Peter Zijlstra, Ingo Molnar, Will Deacon
  Cc: linux-kernel, Bart Van Assche, Waiman Long

If the lockdep code is really running out of the stack_trace entries,
it is likely that buffer overrun can happen and the data immediately
after stack_trace[] will be corrupted.

If there is less than LOCK_TRACE_SIZE_IN_LONGS entries left before
the call to save_trace(), the max_entries computation will leave it
with a very large positive number because of its unsigned nature. The
subsequent call to stack_trace_save() will then corrupt the data after
stack_trace[]. Fix that by changing max_entries to a signed integer
and check for negative value before calling stack_trace_save().

Fixes: 12593b7467f9 ("locking/lockdep: Reduce space occupied by stack traces")
Signed-off-by: Waiman Long <longman@redhat.com>
---
 kernel/locking/lockdep.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 32282e7112d3..32406ef0d6a2 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -482,7 +482,7 @@ static struct lock_trace *save_trace(void)
 	struct lock_trace *trace, *t2;
 	struct hlist_head *hash_head;
 	u32 hash;
-	unsigned int max_entries;
+	int max_entries;
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
 	BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
@@ -490,10 +490,8 @@ static struct lock_trace *save_trace(void)
 	trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
 	max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
 		LOCK_TRACE_SIZE_IN_LONGS;
-	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
-	if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES -
-	    LOCK_TRACE_SIZE_IN_LONGS - 1) {
+	if (max_entries <= 0) {
 		if (!debug_locks_off_graph_unlock())
 			return NULL;
 
@@ -502,6 +500,7 @@ static struct lock_trace *save_trace(void)
 
 		return NULL;
 	}
+	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
 	hash = jhash(trace->entries, trace->nr_entries *
 		     sizeof(trace->entries[0]), 0);
-- 
2.18.1


^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH v2] locking/lockdep: Fix buffer overrun problem in stack_trace[]
  2019-12-20 13:51 [PATCH v2] locking/lockdep: Fix buffer overrun problem in stack_trace[] Waiman Long
@ 2019-12-20 15:23 ` Bart Van Assche
  2019-12-25 10:39 ` [tip: locking/urgent] " tip-bot2 for Waiman Long
  1 sibling, 0 replies; 3+ messages in thread
From: Bart Van Assche @ 2019-12-20 15:23 UTC (permalink / raw)
  To: Waiman Long, Peter Zijlstra, Ingo Molnar, Will Deacon; +Cc: linux-kernel

On 2019-12-20 05:51, Waiman Long wrote:
> If the lockdep code is really running out of the stack_trace entries,
> it is likely that buffer overrun can happen and the data immediately
> after stack_trace[] will be corrupted.
> 
> If there is less than LOCK_TRACE_SIZE_IN_LONGS entries left before
> the call to save_trace(), the max_entries computation will leave it
> with a very large positive number because of its unsigned nature. The
> subsequent call to stack_trace_save() will then corrupt the data after
> stack_trace[]. Fix that by changing max_entries to a signed integer
> and check for negative value before calling stack_trace_save().

Reviewed-by: Bart Van Assche <bvanassche@acm.org>

^ permalink raw reply	[flat|nested] 3+ messages in thread
* [tip: locking/urgent] locking/lockdep: Fix buffer overrun problem in stack_trace[]
  2019-12-20 13:51 [PATCH v2] locking/lockdep: Fix buffer overrun problem in stack_trace[] Waiman Long
  2019-12-20 15:23 ` Bart Van Assche
@ 2019-12-25 10:39 ` tip-bot2 for Waiman Long
  1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Waiman Long @ 2019-12-25 10:39 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Waiman Long, Peter Zijlstra (Intel),
	Bart Van Assche, Linus Torvalds, Thomas Gleixner, Ingo Molnar,
	x86, LKML

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     d91f3057263ceb691ef527e71b41a56b17f6c869
Gitweb:        https://git.kernel.org/tip/d91f3057263ceb691ef527e71b41a56b17f6c869
Author:        Waiman Long <longman@redhat.com>
AuthorDate:    Fri, 20 Dec 2019 08:51:28 -05:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 25 Dec 2019 10:42:32 +01:00

locking/lockdep: Fix buffer overrun problem in stack_trace[]

If the lockdep code is really running out of the stack_trace entries,
it is likely that buffer overrun can happen and the data immediately
after stack_trace[] will be corrupted.

If there is less than LOCK_TRACE_SIZE_IN_LONGS entries left before
the call to save_trace(), the max_entries computation will leave it
with a very large positive number because of its unsigned nature. The
subsequent call to stack_trace_save() will then corrupt the data after
stack_trace[]. Fix that by changing max_entries to a signed integer
and check for negative value before calling stack_trace_save().

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 12593b7467f9 ("locking/lockdep: Reduce space occupied by stack traces")
Link: https://lkml.kernel.org/r/20191220135128.14876-1-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/locking/lockdep.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 32282e7..32406ef 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -482,7 +482,7 @@ static struct lock_trace *save_trace(void)
 	struct lock_trace *trace, *t2;
 	struct hlist_head *hash_head;
 	u32 hash;
-	unsigned int max_entries;
+	int max_entries;
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
 	BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
@@ -490,10 +490,8 @@ static struct lock_trace *save_trace(void)
 	trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
 	max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
 		LOCK_TRACE_SIZE_IN_LONGS;
-	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
-	if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES -
-	    LOCK_TRACE_SIZE_IN_LONGS - 1) {
+	if (max_entries <= 0) {
 		if (!debug_locks_off_graph_unlock())
 			return NULL;
 
@@ -502,6 +500,7 @@ static struct lock_trace *save_trace(void)
 
 		return NULL;
 	}
+	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
 	hash = jhash(trace->entries, trace->nr_entries *
 		     sizeof(trace->entries[0]), 0);

^ permalink raw reply related	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-12-25 10:39 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2019-12-20 13:51 [PATCH v2] locking/lockdep: Fix buffer overrun problem in stack_trace[] Waiman Long
2019-12-20 15:23 ` Bart Van Assche
2019-12-25 10:39 ` [tip: locking/urgent] " tip-bot2 for Waiman Long

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