Messages in this thread Patch in this message | | | From | Waiman Long <> | Subject | [PATCH] locking/lockdep: Fix potential buffer overrun problem in stack_trace[] | Date | Thu, 19 Dec 2019 13:28:12 -0500 |
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If the lockdep code is really running out of the stack_trace entries, there is a possiblity that buffer overrun can happen and corrupt the data immediately after stack_trace[].
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..56e260a7582f 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
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