From: Waiman Long longman@redhat.com
[ Upstream commit d91f3057263ceb691ef527e71b41a56b17f6c869 ]
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 Signed-off-by: Sasha Levin sashal@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 233459c03b5ae..35d3b6925b1ee 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);