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Subject[PATCH] lib/stackdepot: Fix global out-of-bounds in stackdepot
Date
If the depot_index = STACK_ALLOC_MAX_SLABS - 2, then it will cause
array out-of-bounds access, so that we should modify the detection
to avoid this array out-of-bounds bug.

Consider following call flow sequence:

stack_depot_save()
depot_alloc_stack()
if (unlikely(depot_index + 1 >= STACK_ALLOC_MAX_SLABS)) //pass
depot_index++ //depot_index = STACK_ALLOC_MAX_SLABS - 1

stack_depot_save()
init_stack_slab()
stack_slabs[depot_index + 1] //here get global out-of-bounds

Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
---
lib/stackdepot.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index ed717dd08ff3..7e8a15e41600 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -106,7 +106,7 @@ static struct stack_record *depot_alloc_stack(unsigned long *entries, int size,
required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN);

if (unlikely(depot_offset + required_size > STACK_ALLOC_SIZE)) {
- if (unlikely(depot_index + 1 >= STACK_ALLOC_MAX_SLABS)) {
+ if (unlikely(depot_index + 2 >= STACK_ALLOC_MAX_SLABS)) {
WARN_ONCE(1, "Stack depot reached limit capacity");
return NULL;
}
--
2.18.0
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