[Devel] [PATCH rh7 05/39] mm/mempool: avoid KASAN marking mempool poison checks as use-after-free

[Andrey Ryabinin]

From: Matthew Dawson <matthew at mjdsystems.ca>

When removing an element from the mempool, mark it as unpoisoned in KASAN
before verifying its contents for SLUB/SLAB debugging.  Otherwise KASAN
will flag the reads checking the element use-after-free writes as
use-after-free reads.

Signed-off-by: Matthew Dawson <matthew at mjdsystems.ca>
Acked-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>

https://jira.sw.ru/browse/PSBM-69081
(cherry picked from commit 7640131032db9118a78af715ac77ba2debeeb17c)
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 mm/mempool.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mempool.c b/mm/mempool.c
index d9fa60d6f098..791ec8a148b4 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -135,8 +135,8 @@ static void *remove_element(mempool_t *pool)
 	void *element = pool->elements[--pool->curr_nr];
 
 	BUG_ON(pool->curr_nr < 0);
-	check_element(pool, element);
 	kasan_unpoison_element(pool, element);
+	check_element(pool, element);
 	return element;
 }
 
-- 
2.13.5