From: Matthew Dawson <matthew@mjdsystems.ca>
Date: Fri, 11 Mar 2016 21:08:07 +0000 (-0800)
Subject: mm/mempool: avoid KASAN marking mempool poison checks as use-after-free
X-Git-Tag: v4.14-rc1~3695
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=7640131032db9118a78af715ac77ba2debeeb17c;p=platform%2Fkernel%2Flinux-rpi.git

mm/mempool: avoid KASAN marking mempool poison checks as use-after-free

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

diff --git a/mm/mempool.c b/mm/mempool.c
index 004d42b..7924f4f 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;
 }