linux-kernel - [PATCH mm] kfence, slab: fix cache_alloc_debugcheck

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Message-Id: <20210304205256.2162309-1-elver@google.com>
Date:   Thu,  4 Mar 2021 21:52:56 +0100
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, akpm@...ux-foundation.org
Cc:     glider@...gle.com, dvyukov@...gle.com, andreyknvl@...gle.com,
        jannh@...gle.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kasan-dev@...glegroups.com
Subject: [PATCH mm] kfence, slab: fix cache_alloc_debugcheck_after() for bulk allocations

cache_alloc_debugcheck_after() performs checks on an object, including
adjusting the returned pointer. None of this should apply to KFENCE
objects. While for non-bulk allocations, the checks are skipped when we
allocate via KFENCE, for bulk allocations cache_alloc_debugcheck_after()
is called via cache_alloc_debugcheck_after_bulk().

Fix it by skipping cache_alloc_debugcheck_after() for KFENCE objects.

Signed-off-by: Marco Elver <elver@...gle.com>
---
 mm/slab.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slab.c b/mm/slab.c
index 51fd424e0d6d..ae651bf540b7 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2992,7 +2992,7 @@ static void *cache_alloc_debugcheck_after(struct kmem_cache *cachep,
 				gfp_t flags, void *objp, unsigned long caller)
 {
 	WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));
-	if (!objp)
+	if (!objp || is_kfence_address(objp))
 		return objp;
 	if (cachep->flags & SLAB_POISON) {
 		check_poison_obj(cachep, objp);
-- 
2.30.1.766.gb4fecdf3b7-goog