linux-kernel - [PATCH] mm/slab: Perform init_on

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Date:   Thu, 10 Dec 2020 21:37:29 +0300
From:   Alexander Popov <alex.popov@...ux.com>
To:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com,
        Alexander Popov <alex.popov@...ux.com>
Cc:     notify@...nel.org
Subject: [PATCH] mm/slab: Perform init_on_free earlier

Currently in CONFIG_SLAB init_on_free happens too late, and heap
objects go to the heap quarantine not being erased.

Lets move init_on_free clearing before calling kasan_slab_free().
In that case heap quarantine will store erased objects, similarly
to CONFIG_SLUB=y behavior.

Signed-off-by: Alexander Popov <alex.popov@...ux.com>
Reviewed-by: Alexander Potapenko <glider@...gle.com>
---
 mm/slab.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index b1113561b98b..344a101e37e0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3416,6 +3416,9 @@ static void cache_flusharray(struct kmem_cache *cachep, struct array_cache *ac)
 static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp,
 					 unsigned long caller)
 {
+	if (unlikely(slab_want_init_on_free(cachep)))
+		memset(objp, 0, cachep->object_size);
+
 	/* Put the object into the quarantine, don't touch it for now. */
 	if (kasan_slab_free(cachep, objp, _RET_IP_))
 		return;
@@ -3434,8 +3437,6 @@ void ___cache_free(struct kmem_cache *cachep, void *objp,
 	struct array_cache *ac = cpu_cache_get(cachep);
 
 	check_irq_off();
-	if (unlikely(slab_want_init_on_free(cachep)))
-		memset(objp, 0, cachep->object_size);
 	kmemleak_free_recursive(objp, cachep->flags);
 	objp = cache_free_debugcheck(cachep, objp, caller);
 	memcg_slab_free_hook(cachep, &objp, 1);
-- 
2.26.2