linux-kernel - [PATCH 2/5] mm, slub: fix mismatch between reconstructed freelist depth and cnt

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Message-ID: <20210916123920.48704-3-linmiaohe@huawei.com>
Date:   Thu, 16 Sep 2021 20:39:17 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <cl@...ux.com>, <penberg@...nel.org>,
        <rientjes@...gle.com>, <iamjoonsoo.kim@....com>, <vbabka@...e.cz>
CC:     <gregkh@...uxfoundation.org>, <faiyazm@...eaurora.org>,
        <andreyknvl@...il.com>, <ryabinin.a.a@...il.com>,
        <thgarnie@...gle.com>, <keescook@...omium.org>,
        <bharata@...ux.ibm.com>, <guro@...com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH 2/5] mm, slub: fix mismatch between reconstructed freelist depth and cnt

If object's reuse is delayed, it will be excluded from the reconstructed
freelist. But we forgot to adjust the cnt accordingly. So there will be
a mismatch between reconstructed freelist depth and cnt. This will lead
to free_debug_processing() complain about freelist count or a incorrect
slub inuse count.

Fixes: c3895391df38 ("kasan, slub: fix handling of kasan_slab_free hook")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/slub.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index ed160b6c54f8..a56a6423d4e8 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1701,7 +1701,8 @@ static __always_inline bool slab_free_hook(struct kmem_cache *s,
 }
 
 static inline bool slab_free_freelist_hook(struct kmem_cache *s,
-					   void **head, void **tail)
+					   void **head, void **tail,
+					   int *cnt)
 {
 
 	void *object;
@@ -1728,6 +1729,12 @@ static inline bool slab_free_freelist_hook(struct kmem_cache *s,
 			*head = object;
 			if (!*tail)
 				*tail = object;
+		} else {
+			/*
+			 * Adjust the reconstructed freelist depth
+			 * accordingly if object's reuse is delayed.
+			 */
+			--(*cnt);
 		}
 	} while (object != old_tail);
 
@@ -3480,7 +3487,7 @@ static __always_inline void slab_free(struct kmem_cache *s, struct page *page,
 	 * With KASAN enabled slab_free_freelist_hook modifies the freelist
 	 * to remove objects, whose reuse must be delayed.
 	 */
-	if (slab_free_freelist_hook(s, &head, &tail))
+	if (slab_free_freelist_hook(s, &head, &tail, &cnt))
 		do_slab_free(s, page, head, tail, cnt, addr);
 }
 
-- 
2.23.0