linux-kernel - [PATCH] mm,slub: do not call do_slab

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Message-ID: <20240729141928.4545a093@imladris.surriel.com>
Date: Mon, 29 Jul 2024 14:19:28 -0400
From: Rik van Riel <riel@...riel.com>
To: clm@...a.com
Cc: Pekka Enberg <penberg@...nel.org>, Christoph Lameter <cl@...ux.com>,
 Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka
 <vbabka@...e.cz>, kernel-team@...a.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Joonsoo Kim <iamjoonsoo.kim@....com>, David
 Rientjes <rientjes@...gle.com>
Subject: [PATCH] mm,slub: do not call do_slab_free for kfence object

In 782f8906f805 the freeing of kfence objects was moved from deep
inside do_free_slab to the wrapper functions outside. This is a nice
change, but unfortunately it missed one spot in __kmem_cache_free_bulk.

This results in a crash like this:

BUG skbuff_head_cache (Tainted: G S  B       E     ): Padding overwritten. 0xffff88907fea0f00-0xffff88907fea0fff @offset=3840

slab_err (mm/slub.c:1129)
free_to_partial_list (mm/slub.c:? mm/slub.c:4036)
slab_pad_check (mm/slub.c:864 mm/slub.c:1290)
check_slab (mm/slub.c:?)
free_to_partial_list (mm/slub.c:3171 mm/slub.c:4036)
kmem_cache_alloc_bulk (mm/slub.c:? mm/slub.c:4495 mm/slub.c:4586 mm/slub.c:4635)
napi_build_skb (net/core/skbuff.c:348 net/core/skbuff.c:527 net/core/skbuff.c:549)

All the other callers to do_free_slab appear to be ok.

Add a kfence_free check in __kmem_cache_free_bulk to avoid the crash.

Reported-by: Chris Mason <clm@...a.com>
Fixes: 782f8906f805 ("mm/slub: free KFENCE objects in slab_free_hook()")
Cc: stable@...nel.org
Signed-off-by: Rik van Riel <riel@...riel.com>
---
 mm/slub.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/slub.c b/mm/slub.c
index 3520acaf9afa..c9d8a2497fd6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4690,6 +4690,9 @@ static void __kmem_cache_free_bulk(struct kmem_cache *s, size_t size, void **p)
 		if (!df.slab)
 			continue;
 
+		if (kfence_free(df.freelist))
+			continue;
+
 		do_slab_free(df.s, df.slab, df.freelist, df.tail, df.cnt,
 			     _RET_IP_);
 	} while (likely(size));
-- 
2.45.2