linux-kernel - [PATCH] slub: Fix a crash during slabinfo -v

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Date:	Wed, 1 Dec 2010 20:04:20 +0200 (EET)
From:	Tero Roponen <tero.roponen@...il.com>
To:	linux-kernel@...r.kernel.org
cc:	David Rientjes <rientjes@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>
Subject: [PATCH] slub: Fix a crash during slabinfo -v

Commit f7cb1933621bce66a77f690776a16fe3ebbc4d58 ("SLUB: Pass active
and inactive redzone flags instead of boolean to debug functions")
missed two instances of check_object(). This caused a lot of warnings
during 'slabinfo -v' finally leading to a crash:

  BUG ext4_xattr: Freepointer corrupt
  ...
  BUG buffer_head: Freepointer corrupt
  ...
  BUG ext4_alloc_context: Freepointer corrupt
  ...
  ...
  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  IP: [<ffffffff810a291f>] file_sb_list_del+0x1c/0x35
  PGD 79d78067 PUD 79e67067 PMD 0
  Oops: 0002 [#1] SMP
  last sysfs file: /sys/kernel/slab/:t-0000192/validate

This patch fixes the problem by converting the two missed instances.

Signed-off-by: Tero Roponen <tero.roponen@...il.com>

diff --git a/mm/slub.c b/mm/slub.c
index 981fb73..bec0e35 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3401,13 +3401,13 @@ static int validate_slab(struct kmem_cache *s, struct page *page,

 	for_each_free_object(p, s, page->freelist) {
 		set_bit(slab_index(p, s, addr), map);
-		if (!check_object(s, page, p, 0))
+		if (!check_object(s, page, p, SLUB_RED_INACTIVE))
			return 0;
 	}

 	for_each_object(p, s, addr, page->objects)
 		if (!test_bit(slab_index(p, s, addr), map))
-			if (!check_object(s, page, p, 1))
+			if (!check_object(s, page, p, SLUB_RED_ACTIVE))
 				return 0;
 	return 1;
 }
--
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