2010-12-01 18:04:23

by Tero Roponen

[permalink] [raw]
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 <[email protected]>

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;
}


Subject: Re: [PATCH] slub: Fix a crash during slabinfo -v

On Wed, 1 Dec 2010, Tero Roponen wrote:

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

Hmmm...A hunk was dropped somewhere.

Acked-by: Christoph Lameter <[email protected]>