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mm/slub: avoid accessing metadata when pointer is invalid in object_err()

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object_err() reports details of an object for further debugging, such as
the freelist pointer, redzone, etc. However, if the pointer is invalid,
attempting to access object metadata can lead to a crash since it does
not point to a valid object.

One known path to the crash is when alloc_consistency_checks()
determines the pointer to the allocated object is invalid because of a
freelist corruption, and calls object_err() to report it. The debug code
should report and handle the corruption gracefully and not crash in the
process.

In case the pointer is NULL or check_valid_pointer() returns false for
the pointer, only print the pointer value and skip accessing metadata.

Fixes: 81819f0fc8 ("SLUB core")
Cc: <stable@vger.kernel.org>
Signed-off-by: Li Qiong <liqiong@nfschina.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
This commit is contained in:
Li Qiong 2025-08-04 10:57:59 +08:00 committed by Vlastimil Babka
parent 1b237f190e
commit b4efccec8d
1 changed files with 6 additions and 1 deletions
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7
mm/slub.c
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@ -1140,7 +1140,12 @@ static void object_err(struct kmem_cache *s, struct slab *slab,
return;
slab_bug(s, reason);
print_trailer(s, slab, object);
if (!object || !check_valid_pointer(s, slab, object)) {
print_slab_info(slab);
pr_err("Invalid pointer 0x%p\n", object);
} else {
print_trailer(s, slab, object);
}
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
WARN_ON(1);