Commit b4efccec authored by Li Qiong's avatar Li Qiong Committed by Vlastimil Babka
Browse files

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



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: 81819f0f ("SLUB core")
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarLi Qiong <liqiong@nfschina.com>
Reviewed-by: default avatarHarry Yoo <harry.yoo@oracle.com>
Reviewed-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
parent 1b237f19

mm/slub.c

+6 −1
Original line number Diff line number Diff line
@@ -1140,7 +1140,12 @@ static void object_err(struct kmem_cache *s, struct slab *slab, 
		return;



	slab_bug(s, reason);

	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);