From: Li Qiong Date: Sun, 7 Sep 2025 01:17:23 +0000 (-0400) Subject: mm/slub: avoid accessing metadata when pointer is invalid in object_err() X-Git-Tag: v6.6.105~42 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0ef7058b4dc6fcef622ac23b45225db57f17b83f;p=thirdparty%2Fkernel%2Fstable.git mm/slub: avoid accessing metadata when pointer is invalid in object_err() [ Upstream commit b4efccec8d06ceb10a7d34d7b1c449c569d53770 ] 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: 81819f0fc828 ("SLUB core") Cc: Signed-off-by: Li Qiong Reviewed-by: Harry Yoo Reviewed-by: Matthew Wilcox (Oracle) Signed-off-by: Vlastimil Babka [ Adjust context ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- diff --git a/mm/slub.c b/mm/slub.c index d2544c88a5c43..391f9db1c8f38 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -988,7 +988,12 @@ static void object_err(struct kmem_cache *s, struct slab *slab, return; slab_bug(s, "%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); }