The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x b4efccec8d06ceb10a7d34d7b1c449c569d53770 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025090620-evaluator-visiting-ac7e@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b4efccec8d06ceb10a7d34d7b1c449c569d53770 Mon Sep 17 00:00:00 2001 From: Li Qiong liqiong@nfschina.com Date: Mon, 4 Aug 2025 10:57:59 +0800 Subject: [PATCH] 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: 81819f0fc828 ("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

diff --git a/mm/slub.c b/mm/slub.c index 30003763d224..1787e4d51e48 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -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);