FAILED: patch "[PATCH] mm/slub: avoid accessing metadata when pointer is invalid in" failed to apply to 6.1-stable tree

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 <[email protected]>.

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 '<[email protected]>' --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 <[email protected]>
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.

index 30003763d224..1787e4d51e48 100644
@@ -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);

From: Li Qiong <[email protected]>

[ 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.

---
 mm/slub.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

index 157527d7101be..f118fcc6af6e4 100644
@@ -927,7 +927,12 @@ 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);
 }
 

2.51.0