FAILED: patch "[PATCH] mm: kfence: fix using kfence_metadata without initialization" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 1c86a188e03156223a34d09ce290b49bd4dd0403
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '16800049118459@kroah.com' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

1c86a188e031 ("mm: kfence: fix using kfence_metadata without initialization in show_object()")
b33f778bba5e ("kfence: alloc kfence_pool after system startup")
698361bca2d5 ("kfence: allow re-enabling KFENCE after system startup")
07e8481d3c38 ("kfence: always use static branches to guard kfence_alloc()")
08f6b10630f2 ("kfence: limit currently covered allocations when pool nearly full")
a9ab52bbcb52 ("kfence: move saving stack trace of allocations into __kfence_alloc()")
9a19aeb56650 ("kfence: count unexpectedly skipped allocations")

thanks,

greg k-h

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

From 1c86a188e03156223a34d09ce290b49bd4dd0403 Mon Sep 17 00:00:00 2001
From: Muchun Song <muchun.song@linux.dev>
Date: Wed, 15 Mar 2023 11:44:41 +0800
Subject: [PATCH] mm: kfence: fix using kfence_metadata without initialization
 in show_object()

The variable kfence_metadata is initialized in kfence_init_pool(), then,
it is not initialized if kfence is disabled after booting.  In this case,
kfence_metadata will be used (e.g.  ->lock and ->state fields) without
initialization when reading /sys/kernel/debug/kfence/objects.  There will
be a warning if you enable CONFIG_DEBUG_SPINLOCK.  Fix it by creating
debugfs files when necessary.

Link: https://lkml.kernel.org/r/20230315034441.44321-1-songmuchun@bytedance.com
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Tested-by: Marco Elver <elver@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: SeongJae Park <sjpark@amazon.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index 5349c37a5dac..79c94ee55f97 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -726,10 +726,14 @@ static const struct seq_operations objects_sops = {
 };
 DEFINE_SEQ_ATTRIBUTE(objects);
 
-static int __init kfence_debugfs_init(void)
+static int kfence_debugfs_init(void)
 {
-	struct dentry *kfence_dir = debugfs_create_dir("kfence", NULL);
+	struct dentry *kfence_dir;
 
+	if (!READ_ONCE(kfence_enabled))
+		return 0;
+
+	kfence_dir = debugfs_create_dir("kfence", NULL);
 	debugfs_create_file("stats", 0444, kfence_dir, NULL, &stats_fops);
 	debugfs_create_file("objects", 0400, kfence_dir, NULL, &objects_fops);
 	return 0;
@@ -883,6 +887,8 @@ static int kfence_init_late(void)
 	}
 
 	kfence_init_enable();
+	kfence_debugfs_init();
+
 	return 0;
 }