Patch "mm: kfence: fix using kfence_metadata without initialization in show_object()" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    mm: kfence: fix using kfence_metadata without initialization in show_object()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mm-kfence-fix-using-kfence_metadata-without-initialization-in-show_object.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 1c86a188e03156223a34d09ce290b49bd4dd0403 Mon Sep 17 00:00:00 2001
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Date: Wed, 15 Mar 2023 11:44:41 +0800
Subject: mm: kfence: fix using kfence_metadata without initialization in show_object()

From: Muchun Song <songmuchun@xxxxxxxxxxxxx>

commit 1c86a188e03156223a34d09ce290b49bd4dd0403 upstream.

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@xxxxxxxxxxxxx
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Tested-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: SeongJae Park <sjpark@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/kfence/core.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -678,10 +678,14 @@ static const struct file_operations obje
 	.release = seq_release,
 };
 
-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;


Patches currently in stable-queue which might be from songmuchun@xxxxxxxxxxxxx are

queue-5.15/mm-kfence-fix-using-kfence_metadata-without-initialization-in-show_object.patch



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