The patch titled Subject: mm: kfence: fix using kfence_metadata without initialization in show_object() has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-kfence-fix-using-kfence_metadata-without-initialization-in-show_object.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Muchun Song songmuchun@bytedance.com Subject: mm: kfence: fix using kfence_metadata without initialization in show_object() Date: Wed, 15 Mar 2023 11:44:41 +0800

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 ---

mm/kfence/core.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/mm/kfence/core.c~mm-kfence-fix-using-kfence_metadata-without-initialization-in-show_object +++ a/mm/kfence/core.c @@ -726,10 +726,14 @@ static const struct seq_operations objec }; 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; }

_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-kfence-fix-using-kfence_metadata-without-initialization-in-show_object.patch mm-hugetlb_vmemmap-simplify-hugetlb_vmemmap_init-a-bit.patch