linux-kernel - [PATCH v2] fsnotify: initialize destroy_next to avoid KMSAN uninit-value warning

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Message-ID: <20250619105117.106907-1-abinashsinghlalotra@gmail.com>
Date: Thu, 19 Jun 2025 16:21:17 +0530
From: avinashlalotra <abinashlalotra@...il.com>
To: jack@...e.cz,
	amir73il@...il.com
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	avinashlalotra <abinashsinghlalotra@...il.com>,
	syzbot+aaeb1646d01d0358cb2a@...kaller.appspotmail.com
Subject: [PATCH v2] fsnotify: initialize destroy_next to avoid KMSAN uninit-value warning

KMSAN reported an uninitialized value use in
fsnotify_connector_destroy_workfn(), specifically when accessing
`conn->destroy_next`:

    BUG: KMSAN: uninit-value in fsnotify_connector_destroy_workfn+0x108/0x160
    Uninit was created at:
     slab_alloc_node mm/slub.c:4197 [inline]
     kmem_cache_alloc_noprof+0x81b/0xec0 mm/slub.c:4204
     fsnotify_attach_connector_to_object fs/notify/mark.c:663

The struct fsnotify_mark_connector was allocated using
kmem_cache_alloc(), but the `destroy_next` field was never initialized,
leading to a use of uninitialized memory when the work function later
traversed the destroy list.

Fix this by explicitly initializing `destroy_next` to NULL immediately
after allocation.

Reported-by: syzbot+aaeb1646d01d0358cb2a@...kaller.appspotmail.com
Signed-off-by: abinashlalotra <abinashsinghlalotra@...il.com>

---
v2: Corrected the syzbot Reported-by email address.
---
 fs/notify/mark.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 798340db69d7..28013046f732 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -665,6 +665,7 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
 		return -ENOMEM;
 	spin_lock_init(&conn->lock);
 	INIT_HLIST_HEAD(&conn->list);
+	conn->destroy_next = NULL;
 	conn->flags = 0;
 	conn->prio = 0;
 	conn->type = obj_type;
-- 
2.43.0