The patch titled Subject: nilfs2: avoid having an active sc_timer before freeing sci has been added to the -mm mm-hotfixes-unstable branch. Its filename is nilfs2-avoid-having-an-active-sc_timer-before-freeing-sci.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: Edward Adam Davis eadavis@qq.com Subject: nilfs2: avoid having an active sc_timer before freeing sci Date: Thu, 30 Oct 2025 07:51:52 +0900

Because kthread_stop did not stop sc_task properly and returned -EINTR, the sc_timer was not properly closed, ultimately causing the problem [1] reported by syzbot when freeing sci due to the sc_timer not being closed.

Because the thread sc_task main function nilfs_segctor_thread() returns 0 when it succeeds, when the return value of kthread_stop() is not 0 in nilfs_segctor_destroy(), we believe that it has not properly closed sc_timer.

We use timer_shutdown_sync() to sync wait for sc_timer to shutdown, and set the value of sc_task to NULL under the protection of lock sc_state_lock, so as to avoid the issue caused by sc_timer not being properly shutdowned.

[1] ODEBUG: free active (active state 0) object: 00000000dacb411a object type: timer_list hint: nilfs_construction_timeout Call trace: nilfs_segctor_destroy fs/nilfs2/segment.c:2811 [inline] nilfs_detach_log_writer+0x668/0x8cc fs/nilfs2/segment.c:2877 nilfs_put_super+0x4c/0x12c fs/nilfs2/super.c:509

Link: https://lkml.kernel.org/r/20251029225226.16044-1-konishi.ryusuke@gmail.com Fixes: 3f66cc261ccb ("nilfs2: use kthread_create and kthread_stop for the log writer thread") Signed-off-by: Ryusuke Konishi konishi.ryusuke@gmail.com Reported-by: syzbot+24d8b70f039151f65590@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=24d8b70f039151f65590 Tested-by: syzbot+24d8b70f039151f65590@syzkaller.appspotmail.com Signed-off-by: Edward Adam Davis eadavis@qq.com Cc: stable@vger.kernel.org [6.12+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/nilfs2/segment.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/fs/nilfs2/segment.c~nilfs2-avoid-having-an-active-sc_timer-before-freeing-sci +++ a/fs/nilfs2/segment.c @@ -2768,7 +2768,12 @@ static void nilfs_segctor_destroy(struct

if (sci->sc_task) { wake_up(&sci->sc_wait_daemon); - kthread_stop(sci->sc_task); + if (kthread_stop(sci->sc_task)) { + spin_lock(&sci->sc_state_lock); + sci->sc_task = NULL; + timer_shutdown_sync(&sci->sc_timer); + spin_unlock(&sci->sc_state_lock); + } }

spin_lock(&sci->sc_state_lock); _

Patches currently in -mm which might be from eadavis@qq.com are

nilfs2-avoid-having-an-active-sc_timer-before-freeing-sci.patch