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fanotify: stop permission watchdog when timeout is zero

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The fanotify permission watchdog can be disabled by writing zero to
fs/fanotify/watchdog_timeout.  fanotify_perm_watchdog_group_add() already
checks for a zero timeout before scheduling the watchdog.

However, once the watchdog work has been scheduled, perm_group_watchdog()
unconditionally schedules itself again with the current timeout.  If the
sysctl is changed to zero while the work is active, secs_to_jiffies(0)
causes the work to be rescheduled immediately, resulting in a kworker
busy loop.

Read the timeout once in perm_group_watchdog_schedule() and do not
schedule the work when it is zero.  This lets a running watchdog stop
after the next execution when the sysctl is set to zero.

Fixes: b8cf8fda52 ("fanotify: add watchdog for permission events")
Signed-off-by: Yichong Chen <chenyichong@uniontech.com>
Link: https://patch.msgid.link/20260730070648.549458-1-chenyichong@uniontech.com
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Yichong Chen 2026-07-30 15:06:48 +08:00 committed by Jan Kara
parent 44afeafb88
commit 17463fe751
1 changed files with 6 additions and 1 deletions
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7
fs/notify/fanotify/fanotify_user.c
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@ -112,7 +112,12 @@ static DECLARE_DELAYED_WORK(perm_group_work, perm_group_watchdog);
static void perm_group_watchdog_schedule(void)
{
schedule_delayed_work(&perm_group_work, secs_to_jiffies(perm_group_timeout));
int timeout = READ_ONCE(perm_group_timeout);
if (!timeout)
return;
schedule_delayed_work(&perm_group_work, secs_to_jiffies(timeout));
}
static void perm_group_watchdog(struct work_struct *work)