diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2023-11-29 13:38:43 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-12-08 08:44:25 +0100 |
| commit | a658ee7930116a71665eae9f740b4c7d054d1002 (patch) | |
| tree | 027e97a82201abf883af2ab7a13d09ff41e67514 | |
| parent | ef918a1ba40c2b65229b4c48138b2188673ffbbc (diff) | |
dm-delay: fix a race between delay_presuspend and delay_bio
[ Upstream commit 6fc45b6ed921dc00dfb264dc08c7d67ee63d2656 ]
In delay_presuspend, we set the atomic variable may_delay and then stop
the timer and flush pending bios. The intention here is to prevent the
delay target from re-arming the timer again.
However, this test is racy. Suppose that one thread goes to delay_bio,
sees that dc->may_delay is one and proceeds; now, another thread executes
delay_presuspend, it sets dc->may_delay to zero, deletes the timer and
flushes pending bios. Then, the first thread continues and adds the bio to
delayed->list despite the fact that dc->may_delay is false.
Fix this bug by changing may_delay's type from atomic_t to bool and
only access it while holding the delayed_bios_lock mutex. Note that we
don't have to grab the mutex in delay_resume because there are no bios
in flight at this point.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/md/dm-delay.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c index f496213f8b67..7c0e7c662e07 100644 --- a/drivers/md/dm-delay.c +++ b/drivers/md/dm-delay.c @@ -30,7 +30,7 @@ struct delay_c { struct workqueue_struct *kdelayd_wq; struct work_struct flush_expired_bios; struct list_head delayed_bios; - atomic_t may_delay; + bool may_delay; struct delay_class read; struct delay_class write; @@ -191,7 +191,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) INIT_WORK(&dc->flush_expired_bios, flush_expired_bios); INIT_LIST_HEAD(&dc->delayed_bios); mutex_init(&dc->timer_lock); - atomic_set(&dc->may_delay, 1); + dc->may_delay = true; dc->argc = argc; ret = delay_class_ctr(ti, &dc->read, argv); @@ -245,7 +245,7 @@ static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio) struct dm_delay_info *delayed; unsigned long expires = 0; - if (!c->delay || !atomic_read(&dc->may_delay)) + if (!c->delay) return DM_MAPIO_REMAPPED; delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info)); @@ -254,6 +254,10 @@ static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio) delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay); mutex_lock(&delayed_bios_lock); + if (unlikely(!dc->may_delay)) { + mutex_unlock(&delayed_bios_lock); + return DM_MAPIO_REMAPPED; + } c->ops++; list_add_tail(&delayed->list, &dc->delayed_bios); mutex_unlock(&delayed_bios_lock); @@ -267,7 +271,10 @@ static void delay_presuspend(struct dm_target *ti) { struct delay_c *dc = ti->private; - atomic_set(&dc->may_delay, 0); + mutex_lock(&delayed_bios_lock); + dc->may_delay = false; + mutex_unlock(&delayed_bios_lock); + del_timer_sync(&dc->delay_timer); flush_bios(flush_delayed_bios(dc, 1)); } @@ -276,7 +283,7 @@ static void delay_resume(struct dm_target *ti) { struct delay_c *dc = ti->private; - atomic_set(&dc->may_delay, 1); + dc->may_delay = true; } static int delay_map(struct dm_target *ti, struct bio *bio) |