summaryrefslogtreecommitdiff
path: root/drivers/md
diff options
context:
space:
mode:
authorMikulas Patocka <mpatocka@redhat.com>2023-11-17 20:21:14 +0300
committerMike Snitzer <snitzer@kernel.org>2023-11-17 22:38:46 +0300
commit6fc45b6ed921dc00dfb264dc08c7d67ee63d2656 (patch)
treebd99f7681d41331bb1fc88a47d7ec26229414ebc /drivers/md
parentb85ea95d086471afb4ad062012a4d73cd328fa86 (diff)
downloadlinux-6fc45b6ed921dc00dfb264dc08c7d67ee63d2656.tar.xz
dm-delay: fix a race between delay_presuspend and delay_bio
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>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-delay.c16
1 files changed, 11 insertions, 5 deletions
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index efd510984e25..2d6b900e4353 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -33,7 +33,7 @@ struct delay_c {
struct work_struct flush_expired_bios;
struct list_head delayed_bios;
struct task_struct *worker;
- atomic_t may_delay;
+ bool may_delay;
struct delay_class read;
struct delay_class write;
@@ -236,7 +236,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
ti->private = dc;
INIT_LIST_HEAD(&dc->delayed_bios);
- atomic_set(&dc->may_delay, 1);
+ dc->may_delay = true;
dc->argc = argc;
ret = delay_class_ctr(ti, &dc->read, argv);
@@ -312,7 +312,7 @@ 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));
@@ -321,6 +321,10 @@ 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);
@@ -337,7 +341,9 @@ 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);
if (delay_is_fast(dc))
flush_delayed_bios_fast(dc, true);
@@ -351,7 +357,7 @@ 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)