From: Mikulas Patocka Date: Tue, 3 Jun 2025 16:53:17 +0000 (+0200) Subject: dm-mirror: fix a tiny race condition X-Git-Url: http://git.monstr.eu/?a=commitdiff_plain;h=829451beaed6165eb11d7a9fb4e28eb17f489980;p=linux-2.6-microblaze.git dm-mirror: fix a tiny race condition There's a tiny race condition in dm-mirror. The functions queue_bio and write_callback grab a spinlock, add a bio to the list, drop the spinlock and wake up the mirrord thread that processes bios in the list. It may be possible that the mirrord thread processes the bio just after spin_unlock_irqrestore is called, before wakeup_mirrord. This spurious wake-up is normally harmless, however if the device mapper device is unloaded just after the bio was processed, it may be possible that wakeup_mirrord(ms) uses invalid "ms" pointer. Fix this bug by moving wakeup_mirrord inside the spinlock. Signed-off-by: Mikulas Patocka Cc: stable@vger.kernel.org --- diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c index 9e615b4f1f5e..785af4816584 100644 --- a/drivers/md/dm-raid1.c +++ b/drivers/md/dm-raid1.c @@ -133,10 +133,9 @@ static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw) spin_lock_irqsave(&ms->lock, flags); should_wake = !(bl->head); bio_list_add(bl, bio); - spin_unlock_irqrestore(&ms->lock, flags); - if (should_wake) wakeup_mirrord(ms); + spin_unlock_irqrestore(&ms->lock, flags); } static void dispatch_bios(void *context, struct bio_list *bio_list) @@ -646,9 +645,9 @@ static void write_callback(unsigned long error, void *context) if (!ms->failures.head) should_wake = 1; bio_list_add(&ms->failures, bio); - spin_unlock_irqrestore(&ms->lock, flags); if (should_wake) wakeup_mirrord(ms); + spin_unlock_irqrestore(&ms->lock, flags); } static void do_write(struct mirror_set *ms, struct bio *bio)