path: root/drivers/md/dm-thin.c
diff options
authorMarc Dionne <marc.c.dionne@gmail.com>2014-12-17 07:59:59 -0500
committerMike Snitzer <snitzer@redhat.com>2014-12-17 12:06:25 -0500
commit2b94e8960cc3f225dec058f27570505351f4bc13 (patch)
tree107ad9a40ce7a12e424b38c636d28de19be93556 /drivers/md/dm-thin.c
parent2c43fd26e46734430122b8d2ad3024bb532df3ef (diff)
dm thin: fix crash by initializing thin device's refcount and completion earlier
Commit 80e96c5484be ("dm thin: do not allow thin device activation while pool is suspended") delayed the initialization of a new thin device's refcount and completion until after this new thin was added to the pool's active_thins list and the pool lock is released. This opens a race with a worker thread that walks the list and calls thin_get/put, noticing that the refcount goes to 0 and calling complete, freezing up the system and giving the oops below: kernel: BUG: unable to handle kernel NULL pointer dereference at (null) kernel: IP: [<ffffffff810d360b>] __wake_up_common+0x2b/0x90 kernel: Call Trace: kernel: [<ffffffff810d3683>] __wake_up_locked+0x13/0x20 kernel: [<ffffffff810d3dc7>] complete+0x37/0x50 kernel: [<ffffffffa0595c50>] thin_put+0x20/0x30 [dm_thin_pool] kernel: [<ffffffffa059aab7>] do_worker+0x667/0x870 [dm_thin_pool] kernel: [<ffffffff816a8a4c>] ? __schedule+0x3ac/0x9a0 kernel: [<ffffffff810b1aef>] process_one_work+0x14f/0x400 kernel: [<ffffffff810b206b>] worker_thread+0x6b/0x490 kernel: [<ffffffff810b2000>] ? rescuer_thread+0x260/0x260 kernel: [<ffffffff810b6a7b>] kthread+0xdb/0x100 kernel: [<ffffffff810b69a0>] ? kthread_create_on_node+0x170/0x170 kernel: [<ffffffff816ad7ec>] ret_from_fork+0x7c/0xb0 kernel: [<ffffffff810b69a0>] ? kthread_create_on_node+0x170/0x170 Set the thin device's initial refcount and initialize the completion before adding it to the pool's active_thins list in thin_ctr(). Signed-off-by: Marc Dionne <marc.dionne@your-file-system.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-thin.c')
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 922aa553e9e0..493478989dbd 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -3832,6 +3832,8 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
r = -EINVAL;
goto bad;
+ atomic_set(&tc->refcount, 1);
+ init_completion(&tc->can_destroy);
list_add_tail_rcu(&tc->list, &tc->pool->active_thins);
spin_unlock_irqrestore(&tc->pool->lock, flags);
@@ -3844,9 +3846,6 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
- atomic_set(&tc->refcount, 1);
- init_completion(&tc->can_destroy);
return 0;