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| author | Marc Dionne <marc.c.dionne@gmail.com> | 2014-12-17 07:59:59 -0500 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2014-12-17 12:06:25 -0500 |
| commit | 2b94e8960cc3f225dec058f27570505351f4bc13 (patch) | |
| tree | 107ad9a40ce7a12e424b38c636d28de19be93556 /drivers/md | |
| parent | 2c43fd26e46734430122b8d2ad3024bb532df3ef (diff) | |
| download | linux-2b94e8960cc3f225dec058f27570505351f4bc13.tar.bz2 | |
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')
| -rw-r--r-- | drivers/md/dm-thin.c | 5 |
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) dm_put(pool_md); - atomic_set(&tc->refcount, 1); - init_completion(&tc->can_destroy); - return 0; bad: |