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author | Mike Snitzer <snitzer@redhat.com> | 2015-03-23 21:01:43 (GMT) |
---|---|---|
committer | Mike Snitzer <snitzer@redhat.com> | 2015-03-23 22:14:00 (GMT) |
commit | 63a4f065ece613b6d575b538234375b0e9c23bbc (patch) | |
tree | e1a7896387c308886622e6b7edd3f5225873fa0f /drivers/md | |
parent | e5db29806b99ce2b2640d2e4d4fcb983cea115c5 (diff) | |
download | linux-63a4f065ece613b6d575b538234375b0e9c23bbc.tar.xz |
dm: fix add_disk() NULL pointer due to race with free_dev()
Commit c4db59d31e39 ("fs: don't reassign dirty inodes to
default_backing_dev_info") exposed DM to a latent race in free_dev() vs
add_disk() in relation to management of the device's minor number.
Fix this by refactoring free_dev() to match cleanup order of the
alloc_dev() error path. Move cleanup of the gendisk, queue, and bdev
to _before_ the cleanup of the idr managed minor number.
Also, purely due to cleanup that fell out during the free_dev() audit:
- adjust dm_blk_close() to access the gendisk's private_data under
the _minor_lock spinlock.
- move __dm_destroy()'s dm_get_live_table() call out from under the
_minor_lock spinlock.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1202449
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r-- | drivers/md/dm.c | 26 |
1 files changed, 16 insertions, 10 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 9b641b3..8001fe9 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -433,7 +433,6 @@ static int dm_blk_open(struct block_device *bdev, fmode_t mode) dm_get(md); atomic_inc(&md->open_count); - out: spin_unlock(&_minor_lock); @@ -442,16 +441,20 @@ out: static void dm_blk_close(struct gendisk *disk, fmode_t mode) { - struct mapped_device *md = disk->private_data; + struct mapped_device *md; spin_lock(&_minor_lock); + md = disk->private_data; + if (WARN_ON(!md)) + goto out; + if (atomic_dec_and_test(&md->open_count) && (test_bit(DMF_DEFERRED_REMOVE, &md->flags))) queue_work(deferred_remove_workqueue, &deferred_remove_work); dm_put(md); - +out: spin_unlock(&_minor_lock); } @@ -2241,7 +2244,6 @@ static void free_dev(struct mapped_device *md) int minor = MINOR(disk_devt(md->disk)); unlock_fs(md); - bdput(md->bdev); destroy_workqueue(md->wq); if (md->kworker_task) @@ -2252,19 +2254,22 @@ static void free_dev(struct mapped_device *md) mempool_destroy(md->rq_pool); if (md->bs) bioset_free(md->bs); - blk_integrity_unregister(md->disk); - del_gendisk(md->disk); + cleanup_srcu_struct(&md->io_barrier); free_table_devices(&md->table_devices); - free_minor(minor); + dm_stats_cleanup(&md->stats); spin_lock(&_minor_lock); md->disk->private_data = NULL; spin_unlock(&_minor_lock); - + if (blk_get_integrity(md->disk)) + blk_integrity_unregister(md->disk); + del_gendisk(md->disk); put_disk(md->disk); blk_cleanup_queue(md->queue); - dm_stats_cleanup(&md->stats); + bdput(md->bdev); + free_minor(minor); + module_put(THIS_MODULE); kfree(md); } @@ -2642,8 +2647,9 @@ static void __dm_destroy(struct mapped_device *md, bool wait) might_sleep(); - spin_lock(&_minor_lock); map = dm_get_live_table(md, &srcu_idx); + + spin_lock(&_minor_lock); idr_replace(&_minor_idr, MINOR_ALLOCED, MINOR(disk_devt(dm_disk(md)))); set_bit(DMF_FREEING, &md->flags); spin_unlock(&_minor_lock); |