diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2015-02-17 22:30:53 +0300 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-02-18 17:41:19 +0300 |
| commit | 2bec1f4a8832e74ebbe859f176d8a9cb20dd97f4 (patch) | |
| tree | b9d1da979b02b7f026e4b1db91ccc6022096567b | |
| parent | b3c5fd3052492f1b8d060799d4f18be5a5438add (diff) | |
| download | linux-2bec1f4a8832e74ebbe859f176d8a9cb20dd97f4.tar.xz | |
dm: fix a race condition in dm_get_md
The function dm_get_md finds a device mapper device with a given dev_t,
increases the reference count and returns the pointer.
dm_get_md calls dm_find_md, dm_find_md takes _minor_lock, finds the
device, tests that the device doesn't have DMF_DELETING or DMF_FREEING
flag, drops _minor_lock and returns pointer to the device. dm_get_md then
calls dm_get. dm_get calls BUG if the device has the DMF_FREEING flag,
otherwise it increments the reference count.
There is a possible race condition - after dm_find_md exits and before
dm_get is called, there are no locks held, so the device may disappear or
DMF_FREEING flag may be set, which results in BUG.
To fix this bug, we need to call dm_get while we hold _minor_lock. This
patch renames dm_find_md to dm_get_md and changes it so that it calls
dm_get while holding the lock.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
| -rw-r--r-- | drivers/md/dm.c | 27 |
1 files changed, 10 insertions, 17 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index ec1444f49de1..73f28802dc7a 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2571,7 +2571,7 @@ int dm_setup_md_queue(struct mapped_device *md) return 0; } -static struct mapped_device *dm_find_md(dev_t dev) +struct mapped_device *dm_get_md(dev_t dev) { struct mapped_device *md; unsigned minor = MINOR(dev); @@ -2582,12 +2582,15 @@ static struct mapped_device *dm_find_md(dev_t dev) spin_lock(&_minor_lock); md = idr_find(&_minor_idr, minor); - if (md && (md == MINOR_ALLOCED || - (MINOR(disk_devt(dm_disk(md))) != minor) || - dm_deleting_md(md) || - test_bit(DMF_FREEING, &md->flags))) { - md = NULL; - goto out; + if (md) { + if ((md == MINOR_ALLOCED || + (MINOR(disk_devt(dm_disk(md))) != minor) || + dm_deleting_md(md) || + test_bit(DMF_FREEING, &md->flags))) { + md = NULL; + goto out; + } + dm_get(md); } out: @@ -2595,16 +2598,6 @@ out: return md; } - -struct mapped_device *dm_get_md(dev_t dev) -{ - struct mapped_device *md = dm_find_md(dev); - - if (md) - dm_get(md); - - return md; -} EXPORT_SYMBOL_GPL(dm_get_md); void *dm_get_mdptr(struct mapped_device *md) |