From: Mike Snitzer <snitzer@xxxxxxxxxx> commit 3d32aaa7e66d5c1479a3c31d6c2c5d45dd0d3b89 upstream. syzkaller found the following problematic rwsem locking (with write lock already held): down_read+0x9d/0x450 kernel/locking/rwsem.c:1509 dm_get_inactive_table+0x2b/0xc0 drivers/md/dm-ioctl.c:773 __dev_status+0x4fd/0x7c0 drivers/md/dm-ioctl.c:844 table_clear+0x197/0x280 drivers/md/dm-ioctl.c:1537 In table_clear, it first acquires a write lock https://elixir.bootlin.com/linux/v6.2/source/drivers/md/dm-ioctl.c#L1520 down_write(&_hash_lock); Then before the lock is released at L1539, there is a path shown above: table_clear -> __dev_status -> dm_get_inactive_table -> down_read https://elixir.bootlin.com/linux/v6.2/source/drivers/md/dm-ioctl.c#L773 down_read(&_hash_lock); It tries to acquire the same read lock again, resulting in the deadlock problem. Fix this by moving table_clear()'s __dev_status() call to after its up_write(&_hash_lock); Cc: stable@xxxxxxxxxxxxxxx Reported-by: Zheng Zhang <zheng.zhang@xxxxxxxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/dm-ioctl.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1533,11 +1533,12 @@ static int table_clear(struct file *filp has_new_map = true; } - param->flags &= ~DM_INACTIVE_PRESENT_FLAG; - - __dev_status(hc->md, param); md = hc->md; up_write(&_hash_lock); + + param->flags &= ~DM_INACTIVE_PRESENT_FLAG; + __dev_status(md, param); + if (old_map) { dm_sync_table(md); dm_table_destroy(old_map);
