Re: [PATCH] loop: fix LOOP_GET_STATUS lock imbalance

[Omar Sandoval <osandov@osandov.com>]

On Fri, Apr 06, 2018 at 09:57:03AM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Commit 2d1d4c1e591f made loop_get_status() drop lo_ctx_mutex before
> returning, but the loop_get_status_old(), loop_get_status64(), and
> loop_get_status_compat() wrappers don't call loop_get_status() if the
> passed argument is NULL. The callers expect that the lock is dropped, so
> make sure we drop it in that case, too.
> 
> Reported-by: syzbot+31e8daa8b3fc129e75f2@syzkaller.appspotmail.com
> Fixes: 2d1d4c1e591f ("loop: don't call into filesystem while holding lo_ctl_mutex")
> Signed-off-by: Omar Sandoval <osandov@fb.com>
> ---
> Based on Linus' tree.
> 
>  drivers/block/loop.c | 33 ++++++++++++++++++---------------
>  1 file changed, 18 insertions(+), 15 deletions(-)

Also just pushed a regression test to blktests:

140ee15de9f3 ("loop: add ioctl lock imbalance regression test")