Re: WARNING: locking bug in loop_control_ioctl

[Ming Lei]

On Sat, Nov 10, 2018 at 05:09:09PM +0900, Tetsuo Handa wrote:
> From 4b9e5556fada37dff1eff13665a229b69e1f7dd8 Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Date: Sat, 10 Nov 2018 17:04:40 +0900
> Subject: [PATCH] loop: Fix double mutex_unlock(&loop_ctl_mutex) in loop_control_ioctl().
> 
> Commit 0a42e99b58a20883 ("loop: Get rid of loop_index_mutex") forgot to
> remove mutex_unlock(&loop_ctl_mutex) from loop_control_ioctl() when
> replacing loop_index_mutex with loop_ctl_mutex.
> 
> Reported-by: syzbot <syzbot+c0138741c2290fc5e63f@xxxxxxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Cc: Jan Kara <jack@xxxxxxx>
> ---
>  drivers/block/loop.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index bf6bc35..176ab1f 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -2074,12 +2074,10 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
>  			break;
>  		if (lo->lo_state != Lo_unbound) {
>  			ret = -EBUSY;
> -			mutex_unlock(&loop_ctl_mutex);
>  			break;
>  		}
>  		if (atomic_read(&lo->lo_refcnt) > 0) {
>  			ret = -EBUSY;
> -			mutex_unlock(&loop_ctl_mutex);
>  			break;
>  		}
>  		lo->lo_disk->private_data = NULL;
> -- 
> 1.8.3.1
> 

Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>

-- 
Ming