linux-kernel - Re: general protection fault in debugfs_create

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Date:   Thu, 31 Jan 2019 08:00:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     syzbot <syzbot+a9d09761be47db706560@...kaller.appspotmail.com>,
        axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: general protection fault in debugfs_create_files

On Thu, Jan 31, 2019 at 02:34:56PM +0900, Tetsuo Handa wrote:
> Hello, again.
> 
> syzbot is hitting a similar crash due to debugfs_create_dir() returning -EEXIST.
> Should debugfs_create_dir() return NULL as well? Or should the caller use IS_ERR_OR_NULL() ?
> 
> --- a/block/blk-mq-debugfs.c
> +++ b/block/blk-mq-debugfs.c
> @@ -861,6 +861,8 @@ int blk_mq_debugfs_register(struct request_queue *q)
>                                             blk_debugfs_root);
>         if (!q->debugfs_dir)
>                 return -ENOMEM;
> +       if (IS_ERR(q->debugfs_dir))
> +               printk("debugfs_create_dir=%ld\n", PTR_ERR(q->debugfs_dir));
> 
>         if (!debugfs_create_files(q->debugfs_dir, q,
>                                   blk_mq_debugfs_queue_attrs))
> 

I already posted this patch last Wednesday:
	https://lore.kernel.org/lkml/20190123134854.GA25906@kroah.com/
to solve this problem.

I guess I should queue it up in my tree as well, to handle this issue.
I'll go do that now.

thanks,

greg k-h