linux-kernel - Re: [RFC 2/4] nbd: Split 'DO

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Message-ID: <CAECXXi5GcAbBzS+ATr2BRryJPvAUPCTMkmVT2TKWESG6anWuWw@mail.gmail.com>
Date:	Mon, 26 Jan 2015 11:16:12 -0500
From:	Paul Clements <paul.clements@...sios.com>
To:	Markus Pargmann <mpa@...gutronix.de>
Cc:	"nbd-general@...ts.sourceforge.net" 
	<nbd-general@...ts.sourceforge.net>,
	kernel list <linux-kernel@...r.kernel.org>,
	kernel@...gutronix.de
Subject: Re: [RFC 2/4] nbd: Split 'DO_IT' into three functions

Markus,

This refactor looks OK with the exception of one thing...

On Tue, Jan 13, 2015 at 8:44 AM, Markus Pargmann <mpa@...gutronix.de> wrote:

>  /* Must be called with tx_lock held */
>
>  static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
> @@ -684,61 +773,8 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
>                 set_capacity(nbd->disk, nbd->bytesize >> 9);
>                 return 0;
>
> -       case NBD_DO_IT: {
> -               struct task_struct *thread;
> -               struct socket *sock;
> -               int error;
> -
> -               if (nbd->pid)
> -                       return -EBUSY;
> -               if (!nbd->sock)
> -                       return -EINVAL;
>

You seem to have done away with these checks. Was that inadvertent or
was there a reason for that? The pid check is necessary to prevent two
instances of NBD_DO_IT from running. Without the sock check you'll get
a null pointer deref in nbd_do_it.

Thanks,
Paul
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