linux-kernel - Re: [PATCHv2] fs: Don't return 0 from get_anon

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Message-ID: <20140403203252.GA8855@kroah.com>
Date:	Thu, 3 Apr 2014 13:32:52 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Thomas Bächler <thomas@...hlinux.org>
Cc:	tj@...nel.org, d@...conindy.com, linux-kernel@...r.kernel.org,
	P@...igbrady.com, alexandre.f.demers@...il.com,
	"3.14" <stable@...r.kernel.org>
Subject: Re: [PATCHv2] fs: Don't return 0 from get_anon_bdev

On Thu, Apr 03, 2014 at 09:55:37PM +0200, Thomas Bächler wrote:
> Commit 9e30cc9595303b27b48 removed an internal mount. This
> has the side-effect that rootfs now has FSID 0. Many
> userspace utilities assume that st_dev in struct stat
> is never 0, so this change breaks a number of tools in
> early userspace.
> 
> Since we don't know how many userspace programs are affected,
> make sure that FSID is at least 1.
> 
> References: http://article.gmane.org/gmane.linux.kernel/1666905
> References: http://permalink.gmane.org/gmane.linux.utilities.util-linux-ng/8557
> Cc: 3.14 <stable@...r.kernel.org>
> Signed-off-by: Thomas Bächler <thomas@...hlinux.org>
> ---
>  fs/super.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/super.c b/fs/super.c
> index 80d5cf2..7624267 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -802,7 +802,10 @@ void emergency_remount(void)
>  
>  static DEFINE_IDA(unnamed_dev_ida);
>  static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
> -static int unnamed_dev_start = 0; /* don't bother trying below it */
> +/* Many userspace utilities consider an FSID of 0 invalid.
> + * Always return at least 1 from get_anon_bdev.
> + */
> +static int unnamed_dev_start = 1;
>  
>  int get_anon_bdev(dev_t *p)
>  {

Very nice, I'll go queue this one up instead of the other patch from
Tejun.

greg k-h
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