Date: Fri, 4 Dec 2015 10:28:07 -0600
From: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
To: Seth Forshee <seth.forshee@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        Richard Weinberger <richard.weinberger@gmail.com>,
        Austin S Hemmelgarn <ahferroin7@gmail.com>,
        Miklos Szeredi <miklos@szeredi.hu>, linux-bcache@vger.kernel.org,
        dm-devel@redhat.com, linux-raid@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
        linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net,
        linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov
Subject: Re: [PATCH 02/19] block_dev: Check permissions towards block device
 inode when mounting
Message-ID: <20151204162807.GB1722@mail.hallyn.com>
References: <1449070821-73820-1-git-send-email-seth.forshee@canonical.com>
 <1449070821-73820-3-git-send-email-seth.forshee@canonical.com>
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On Wed, Dec 02, 2015 at 09:40:02AM -0600, Seth Forshee wrote:
> Unprivileged users should not be able to mount block devices when
> they lack sufficient privileges towards the block device inode.
> Update blkdev_get_by_path() to validate that the user has the
> required access to the inode at the specified path. The check
> will be skipped for CAP_SYS_ADMIN, so privileged mounts will
> continue working as before.
> 
> Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>

> ---
>  fs/block_dev.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 3ebbde85d898..4fdb6ab59816 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1424,9 +1424,14 @@ struct block_device *blkdev_get_by_path(const char *path, fmode_t mode,
>  					void *holder)
>  {
>  	struct block_device *bdev;
> +	int perm = 0;
>  	int err;
>  
> -	bdev = lookup_bdev(path, 0);
> +	if (mode & FMODE_READ)
> +		perm |= MAY_READ;
> +	if (mode & FMODE_WRITE)
> +		perm |= MAY_WRITE;
> +	bdev = lookup_bdev(path, perm);
>  	if (IS_ERR(bdev))
>  		return bdev;
>  
> -- 
> 1.9.1
> 
> --
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