Re: [PATCH 14/19] fs: Permit FIBMAP for users with CAP_SYS_RAWIO in s_user_ns

From: Theodore Ts'o <tytso@mit.edu>
To: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Seth Forshee <seth.forshee@canonical.com>,
	"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 14/19] fs: Permit FIBMAP for users with CAP_SYS_RAWIO in s_user_ns
Date: Fri, 4 Dec 2015 15:05:28 -0500	[thread overview]
Message-ID: <20151204200528.GC18359@thunk.org> (raw)
In-Reply-To: <20151204191143.GE3624@mail.hallyn.com>

The fact that we need CAP_SYS_RAIO for FIBMAP is pretty silly, given
that FIEMAP does not require privileges --- and in fact the preferred
interface.  Why not just simply drop the requirement for privileges
for FIBMAP?

(Seth, Serge, this isn't a real objection to your patch; but the fact
that FIBMAP requires root has always been a bit silly, and this would
be a great opportunity to simplify things a bit.)

						- Ted

On Fri, Dec 04, 2015 at 01:11:43PM -0600, Serge E. Hallyn wrote:
> Quoting Seth Forshee (seth.forshee@canonical.com):
> > Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
> 
> Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
> 
> > ---
> >  fs/ioctl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/ioctl.c b/fs/ioctl.c
> > index 5d01d2638ca5..45c371bed7ee 100644
> > --- a/fs/ioctl.c
> > +++ b/fs/ioctl.c
> > @@ -55,7 +55,7 @@ static int ioctl_fibmap(struct file *filp, int __user *p)
> >  	/* do we support this mess? */
> >  	if (!mapping->a_ops->bmap)
> >  		return -EINVAL;
> > -	if (!capable(CAP_SYS_RAWIO))
> > +	if (!ns_capable(filp->f_inode->i_sb->s_user_ns, CAP_SYS_RAWIO))
> >  		return -EPERM;
> >  	res = get_user(block, p);
> >  	if (res)
> > -- 
> > 1.9.1
> > 
> > --
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