linux-kernel - Re: [PATCH 14/19] fs: Permit FIBMAP for users with CAP_SYS_RAWIO in s_user

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Message-ID: <20151204200736.GJ3624@mail.hallyn.com>
Date:	Fri, 4 Dec 2015 14:07:36 -0600
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Theodore Ts'o <tytso@....edu>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Seth Forshee <seth.forshee@...onical.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Richard Weinberger <richard.weinberger@...il.com>,
	Austin S Hemmelgarn <ahferroin7@...il.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	linux-bcache@...r.kernel.org, dm-devel@...hat.com,
	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mtd@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
	fuse-devel@...ts.sourceforge.net,
	linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov
Subject: Re: [PATCH 14/19] fs: Permit FIBMAP for users with CAP_SYS_RAWIO in
 s_user_ns

Heh, I was looking over http://www.gossamer-threads.com/lists/linux/kernel/103611
a little while ago :)  The same question was asked 16 years ago.  Apparently
the answer then was that it was easier than fixing the code.

Quoting Theodore Ts'o (tytso@....edu):
> 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@...onical.com):
> > > Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
> > 
> > Acked-by: Serge Hallyn <serge.hallyn@...onical.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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