From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay1.corp.sgi.com [137.38.102.111]) by oss.sgi.com (Postfix) with ESMTP id A86A77F95 for ; Thu, 29 Jan 2015 21:04:24 -0600 (CST) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay1.corp.sgi.com (Postfix) with ESMTP id 878388F80BB for ; Thu, 29 Jan 2015 19:04:21 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id biNBYuCtuld9xfu4 (version=TLSv1 cipher=AES256-SHA bits=256 verify=NO) for ; Thu, 29 Jan 2015 19:04:20 -0800 (PST) Date: Thu, 29 Jan 2015 22:04:11 -0500 From: Brian Foster Subject: Re: [PATCH 6/9] xfs: XFS_IOCTL_SETXATTR can run in user namespaces Message-ID: <20150130030411.GA22916@bfoster.bfoster> References: <1422328486-24661-1-git-send-email-david@fromorbit.com> <1422328486-24661-7-git-send-email-david@fromorbit.com> <20150129153515.GF17652@laptop.bfoster> <20150129235315.GG6282@dastard> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20150129235315.GG6282@dastard> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: iustin@k1024.org, xfs@oss.sgi.com On Fri, Jan 30, 2015 at 10:53:15AM +1100, Dave Chinner wrote: > On Thu, Jan 29, 2015 at 10:35:15AM -0500, Brian Foster wrote: > > On Tue, Jan 27, 2015 at 02:14:43PM +1100, Dave Chinner wrote: > > > From: Dave Chinner > > > > > > Currently XFS_IOCTL_SETXATTR will fail if run in a user namespace as > > > it it not allowed to change project IDs. The current code, however, > > > also prevents any other change being made as well, so things like > > > extent size hints cannot be set in user namespaces. This is wrong, > > > so only disallow access to project IDs and related flags from inside > > > the init namespace. > > > > > > Signed-off-by: Dave Chinner > > > --- > > > fs/xfs/xfs_ioctl.c | 22 +++++++++++++--------- > > > 1 file changed, 13 insertions(+), 9 deletions(-) > > > > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > > > index 563d2b4..ae6e1e3 100644 > > > --- a/fs/xfs/xfs_ioctl.c > > > +++ b/fs/xfs/xfs_ioctl.c > > > @@ -1120,6 +1120,19 @@ xfs_ioctl_setattr( > > > return -EINVAL; > > > > > > /* > > > + * Project Quota ID state is only allowed to change from within the init > > > + * namespace. Enforce that restriction only if we are trying to change > > > + * the quota ID state. Everything else is allowed in user namespaces. > > > + */ > > > + if (current_user_ns() != &init_user_ns) { > > > + if (xfs_get_projid(ip) != fa->fsx_projid) > > > + return -EINVAL; > > > + if ((fa->fsx_xflags & XFS_XFLAG_PROJINHERIT) ^ > > > + (ip->i_d.di_flags & XFS_DIFLAG_PROJINHERIT)) > > > > Why not use != here? Looks fine, anyways: > > Because ^ has an implicit cast of the variables to boolean (i.e flag > set or not), whereas != will only work if XFS_XFLAG_PROJINHERIT = > XFS_DIFLAG_PROJINHERIT. Given that the moment we add more DIFLAGs to > the xfs inode, the current "XFLAG value must match DIFLAG value" > rule is going to be broken, I think that logical evaluation is a > much safer practice for these types of comparisons. > Hrm, I'm not following how a boolean cast occurs here. Isn't ^ a bitwise operation? If I tweak the DIFLAG_PROJINHERIT to bit 15 (rather than 9) and regenerate assembly for the code above, I end up with something like this: /* -EINVAL */ movl $-22, %eax #, D.54727 ... /* load up the flags vars */ movzwl 354(%rdi), %ecx # ip_5(D)->i_d.di_flags,ip_5(D)->i_d.di_flags movl (%rsi), %edx # fa_3(D)->fsx_xflags, D.54728 ... /* grab the associated bits and cmp */ andl $512, %edx #, D.54728 andl $32768, %ecx #, D.54728 cmpl %edx, %ecx # D.54728, D.54728 /* ret 0 if values are equal */ movl $0, %edx #, tmp99 cmove %edx, %eax # tmp99,, D.54727 ret So it seems like this breaks just the same if the bit meaning doesn't match between fields..? Brian > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs