From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp2130.oracle.com ([156.151.31.86]:39238 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729291AbfDQTBd (ORCPT ); Wed, 17 Apr 2019 15:01:33 -0400 Date: Wed, 17 Apr 2019 12:01:24 -0700 From: "Darrick J. Wong" Subject: Re: [PATCH v2 4/4] xfs: don't allow most setxattr to immutable files Message-ID: <20190417190124.GA5057@magnolia> References: <155466882175.633834.15261194784129614735.stgit@magnolia> <155466884962.633834.14320700092446721044.stgit@magnolia> <20190409031929.GE5147@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Amir Goldstein Cc: Dave Chinner , linux-xfs , Linux MM , linux-fsdevel , Ext4 , Linux Btrfs On Tue, Apr 09, 2019 at 11:24:10AM +0300, Amir Goldstein wrote: > On Tue, Apr 9, 2019 at 6:19 AM Darrick J. Wong wrote: > > > > From: Darrick J. Wong > > > > The chattr manpage has this to say about immutable files: > > > > "A file with the 'i' attribute cannot be modified: it cannot be deleted > > or renamed, no link can be created to this file, most of the file's > > metadata can not be modified, and the file can not be opened in write > > mode." > > > > However, we don't actually check the immutable flag in the setattr code, > > which means that we can update project ids and extent size hints on > > supposedly immutable files. Therefore, reject a setattr call on an > > immutable file except for the case where we're trying to unset > > IMMUTABLE. > > > > Signed-off-by: Darrick J. Wong > > --- > > fs/xfs/xfs_ioctl.c | 46 ++++++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 44 insertions(+), 2 deletions(-) > > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > > index 5a1b96dad901..67d12027f563 100644 > > --- a/fs/xfs/xfs_ioctl.c > > +++ b/fs/xfs/xfs_ioctl.c > > @@ -1023,6 +1023,40 @@ xfs_ioctl_setattr_flush( > > return filemap_write_and_wait(inode->i_mapping); > > } > > > > +/* > > + * If immutable is set and we are not clearing it, we're not allowed to change > > + * anything else in the inode. > > This looks correct, but FYI, neither xfs_io nor chattr clears 'immutable' > and sets projid/*extsize in one ioctl/xfsctl, so there is no justification to > making an extra effort to support that use case. You could do with > checking 'immutable' inside xfs_ioctl_setattr_check_projid/*extsize() > and leave only the di_flags check here. However, the API does allow callers to clear immutable and set other fields in one go, so just because xfs_io won't do it doesn't mean we can ignore it. Then again I guess the manpage doesn't explicitly say what the behavior is supposed to be, so I guess we'll just ... argh, fine I'll go fix the manpage to document the behavior. --D > Some would say that will be cleaner code. > Its a matter of taste and its your subsystem, so feel free to dismiss > this comments. > > Thanks, > Amir. > > > Don't error out if we're only trying to set > > + * immutable on an immutable file. > > + */ > > +static int > > +xfs_ioctl_setattr_immutable( > > + struct xfs_inode *ip, > > + struct fsxattr *fa, > > + uint16_t di_flags, > > + uint64_t di_flags2) > > +{ > > + struct xfs_mount *mp = ip->i_mount; > > + > > + if (!(ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE) || > > + !(fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) > > + return 0; > > + > > + if ((ip->i_d.di_flags & ~XFS_DIFLAG_IMMUTABLE) != > > + (di_flags & ~XFS_DIFLAG_IMMUTABLE)) > > + return -EPERM; > > + if (ip->i_d.di_version >= 3 && ip->i_d.di_flags2 != di_flags2) > > + return -EPERM; > > + if (xfs_get_projid(ip) != fa->fsx_projid) > > + return -EPERM; > > + if (ip->i_d.di_extsize != fa->fsx_extsize >> mp->m_sb.sb_blocklog) > > + return -EPERM; > > + if (ip->i_d.di_version >= 3 && (di_flags2 & XFS_DIFLAG2_COWEXTSIZE) && > > + ip->i_d.di_cowextsize != fa->fsx_cowextsize >> mp->m_sb.sb_blocklog) > > + return -EPERM; > > + > > + return 0; > > +} > > + > > static int > > xfs_ioctl_setattr_xflags( > > struct xfs_trans *tp, > > @@ -1030,7 +1064,9 @@ xfs_ioctl_setattr_xflags( > > struct fsxattr *fa) > > { > > struct xfs_mount *mp = ip->i_mount; > > + uint16_t di_flags; > > uint64_t di_flags2; > > + int error; > > > > /* Can't change realtime flag if any extents are allocated. */ > > if ((ip->i_d.di_nextents || ip->i_delayed_blks) && > > @@ -1061,12 +1097,18 @@ xfs_ioctl_setattr_xflags( > > !capable(CAP_LINUX_IMMUTABLE)) > > return -EPERM; > > > > - /* diflags2 only valid for v3 inodes. */ > > + /* Don't allow changes to an immutable inode. */ > > + di_flags = xfs_flags2diflags(ip, fa->fsx_xflags); > > di_flags2 = xfs_flags2diflags2(ip, fa->fsx_xflags); > > + error = xfs_ioctl_setattr_immutable(ip, fa, di_flags, di_flags2); > > + if (error) > > + return error; > > + > > + /* diflags2 only valid for v3 inodes. */ > > if (di_flags2 && ip->i_d.di_version < 3) > > return -EINVAL; > > > > - ip->i_d.di_flags = xfs_flags2diflags(ip, fa->fsx_xflags); > > + ip->i_d.di_flags = di_flags; > > ip->i_d.di_flags2 = di_flags2; > > > > xfs_diflags_to_linux(ip);