| Message ID | 155379545404.24796.5019142212767521955.stgit@magnolia (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vfs: make immutable files actually immutable | expand |
On Thu, Mar 28, 2019 at 7:51 PM Darrick J. Wong <darrick.wong@oracle.com> wrote: > > From: Darrick J. Wong <darrick.wong@oracle.com> > > 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. > I think if preventing modification of projid and extent size hints is what you are after you should place the check in xfs_ioctl_setattr() and not in xfs_ioctl_setattr_xflags(). Yes, it sounds tempting to block changes of xfs_ioc_setxflags(), but it leads you to a trap of 2nd time chattr +i fails on -EPERM, because chattr(1) doesn't optimize out the SETFLAGS ioctl in the case of unmodified flags. I think if you try to fix that, code will get ugly, so I suggest that you let SETFLAGS slide. Thanks, Amir. > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> > --- > fs/xfs/xfs_ioctl.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > index 2bd1c5ab5008..9cf0bc0ae2bd 100644 > --- a/fs/xfs/xfs_ioctl.c > +++ b/fs/xfs/xfs_ioctl.c > @@ -1067,6 +1067,14 @@ xfs_ioctl_setattr_xflags( > !capable(CAP_LINUX_IMMUTABLE)) > return -EPERM; > > + /* > + * If immutable is set and we are not clearing it, we're not allowed > + * to change anything else in the inode. > + */ > + if ((ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE) && > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) > + return -EPERM; > + > /* diflags2 only valid for v3 inodes. */ > di_flags2 = xfs_flags2diflags2(ip, fa->fsx_xflags); > if (di_flags2 && ip->i_d.di_version < 3) >
On Thu, Mar 28, 2019 at 10:50:54AM -0700, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@oracle.com> > > 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 <darrick.wong@oracle.com> > --- > fs/xfs/xfs_ioctl.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > index 2bd1c5ab5008..9cf0bc0ae2bd 100644 > --- a/fs/xfs/xfs_ioctl.c > +++ b/fs/xfs/xfs_ioctl.c > @@ -1067,6 +1067,14 @@ xfs_ioctl_setattr_xflags( > !capable(CAP_LINUX_IMMUTABLE)) > return -EPERM; > > + /* > + * If immutable is set and we are not clearing it, we're not allowed > + * to change anything else in the inode. > + */ > + if ((ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE) && > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) > + return -EPERM; > + > /* diflags2 only valid for v3 inodes. */ > di_flags2 = xfs_flags2diflags2(ip, fa->fsx_xflags); > if (di_flags2 && ip->i_d.di_version < 3) Looks fine - catches both FS_IOC_SETFLAGS and FS_IOC_FSSETXATTR for XFS. Do the other filesystems that implement FS_IOC_FSSETXATTR have the same bug? Cheers, Dave.
On Fri, Mar 29, 2019 at 08:29:48AM +1100, Dave Chinner wrote: > On Thu, Mar 28, 2019 at 10:50:54AM -0700, Darrick J. Wong wrote: > > From: Darrick J. Wong <darrick.wong@oracle.com> > > > > 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 <darrick.wong@oracle.com> > > --- > > fs/xfs/xfs_ioctl.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > > > diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c > > index 2bd1c5ab5008..9cf0bc0ae2bd 100644 > > --- a/fs/xfs/xfs_ioctl.c > > +++ b/fs/xfs/xfs_ioctl.c > > @@ -1067,6 +1067,14 @@ xfs_ioctl_setattr_xflags( > > !capable(CAP_LINUX_IMMUTABLE)) > > return -EPERM; > > > > + /* > > + * If immutable is set and we are not clearing it, we're not allowed > > + * to change anything else in the inode. > > + */ > > + if ((ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE) && > > + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) > > + return -EPERM; > > + > > /* diflags2 only valid for v3 inodes. */ > > di_flags2 = xfs_flags2diflags2(ip, fa->fsx_xflags); > > if (di_flags2 && ip->i_d.di_version < 3) > > Looks fine - catches both FS_IOC_SETFLAGS and FS_IOC_FSSETXATTR > for XFS. > > Do the other filesystems that implement FS_IOC_FSSETXATTR have > the same bug? Yes. I'm not even 100% sure I've finished playing xfs whackamole yet. --D > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c index 2bd1c5ab5008..9cf0bc0ae2bd 100644 --- a/fs/xfs/xfs_ioctl.c +++ b/fs/xfs/xfs_ioctl.c @@ -1067,6 +1067,14 @@ xfs_ioctl_setattr_xflags( !capable(CAP_LINUX_IMMUTABLE)) return -EPERM; + /* + * If immutable is set and we are not clearing it, we're not allowed + * to change anything else in the inode. + */ + if ((ip->i_d.di_flags & XFS_DIFLAG_IMMUTABLE) && + (fa->fsx_xflags & FS_XFLAG_IMMUTABLE)) + return -EPERM; + /* diflags2 only valid for v3 inodes. */ di_flags2 = xfs_flags2diflags2(ip, fa->fsx_xflags); if (di_flags2 && ip->i_d.di_version < 3)