On Thu, Mar 28, 2019 at 7:51 PM Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote: > > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > 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@xxxxxxxxxx> > --- > 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) >
