On Wed, Jan 30, 2019 at 09:42:19AM +0200, Amir Goldstein wrote:
> On Tue, Jan 29, 2019, 10:50 PM Vivek Goyal <vgoyal@xxxxxxxxxx wrote:
>
> > If a file has been copied up metadata only, and later data is copied up,
> > upper loses any security.capability xattr it has (underlying filesystem
> > clears it as upon file write).
> >
>
>
> Write also clears suid mode bits
> Should we restore these as well? Or do we already and I missed it?
[ Adding linux-unionfs ]
suid mode bit is only cleared if caller does not have CAP_FSETID.
should_remove_suid() {
if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
return kill;
}
We do copy up in the context of mounter which is root, often with
CAP_FSETID.
So while this is not a widespread problem yet, it is a potential issue.
We can fix it if somebody runs into it.
>
>
> > From a user's point of view, this is just a file copy-up and that should
> > not result in losing security.capability xattr. Hence, before data copy
> > up, save security.capability xattr (if any) and restore it on upper after
> > data copy up is complete.
> >
> > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> > ---
> > fs/overlayfs/copy_up.c | 24 +++++++++++++++++++++++-
> > fs/overlayfs/overlayfs.h | 1 +
> > fs/overlayfs/util.c | 44
> > ++++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 68 insertions(+), 1 deletion(-)
> >
> > Index: rhvgoyal-linux/fs/overlayfs/util.c
> > ===================================================================
> > --- rhvgoyal-linux.orig/fs/overlayfs/util.c 2019-01-28
> > 14:42:10.499670636 -0500
> > +++ rhvgoyal-linux/fs/overlayfs/util.c 2019-01-29 14:45:49.747395201 -0500
> > @@ -912,3 +912,47 @@ invalid:
> > res = -EINVAL;
> > goto err_free;
> > }
> > +
> > +size_t ovl_getxattr(struct dentry *dentry, char *name, void **value,
> > + size_t *size)
> > +{
> >
>
>
> Please add padding arg and use this helper from ovl_get_redirect_xattr.
Ok, will do.
Vivek
