Re: CVE-2016-7097 causes acl leak

Greg KH
2016-12-14T00:00:13Z

On Tue, Dec 13, 2016 at 03:42:58PM -0800, Mark Salyzyn wrote:
> On 12/12/2016 10:26 PM, Cong Wang wrote:
> > On Mon, Dec 12, 2016 at 4:26 PM, Mark Salyzyn <salyzyn@android.com> wrote:
> > > The leaks were introduced in 9p, gfs2, jfs and xfs drivers only.
> >
> > Only the 9p case is obvious to me:
> >
> > diff --git a/fs/9p/acl.c b/fs/9p/acl.c
> > index b3c2cc7..082d227 100644
> > --- a/fs/9p/acl.c
> > +++ b/fs/9p/acl.c
> > @@ -277,6 +277,7 @@ static int v9fs_xattr_set_acl(const struct
> > xattr_handler *handler,
> > case ACL_TYPE_ACCESS:
> > if (acl) {
> > struct iattr iattr;
> > + struct posix_acl *old_acl = acl;
> >
> > retval = posix_acl_update_mode(inode,
> > &iattr.ia_mode, &acl);
> > if (retval)
> > @@ -287,6 +288,7 @@ static int v9fs_xattr_set_acl(const struct
> > xattr_handler *handler,
> > * by the mode bits. So don't
> > * update ACL.
> > */
> > + posix_acl_release(old_acl);
> > value = NULL;
> > size = 0;
> > }
> >
> >
> > The rest are anti-pattern (modifying parameters on stack via address)
> > but look correct.
>
> Greg KH: Beware that this similar fix needs to be applied to _backports_ to
> stable kernel trees on other filesystem driver that have the same pattern
> (with local posix_acl_release(acl) calls). I have found that depending on
> vintage these would include this driver 9p, and possibly gfs2, jfs and xfs.
> Be aware.

I don't understand what you mean here. What needs to be "backported" to
the stable tree? What commit in Linus's tree do I pick? If not a
commit there, where is it?

totally confused,

greg k-h