Re: CVE-2016-7097 causes acl leak

[Mark Salyzyn]

On 12/13/2016 04:00 PM, Greg KH wrote:
> 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@xxxxxxxxxxx> 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

In 3.10-stable if you took the original CVE-2016-7097 fix it could break 
four file system drivers, the fix for each would 'look like' this one 
fix for the 9p driver.

-- Mark