linux-kernel - Re: CVE-2016-7097 causes acl leak

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Date:   Tue, 13 Dec 2016 16:00:05 -0800
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mark Salyzyn <salyzyn@...roid.com>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        aneesh.kumar@...ux.vnet.ibm.com, Jan Kara <jack@...e.cz>
Subject: Re: CVE-2016-7097 causes acl leak

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@...roid.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