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

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Message-ID: <20161213111734.GD15362@quack2.suse.cz>
Date:   Tue, 13 Dec 2016 12:17:34 +0100
From:   Jan Kara <jack@...e.cz>
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 Mon 12-12-16 16:26:00, Mark Salyzyn wrote:
> On 12/11/2016 04:34 PM, Cong Wang wrote:
> >On Mon, Dec 5, 2016 at 9:16 AM, Mark Salyzyn <salyzyn@...roid.com> wrote:
> >>Commit 073931017b49d9458aa351605b43a7e34598caef has several occurrences of
> >>an acl leak.
> >>
> >>posix_acl_update_mode(inose, &mode, &acl);
> >>
> >>. . .
> >>
> >>posix_acl_release(acl);
> >>
> >>
> >>acl is NULLed in posix_acl_update_mode to signal caller to not update the
> >>acl; but because it is nulled, it is never released.
> >I think you blame the wrong commit, this leak exists before that commit.
> >Looks like we should just release it before NULL'ing.
> >
> >diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> >index 5955220..edd862a 100644
> >--- a/fs/posix_acl.c
> >+++ b/fs/posix_acl.c
> >@@ -648,8 +648,10 @@ int posix_acl_update_mode(struct inode *inode,
> >umode_t *mode_p,
> >         error = posix_acl_equiv_mode(*acl, &mode);
> >         if (error < 0)
> >                 return error;
> >-       if (error == 0)
> >+       if (error == 0) {
> >+               posix_acl_release(*acl);
> >                 *acl = NULL;
> >+       }
> >         if (!in_group_p(inode->i_gid) &&
> >             !capable_wrt_inode_uidgid(inode, CAP_FSETID))
> >                 mode &= ~S_ISGID;
> 
> The leaks were introduced in 9p, gfs2, jfs and xfs drivers only.

So I agree 9p leaks acl reference (and it was buggy even before my commit).
GFS2, JFS, and XFS seem to be OK as far as I can tell.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR