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

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Message-ID: <CAM_iQpUp2rFhsu+VZ_FN5RJyTA69mEbqvFju2+0O2VjeLKj5jg@mail.gmail.com>
Date:   Mon, 12 Dec 2016 22:26:09 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Mark Salyzyn <salyzyn@...roid.com>
Cc:     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, 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.