Re: CVE-2016-7097 causes acl leak
From: Mark Salyzyn
Date: Thu Dec 15 2016 - 10:22:36 EST
On 12/14/2016 03:30 PM, Greg KH wrote:
On Wed, Dec 14, 2016 at 12:20:50PM -0800, Mark Salyzyn wrote:
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.
Did I take the fix in 3.10-stable? What was the git commit id? Is 3.10
"broken" in this way? Is any other stable kernel broken?
I still don't have any idea of what is going on here...
greg k-h
Nothing is going on here, it is a heads up, eventually CVE's get
backported to stable as we do take them in through those paths. Telling
you to be aware that the original commit causes a leak, and my
experience has found that the leak affects these four file system drivers.
-- Mark