[3.11.y.z extended stable] Patch "aio: fix kernel memory disclosure in io_getevents() introduced in v3.10" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    aio: fix kernel memory disclosure in io_getevents() introduced in v3.10

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From aada2e8ea56c868a760a6501878fd4336ec0c178 Mon Sep 17 00:00:00 2001
From: Benjamin LaHaise <bcrl at kvack.org>
Date: Tue, 24 Jun 2014 13:32:51 -0400
Subject: aio: fix kernel memory disclosure in io_getevents() introduced in
 v3.10

commit edfbbf388f293d70bf4b7c0bc38774d05e6f711a upstream.

A kernel memory disclosure was introduced in aio_read_events_ring() in v3.10
by commit a31ad380bed817aa25f8830ad23e1a0480fef797.  The changes made to
aio_read_events_ring() failed to correctly limit the index into
ctx->ring_pages[], allowing an attacked to cause the subsequent kmap() of
an arbitrary page with a copy_to_user() to copy the contents into userspace.
This vulnerability has been assigned CVE-2014-0206.  Thanks to Mateusz and
Petr for disclosing this issue.

This patch applies to v3.12+.  A separate backport is needed for 3.10/3.11.

[jmoyer at redhat.com: backported to 3.10]
Signed-off-by: Benjamin LaHaise <bcrl at kvack.org>
Cc: Mateusz Guzik <mguzik at redhat.com>
Cc: Petr Matousek <pmatouse at redhat.com>
Cc: Kent Overstreet <kmo at daterainc.com>
Cc: Jeff Moyer <jmoyer at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/aio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index 48f02745b876..618021906aa9 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -719,6 +719,8 @@ static long aio_read_events_ring(struct kioctx *ctx,
 	if (head == ctx->tail)
 		goto out;

+	head %= ctx->nr_events;
+
 	while (ret < nr) {
 		long avail;
 		struct io_event *ev;
--
1.9.1