[PATCH 3.12 053/181] aio: fix kernel memory disclosure in io_getevents() introduced in v3.10

Jiri Slaby
2014-06-30T12:15:57Z

From: Benjamin LaHaise <bcrl@kvack.org>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

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.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Petr Matousek <pmatouse@redhat.com>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
fs/aio.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index a0ed6c7d2cd2..829bda2b26d7 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1062,6 +1062,9 @@ static long aio_read_events_ring(struct kioctx *ctx,
if (head == tail)
goto out;

+ head %= ctx->nr_events;
+ tail %= ctx->nr_events;
+
while (ret < nr) {
long avail;
struct io_event *ev;
--
2.0.0