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Subject[PATCH 2/2] aio: fix kernel memory disclosure in io_getevents() introduced in v3.10
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
---
fs/aio.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index 6a9c7e4..955947e 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1063,6 +1063,9 @@ 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;
--
1.8.2.1

--
"Thought is the essence of where you are now."


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