linux-kernel - [PATCH 2/2] aio: fix kernel memory disclosure in io

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Message-ID: <edfbbf388f293d70bf4b7c0bc38774d05e6f711a.1403632276.git.bcrl@kvack.org>
Date:	Tue, 24 Jun 2014 14:02:17 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>, security@...nel.org
Cc:	linux-aio@...ck.org, linux-kernel@...r.kernel.org,
	Mateusz Guzik <mguzik@...hat.com>,
	Petr Matousek <pmatouse@...hat.com>,
	Kent Overstreet <kmo@...erainc.com>,
	Jeff Moyer <jmoyer@...hat.com>, stable@...r.kernel.org
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@...ck.org>
Cc: Mateusz Guzik <mguzik@...hat.com>
Cc: Petr Matousek <pmatouse@...hat.com>
Cc: Kent Overstreet <kmo@...erainc.com>
Cc: Jeff Moyer <jmoyer@...hat.com>
Cc: stable@...r.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


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