linux-kernel - [PATCH 3.19.y-ckt 01/70] [stable-only] AIO: properly check iovec sizes

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Date:	Wed, 16 Mar 2016 13:04:54 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Moritz Muehlenhoff <jmm@...til.org>,
	Luis Henriques <luis.henriques@...onical.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 01/70] [stable-only] AIO: properly check iovec sizes

v3.19.8-ckt17 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

In Linus's tree, the iovec code has been reworked massively, but in
older kernels the AIO layer should be checking this before passing the
request on to other layers.

Many thanks to Ben Hawkes of Google Project Zero for pointing out the
issue.

Reported-by: Ben Hawkes <hawkes@...gle.com>
Acked-by: Benjamin LaHaise <bcrl@...ck.org>
Tested-by: Willy Tarreau <w@....eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Moritz Muehlenhoff <jmm@...til.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 fs/aio.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index ebd0e9b..6a17d03 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1390,11 +1390,16 @@ static ssize_t aio_setup_single_vector(struct kiocb *kiocb,
 				       unsigned long *nr_segs,
 				       struct iovec *iovec)
 {
-	if (unlikely(!access_ok(!rw, buf, kiocb->ki_nbytes)))
+	size_t len = kiocb->ki_nbytes;
+
+	if (len > MAX_RW_COUNT)
+		len = MAX_RW_COUNT;
+
+	if (unlikely(!access_ok(!rw, buf, len)))
 		return -EFAULT;
 
 	iovec->iov_base = buf;
-	iovec->iov_len = kiocb->ki_nbytes;
+	iovec->iov_len = len;
 	*nr_segs = 1;
 	return 0;
 }
-- 
2.7.0