[3.16.y-ckt stable] Patch "AIO: properly check iovec sizes" has been added to the 3.16.y-ckt tree

[Luis Henriques]

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

    AIO: properly check iovec sizes

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt26.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

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

>From 7db62c68a01a9c814df8783f7570e4549bec3566 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Date: Fri, 19 Feb 2016 17:36:21 -0800
Subject: AIO: properly check iovec sizes

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 at google.com>
Acked-by: Benjamin LaHaise <bcrl at kvack.org>
Tested-by: Willy Tarreau <w at 1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: Moritz Muehlenhoff <jmm at inutil.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/aio.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index a6f86dae34be..7aaa4164bba5 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1378,11 +1378,16 @@ 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;
 }