From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: Sat, 20 Feb 2016 01:36:21 +0000 (-0800)
Subject: AIO: properly check iovec sizes
X-Git-Tag: v3.16.35~245
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=393d7444b291449373ff14138ec4cc5ab9042813;p=thirdparty%2Fkernel%2Fstable.git

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@google.com>
Acked-by: Benjamin LaHaise <bcrl@kvack.org>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Moritz Muehlenhoff <jmm@inutil.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---

diff --git a/fs/aio.c b/fs/aio.c
index a6f86dae34bec..7aaa4164bba59 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;
 }