[ 3.5.y.z extended stable ] Patch "tun: signedness bug in tun_get_user()" has been added to staging queue

[Luis Henriques]

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

    tun: signedness bug in tun_get_user()

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

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

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 49b661475c4a7f0ee0ffbf9a65d2dc3feb4d955f Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter at oracle.com>
Date: Thu, 15 Aug 2013 15:52:57 +0300
Subject: [PATCH] tun: signedness bug in tun_get_user()

commit 15718ea0d844e4816dbd95d57a8a0e3e264ba90e upstream.

The recent fix d9bf5f1309 "tun: compare with 0 instead of total_len" is
not totally correct.  Because "len" and "sizeof()" are size_t type, that
means they are never less than zero.

Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>
Acked-by: Neil Horman <nhorman at tuxdriver.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/tun.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 21c33f2..f21bcef 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -615,8 +615,9 @@ static ssize_t tun_get_user(struct tun_struct *tun,
 	int offset = 0;

 	if (!(tun->flags & TUN_NO_PI)) {
-		if ((len -= sizeof(pi)) > count)
+		if (len < sizeof(pi))
 			return -EINVAL;
+		len -= sizeof(pi);

 		if (memcpy_fromiovecend((void *)&pi, iv, 0, sizeof(pi)))
 			return -EFAULT;
@@ -624,8 +625,9 @@ static ssize_t tun_get_user(struct tun_struct *tun,
 	}

 	if (tun->flags & TUN_VNET_HDR) {
-		if ((len -= tun->vnet_hdr_sz) > count)
+		if (len < tun->vnet_hdr_sz)
 			return -EINVAL;
+		len -= tun->vnet_hdr_sz;

 		if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso)))
 			return -EFAULT;
--
1.8.3.2