From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 15 Aug 2013 12:52:57 +0000 (+0300)
Subject: tun: signedness bug in tun_get_user()
X-Git-Tag: v3.4.62~14
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=62d5a1d2a8a7c247c1f2dcd87b1e8c533b03017b;p=platform%2Fkernel%2Flinux-stable.git

tun: signedness bug in tun_get_user()

[ Upstream commit 15718ea0d844e4816dbd95d57a8a0e3e264ba90e ]

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@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index c896b8f..194f879 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;