[PATCH 3.2 008/149] tun: signedness bug in tun_get_user()

From: Ben Hutchings
Date: Mon Oct 21 2013 - 04:50:32 EST


3.2.52-rc1 review patch. If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ 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@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
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 f4c5de6..ee1aab0 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -614,8 +614,9 @@ 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;
@@ -623,8 +624,9 @@ 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;

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