3.5.7.22 -stable review patch.  If anyone has any objections, please let me 
know.

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

From: Dan Carpenter <[email protected]>

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 <[email protected]>
Acked-by: Michael S. Tsirkin <[email protected]>
Acked-by: Neil Horman <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <[email protected]>
---
 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

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