net: Fix header size check for GSO case in recvmsg (af_packet)

[ Upstream commit 1f18b7176e2e41fada24584ce3c80e9abfaca52b]

Parameter 'len' is size_t type so it will never get negative.

Signed-off-by: Mariusz Kozlowski <mk@lab.zgora.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 2078a277e06b53f4e89181f8f4bb6bca21f7264a..e670cb21149186996ec0b0b367a6ee40ac90c797 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1595,9 +1595,11 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 
                err = -EINVAL;
                vnet_hdr_len = sizeof(vnet_hdr);
-               if ((len -= vnet_hdr_len) < 0)
+               if (len < vnet_hdr_len)
                        goto out_free;
 
+               len -= vnet_hdr_len;
+
                if (skb_is_gso(skb)) {
                        struct skb_shared_info *sinfo = skb_shinfo(skb);