@@ -122,7 +122,7 @@ static netdev_tx_t wg_xmit(struct sk_buff *skb, struct net_device *dev)
u32 mtu;
int ret;
- if (unlikely(wg_skb_examine_untrusted_ip_hdr(skb) != skb->protocol)) {
+ if (unlikely(!wg_check_packet_protocol(skb))) {
ret = -EPROTONOSUPPORT;
net_dbg_ratelimited("%s: Invalid IP packet\n", dev->name);
goto err;
@@ -66,7 +66,7 @@ struct packet_cb {
#define PACKET_PEER(skb) (PACKET_CB(skb)->keypair->entry.peer)
/* Returns either the correct skb->protocol value, or 0 if invalid. */
-static inline __be16 wg_skb_examine_untrusted_ip_hdr(struct sk_buff *skb)
+static inline __be16 wg_examine_packet_protocol(struct sk_buff *skb)
{
if (skb_network_header(skb) >= skb->head &&
(skb_network_header(skb) + sizeof(struct iphdr)) <=
@@ -81,6 +81,12 @@ static inline __be16 wg_skb_examine_untrusted_ip_hdr(struct sk_buff *skb)
return 0;
}
+static inline bool wg_check_packet_protocol(struct sk_buff *skb)
+{
+ __be16 real_protocol = wg_examine_packet_protocol(skb);
+ return real_protocol && skb->protocol == real_protocol;
+}
+
static inline void wg_reset_packet(struct sk_buff *skb)
{
skb_scrub_packet(skb, true);
@@ -56,7 +56,7 @@ static int prepare_skb_header(struct sk_buff *skb, struct wg_device *wg)
size_t data_offset, data_len, header_len;
struct udphdr *udp;
- if (unlikely(wg_skb_examine_untrusted_ip_hdr(skb) != skb->protocol ||
+ if (unlikely(!wg_check_packet_protocol(skb) ||
skb_transport_header(skb) < skb->head ||
(skb_transport_header(skb) + sizeof(struct udphdr)) >
skb_tail_pointer(skb)))
@@ -388,7 +388,7 @@ static void wg_packet_consume_data_done(struct wg_peer *peer,
*/
skb->ip_summed = CHECKSUM_UNNECESSARY;
skb->csum_level = ~0; /* All levels */
- skb->protocol = wg_skb_examine_untrusted_ip_hdr(skb);
+ skb->protocol = wg_examine_packet_protocol(skb);
if (skb->protocol == htons(ETH_P_IP)) {
len = ntohs(ip_hdr(skb)->tot_len);
if (unlikely(len < sizeof(struct iphdr)))
We carry out checks to the effect of: if (skb->protocol != wg_examine_packet_protocol(skb)) goto err; By having wg_skb_examine_untrusted_ip_hdr return 0 on failure, this means that the check above still passes in the case where skb->protocol is zero, which is possible to hit with AF_PACKET: struct sockaddr_pkt saddr = { .spkt_device = "wg0" }; unsigned char buffer[5] = { 0 }; sendto(socket(AF_PACKET, SOCK_PACKET, /* skb->protocol = */ 0), buffer, sizeof(buffer), 0, (const struct sockaddr *)&saddr, sizeof(saddr)); Additional checks mean that this isn't actually a problem in the code base, but I could imagine it becoming a problem later if the function is used more liberally. I would prefer to fix this by having wg_examine_packet_protocol return a 32-bit ~0 value on failure, which will never match any value of skb->protocol, which would simply change the generated code from a mov to a movzx. However, sparse complains, and adding __force casts doesn't seem like a good idea, so instead we just add a simple helper function to check for the zero return value. Since wg_examine_packet_protocol itself gets inlined, this winds up not adding an additional branch to the generated code, since the 0 return value already happens in a mergable branch. Reported-by: Fabian Freyer <fabianfreyer@radicallyopensecurity.com> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- drivers/net/wireguard/device.c | 2 +- drivers/net/wireguard/queueing.h | 8 +++++++- drivers/net/wireguard/receive.c | 4 ++-- 3 files changed, 10 insertions(+), 4 deletions(-)