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authorJason A. Donenfeld <Jason@zx2c4.com>2020-03-18 18:30:45 -0600
committerDavid S. Miller <davem@davemloft.net>2020-03-18 18:51:43 -0700
commita5588604af448664e796daf3c1d5a4523c60667b (patch)
treec46e3cd33a702ee79364d2272acaf51eeb526bf4 /drivers/net/wireguard/receive.c
parent551599edbfff2431cef943a772fbde1c3e26eaf8 (diff)
wireguard: queueing: account for skb->protocol==0
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> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/wireguard/receive.c')
-rw-r--r--drivers/net/wireguard/receive.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/net/wireguard/receive.c b/drivers/net/wireguard/receive.c
index 4a153894cee2..243ed7172dd2 100644
--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c
@@ -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)))