diff options
| author | Jason A. Donenfeld <Jason@zx2c4.com> | 2020-03-18 18:30:45 -0600 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2020-03-18 18:51:43 -0700 |
| commit | a5588604af448664e796daf3c1d5a4523c60667b (patch) | |
| tree | c46e3cd33a702ee79364d2272acaf51eeb526bf4 /drivers/net/wireguard/receive.c | |
| parent | 551599edbfff2431cef943a772fbde1c3e26eaf8 (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.c | 4 |
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))) |