1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
|
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Wed, 18 Mar 2020 18:30:45 -0600
Subject: [PATCH] wireguard: queueing: account for skb->protocol==0
commit a5588604af448664e796daf3c1d5a4523c60667b upstream.
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>
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(-)
--- a/drivers/net/wireguard/device.c
+++ b/drivers/net/wireguard/device.c
@@ -122,7 +122,7 @@ static netdev_tx_t wg_xmit(struct sk_buf
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;
--- a/drivers/net/wireguard/queueing.h
+++ b/drivers/net/wireguard/queueing.h
@@ -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_untr
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);
--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c
@@ -56,7 +56,7 @@ static int prepare_skb_header(struct sk_
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(
*/
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)))
|
