diff options
Diffstat (limited to 'target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-send-account-for-mtu-0-devices.patch')
| -rw-r--r-- | target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-send-account-for-mtu-0-devices.patch | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-send-account-for-mtu-0-devices.patch b/target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-send-account-for-mtu-0-devices.patch new file mode 100644 index 0000000000..d84efe20f0 --- /dev/null +++ b/target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-send-account-for-mtu-0-devices.patch @@ -0,0 +1,95 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: "Jason A. Donenfeld" <Jason@zx2c4.com> +Date: Fri, 14 Feb 2020 23:57:22 +0100 +Subject: [PATCH] wireguard: send: account for mtu=0 devices + +commit 175f1ca9a9ed8689d2028da1a7c624bb4fb4ff7e upstream. + +It turns out there's an easy way to get packets queued up while still +having an MTU of zero, and that's via persistent keep alive. This commit +makes sure that in whatever condition, we don't wind up dividing by +zero. Note that an MTU of zero for a wireguard interface is something +quasi-valid, so I don't think the correct fix is to limit it via +min_mtu. This can be reproduced easily with: + +ip link add wg0 type wireguard +ip link add wg1 type wireguard +ip link set wg0 up mtu 0 +ip link set wg1 up +wg set wg0 private-key <(wg genkey) +wg set wg1 listen-port 1 private-key <(wg genkey) peer $(wg show wg0 public-key) +wg set wg0 peer $(wg show wg1 public-key) persistent-keepalive 1 endpoint 127.0.0.1:1 + +However, while min_mtu=0 seems fine, it makes sense to restrict the +max_mtu. This commit also restricts the maximum MTU to the greatest +number for which rounding up to the padding multiple won't overflow a +signed integer. Packets this large were always rejected anyway +eventually, due to checks deeper in, but it seems more sound not to even +let the administrator configure something that won't work anyway. + +We use this opportunity to clean up this function a bit so that it's +clear which paths we're expecting. + +Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> +Cc: Eric Dumazet <eric.dumazet@gmail.com> +Reviewed-by: Eric Dumazet <edumazet@google.com> +Signed-off-by: David S. Miller <davem@davemloft.net> +Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> +--- + drivers/net/wireguard/device.c | 7 ++++--- + drivers/net/wireguard/send.c | 16 +++++++++++----- + 2 files changed, 15 insertions(+), 8 deletions(-) + +--- a/drivers/net/wireguard/device.c ++++ b/drivers/net/wireguard/device.c +@@ -258,6 +258,8 @@ static void wg_setup(struct net_device * + enum { WG_NETDEV_FEATURES = NETIF_F_HW_CSUM | NETIF_F_RXCSUM | + NETIF_F_SG | NETIF_F_GSO | + NETIF_F_GSO_SOFTWARE | NETIF_F_HIGHDMA }; ++ const int overhead = MESSAGE_MINIMUM_LENGTH + sizeof(struct udphdr) + ++ max(sizeof(struct ipv6hdr), sizeof(struct iphdr)); + + dev->netdev_ops = &netdev_ops; + dev->hard_header_len = 0; +@@ -271,9 +273,8 @@ static void wg_setup(struct net_device * + dev->features |= WG_NETDEV_FEATURES; + dev->hw_features |= WG_NETDEV_FEATURES; + dev->hw_enc_features |= WG_NETDEV_FEATURES; +- dev->mtu = ETH_DATA_LEN - MESSAGE_MINIMUM_LENGTH - +- sizeof(struct udphdr) - +- max(sizeof(struct ipv6hdr), sizeof(struct iphdr)); ++ dev->mtu = ETH_DATA_LEN - overhead; ++ dev->max_mtu = round_down(INT_MAX, MESSAGE_PADDING_MULTIPLE) - overhead; + + SET_NETDEV_DEVTYPE(dev, &device_type); + +--- a/drivers/net/wireguard/send.c ++++ b/drivers/net/wireguard/send.c +@@ -143,16 +143,22 @@ static void keep_key_fresh(struct wg_pee + + static unsigned int calculate_skb_padding(struct sk_buff *skb) + { ++ unsigned int padded_size, last_unit = skb->len; ++ ++ if (unlikely(!PACKET_CB(skb)->mtu)) ++ return ALIGN(last_unit, MESSAGE_PADDING_MULTIPLE) - last_unit; ++ + /* We do this modulo business with the MTU, just in case the networking + * layer gives us a packet that's bigger than the MTU. In that case, we + * wouldn't want the final subtraction to overflow in the case of the +- * padded_size being clamped. ++ * padded_size being clamped. Fortunately, that's very rarely the case, ++ * so we optimize for that not happening. + */ +- unsigned int last_unit = skb->len % PACKET_CB(skb)->mtu; +- unsigned int padded_size = ALIGN(last_unit, MESSAGE_PADDING_MULTIPLE); ++ if (unlikely(last_unit > PACKET_CB(skb)->mtu)) ++ last_unit %= PACKET_CB(skb)->mtu; + +- if (padded_size > PACKET_CB(skb)->mtu) +- padded_size = PACKET_CB(skb)->mtu; ++ padded_size = min(PACKET_CB(skb)->mtu, ++ ALIGN(last_unit, MESSAGE_PADDING_MULTIPLE)); + return padded_size - last_unit; + } + |