I'm just curious, under what circumstances would people set mtu to zero?
On 2/14/20 14:38, Eric Dumazet wrote:
If wireguard device mtu is set to zero, a divide by zero
crash happens in calculate_skb_padding().
This patch provides dev->min_mtu and dev->max_mtu bounds.
Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Reported-by: syzbot <syzkal...@googlegroups.com>
Cc: Jason A. Donenfeld <ja...@zx2c4.com>
Cc: wireguard@lists.zx2c4.com
---
drivers/net/wireguard/device.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/net/wireguard/device.c b/drivers/net/wireguard/device.c
index
43db442b1373073eaf5e805cfe6cfee15875437a..c02b84cca122d92ee8a81c5efdcf67aada2554d6
100644
--- a/drivers/net/wireguard/device.c
+++ b/drivers/net/wireguard/device.c
@@ -271,9 +271,14 @@ static void wg_setup(struct net_device *dev)
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->min_mtu = MESSAGE_PADDING_MULTIPLE;
+ dev->max_mtu = ETH_MAX_MTU - MESSAGE_MINIMUM_LENGTH -
+ sizeof(struct udphdr) -
+ max(sizeof(struct ipv6hdr), sizeof(struct iphdr));
SET_NETDEV_DEVTYPE(dev, &device_type);
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