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From: Quan Zhou <quan@posteo.net>
To: wireguard@lists.zx2c4.com
Subject: Re: [PATCH net] wireguard: device: provide sane limits for mtu setting
Date: Fri, 14 Feb 2020 14:40:23 +0800
Message-ID: <ae2626ad-772e-985a-4cd0-90462269b978@posteo.net> (raw)
In-Reply-To: <20200214063814.229451-1-edumazet@google.com>

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 <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Cc: Jason A. Donenfeld <Jason@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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Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14  6:38 Eric Dumazet
2020-02-14  6:40 ` Quan Zhou [this message]
2020-02-14  7:11   ` Samir Nassar
2020-02-14 10:11     ` Quan Zhou
2020-02-14  9:11 ` Jason A. Donenfeld

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