netdev - Re: [PATCH net 2/2] ipv6: fix EFAULT on sendto with icmpv6 and hdrincl

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Date:   Thu, 6 Jun 2019 13:52:49 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Olivier Matz <olivier.matz@...nd.com>, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>
Cc:     Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH net 2/2] ipv6: fix EFAULT on sendto with icmpv6 and
 hdrincl

Le 06/06/2019 à 09:15, Olivier Matz a écrit :
> The following code returns EFAULT (Bad address):
> 
>   s = socket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6);
>   setsockopt(s, SOL_IPV6, IPV6_HDRINCL, 1);
>   sendto(ipv6_icmp6_packet, addr);   /* returns -1, errno = EFAULT */
> 
> The IPv4 equivalent code works. A workaround is to use IPPROTO_RAW
> instead of IPPROTO_ICMPV6.
> 
> The failure happens because 2 bytes are eaten from the msghdr by
> rawv6_probe_proto_opt() starting from commit 19e3c66b52ca ("ipv6
> equivalent of "ipv4: Avoid reading user iov twice after
> raw_probe_proto_opt""), but at that time it was not a problem because
> IPV6_HDRINCL was not yet introduced.
> 
> Only eat these 2 bytes if hdrincl == 0.
> 
> Fixes: 715f504b1189 ("ipv6: add IPV6_HDRINCL option for raw sockets")
> Signed-off-by: Olivier Matz <olivier.matz@...nd.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>