ipv6: fix EFAULT on sendto with icmpv6 and hdrincl

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@6wind.com>
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/raw.c b/net/ipv6/raw.c
index af2f9a833c4e34d136e04cd7d4c3f8330fe1f07a..1bb88b4b677bc626f3f7fe524282790b03dae0e1 100644 (file)
--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -895,11 +895,14 @@ static int rawv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
        opt = ipv6_fixup_options(&opt_space, opt);
 
        fl6.flowi6_proto = proto;
-       rfv.msg = msg;
-       rfv.hlen = 0;
-       err = rawv6_probe_proto_opt(&rfv, &fl6);
-       if (err)
-               goto out;
+
+       if (!hdrincl) {
+               rfv.msg = msg;
+               rfv.hlen = 0;
+               err = rawv6_probe_proto_opt(&rfv, &fl6);
+               if (err)
+                       goto out;
+       }
 
        if (!ipv6_addr_any(daddr))
                fl6.daddr = *daddr;