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Subject[PATCH 4.19 16/51] ipv6: fix EFAULT on sendto with icmpv6 and hdrincl
Date
From: Olivier Matz <olivier.matz@6wind.com>

[ Upstream commit b9aa52c4cb457e7416cc0c95f475e72ef4a61336 ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/raw.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

--- a/net/ipv6/raw.c
+++ b/net/ipv6/raw.c
@@ -894,11 +894,14 @@ static int rawv6_sendmsg(struct sock *sk
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;

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