ipv6: Fix potential uninit-value access in __ip6_make_skb()

commit 4e13d3a9c25b7080f8a619f961e943fe08c2672c upstream.

As it was done in commit fc1092f51567 ("ipv4: Fix uninit-value access in
__ip_make_skb()") for IPv4, check FLOWI_FLAG_KNOWN_NH on fl6->flowi6_flags
instead of testing HDRINCL on the socket to avoid a race condition which
causes uninit-value access.

Fixes: ea30388baebc ("ipv6: Fix an uninit variable access bug in __ip6_make_skb()")
Signed-off-by: Shigeru Yoshida <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Zhaoyang Li <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Shigeru Yoshida

net/ipv6/ip6_output.c

@@ -1985,7 +1985,8 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 		struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));
 		u8 icmp6_type;
 
-		if (sk->sk_socket->type == SOCK_RAW && !inet_sk(sk)->hdrincl)
+		if (sk->sk_socket->type == SOCK_RAW &&
+		    !(fl6->flowi6_flags & FLOWI_FLAG_KNOWN_NH))
 			icmp6_type = fl6->fl6_icmp_type;
 		else
 			icmp6_type = icmp6_hdr(skb)->icmp6_type;