[ Upstream commit 00ea1cee ]

If ip6_dst_lookup_tail has acquired a dst and fails the IPv4-mapped
check, release the dst before returning an error.

Fixes: ec5e3b0a ("ipv6: Inhibit IPv4-mapped src address on the wire.")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>