inet: ping: check sock_net() in ping_get_port() and ping_lookup()

inet: ping: check sock_net() in ping_get_port() and ping_lookup()

We need to check socket netns before considering them in ping_get_port().
Otherwise, one malicious netns could 'consume' all ports.

Add corresponding check in ping_lookup().

Fixes: c319b4d76b9e ("net: ipv4: add IPPROTO_ICMP socket kind")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://patch.msgid.link/20250829153054.474201-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>