net: core: add getsockopt SO_PEERPIDFD

Add SO_PEERPIDFD which allows to get pidfd of peer socket holder pidfd.
This thing is direct analog of SO_PEERCRED which allows to get plain PID.

Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Kuniyuki Iwashima <[email protected]>
Cc: Lennart Poettering <[email protected]>
Cc: Luca Boccassi <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: Stanislav Fomichev <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Reviewed-by: Christian Brauner <[email protected]>
Acked-by: Stanislav Fomichev <[email protected]>
Tested-by: Luca Boccassi <[email protected]>
Signed-off-by: Alexander Mikhalitsyn <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

1 files changed, 16 insertions, 0 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index c46c2f5d860c..73c61a010b01 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -921,11 +921,26 @@ static void unix_unhash(struct sock *sk)
 	 */
 }
 
+static bool unix_bpf_bypass_getsockopt(int level, int optname)
+{
+	if (level == SOL_SOCKET) {
+		switch (optname) {
+		case SO_PEERPIDFD:
+			return true;
+		default:
+			return false;
+		}
+	}
+
+	return false;
+}
+
 struct proto unix_dgram_proto = {
 	.name			= "UNIX",
 	.owner			= THIS_MODULE,
 	.obj_size		= sizeof(struct unix_sock),
 	.close			= unix_close,
+	.bpf_bypass_getsockopt	= unix_bpf_bypass_getsockopt,
 #ifdef CONFIG_BPF_SYSCALL
 	.psock_update_sk_prot	= unix_dgram_bpf_update_proto,
 #endif
@@ -937,6 +952,7 @@ struct proto unix_stream_proto = {
 	.obj_size		= sizeof(struct unix_sock),
 	.close			= unix_close,
 	.unhash			= unix_unhash,
+	.bpf_bypass_getsockopt	= unix_bpf_bypass_getsockopt,
 #ifdef CONFIG_BPF_SYSCALL
 	.psock_update_sk_prot	= unix_stream_bpf_update_proto,
 #endif