netdev - [PATCH v4 net-next 5/9] net: Restrict SO_PASS{CRED,PIDFD,SEC} to AF

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Message-ID: <20250515224946.6931-6-kuniyu@amazon.com>
Date: Thu, 15 May 2025 15:49:13 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Willem de Bruijn <willemb@...gle.com>
CC: Simon Horman <horms@...nel.org>, Christian Brauner <brauner@...nel.org>,
	Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
	<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v4 net-next 5/9] net: Restrict SO_PASS{CRED,PIDFD,SEC} to AF_{UNIX,NETLINK,BLUETOOTH}.

SCM_CREDENTIALS and SCM_SECURITY can be recv()ed by calling
scm_recv() or scm_recv_unix(), and SCM_PIDFD is only used by
scm_recv_unix().

scm_recv() is called from AF_NETLINK and AF_BLUETOOTH.

scm_recv_unix() is literally called from AF_UNIX.

Let's restrict SO_PASSCRED and SO_PASSSEC to such sockets and
SO_PASSPIDFD to AF_UNIX only.

Later, SOCK_PASS{CRED,PIDFD,SEC} will be moved to struct sock
and united with another field.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
---
v3:
  * Return -EOPNOTSUPP in getsockopt() too
  * Add CONFIG_SECURITY_NETWORK check for SO_PASSSEC
---
 include/net/sock.h | 14 +++++++++++++-
 net/core/sock.c    | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 3e15d7105ad2..56fa558d24c0 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2773,9 +2773,14 @@ static inline bool sk_is_udp(const struct sock *sk)
 	       sk->sk_protocol == IPPROTO_UDP;
 }
 
+static inline bool sk_is_unix(const struct sock *sk)
+{
+	return sk->sk_family == AF_UNIX;
+}
+
 static inline bool sk_is_stream_unix(const struct sock *sk)
 {
-	return sk->sk_family == AF_UNIX && sk->sk_type == SOCK_STREAM;
+	return sk_is_unix(sk) && sk->sk_type == SOCK_STREAM;
 }
 
 static inline bool sk_is_vsock(const struct sock *sk)
@@ -2783,6 +2788,13 @@ static inline bool sk_is_vsock(const struct sock *sk)
 	return sk->sk_family == AF_VSOCK;
 }
 
+static inline bool sk_may_scm_recv(const struct sock *sk)
+{
+	return (IS_ENABLED(CONFIG_UNIX) && sk->sk_family == AF_UNIX) ||
+		sk->sk_family == AF_NETLINK ||
+		(IS_ENABLED(CONFIG_BT) && sk->sk_family == AF_BLUETOOTH);
+}
+
 /**
  * sk_eat_skb - Release a skb if it is no longer needed
  * @sk: socket to eat this skb from
diff --git a/net/core/sock.c b/net/core/sock.c
index d7d6d3a8efe5..fd5f9d3873c1 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1221,12 +1221,21 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
 		}
 		return -EPERM;
 	case SO_PASSSEC:
+		if (!IS_ENABLED(CONFIG_SECURITY_NETWORK) || sk_may_scm_recv(sk))
+			return -EOPNOTSUPP;
+
 		assign_bit(SOCK_PASSSEC, &sock->flags, valbool);
 		return 0;
 	case SO_PASSCRED:
+		if (!sk_may_scm_recv(sk))
+			return -EOPNOTSUPP;
+
 		assign_bit(SOCK_PASSCRED, &sock->flags, valbool);
 		return 0;
 	case SO_PASSPIDFD:
+		if (!sk_is_unix(sk))
+			return -EOPNOTSUPP;
+
 		assign_bit(SOCK_PASSPIDFD, &sock->flags, valbool);
 		return 0;
 	case SO_TYPE:
@@ -1855,10 +1864,16 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case SO_PASSCRED:
+		if (!sk_may_scm_recv(sk))
+			return -EOPNOTSUPP;
+
 		v.val = !!test_bit(SOCK_PASSCRED, &sock->flags);
 		break;
 
 	case SO_PASSPIDFD:
+		if (!sk_is_unix(sk))
+			return -EOPNOTSUPP;
+
 		v.val = !!test_bit(SOCK_PASSPIDFD, &sock->flags);
 		break;
 
@@ -1956,6 +1971,9 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case SO_PASSSEC:
+		if (!IS_ENABLED(CONFIG_SECURITY_NETWORK) || !sk_may_scm_recv(sk))
+			return -EOPNOTSUPP;
+
 		v.val = !!test_bit(SOCK_PASSSEC, &sock->flags);
 		break;
 
-- 
2.49.0