[PATCH v1 net-next 4/7] af_unix: Move SOCK_PASS{CRED,PIDFD,SEC} to sk->sk_flags.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

As explained in the next patch, SO_PASSRIGHTS would have a problem
if we assigned a corresponding bit to socket->flags, so it must be
flagged on sk->sk_flags.

Mixing socket->flags and sk->sk_flags for similar options will look
confusing, and sk->sk_flags is unsigned long and has enough space.

Let's move SOCK_PASS{CRED,PIDFD,SEC} to sk->sk_flags.

While at it, BUILD_BUG_ON() is added in sock_set_flag(), and other
SOCK_XXX flags in net.h are grouped as enum.

Now, we can drop unix_sock_inherit_flags() and use sock_copy_flags()
instead to inherit flags from a listener to its embryo socket.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 include/linux/net.h | 15 +++++++--------
 include/net/sock.h  |  5 +++++
 net/core/scm.c      | 14 ++++++++------
 net/core/sock.c     | 12 ++++++------
 net/unix/af_unix.c  | 19 +++----------------
 5 files changed, 29 insertions(+), 36 deletions(-)

diff --git a/include/linux/net.h b/include/linux/net.h
index 0ff950eecc6b..f8418d6e33e0 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -36,14 +36,13 @@ struct net;
  * in sock->flags, but moved into sk->sk_wq->flags to be RCU protected.
  * Eventually all flags will be in sk->sk_wq->flags.
  */
-#define SOCKWQ_ASYNC_NOSPACE	0
-#define SOCKWQ_ASYNC_WAITDATA	1
-#define SOCK_NOSPACE		2
-#define SOCK_PASSCRED		3
-#define SOCK_PASSSEC		4
-#define SOCK_SUPPORT_ZC		5
-#define SOCK_CUSTOM_SOCKOPT	6
-#define SOCK_PASSPIDFD		7
+enum socket_flags {
+	SOCKWQ_ASYNC_NOSPACE,
+	SOCKWQ_ASYNC_WAITDATA,
+	SOCK_NOSPACE,
+	SOCK_SUPPORT_ZC,
+	SOCK_CUSTOM_SOCKOPT,
+};
 
 #ifndef ARCH_HAS_SOCKET_TYPES
 /**
diff --git a/include/net/sock.h b/include/net/sock.h
index f0fabb9fd28a..48b8856e2615 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -964,6 +964,10 @@ enum sock_flags {
 	SOCK_RCVMARK, /* Receive SO_MARK  ancillary data with packet */
 	SOCK_RCVPRIORITY, /* Receive SO_PRIORITY ancillary data with packet */
 	SOCK_TIMESTAMPING_ANY, /* Copy of sk_tsflags & TSFLAGS_ANY */
+	SOCK_PASSCRED, /* Receive SCM_CREDENTIALS ancillary data with packet */
+	SOCK_PASSPIDFD, /* Receive SCM_PIDFD ancillary data with packet */
+	SOCK_PASSSEC, /* Receive SCM_SECURITY ancillary data with packet */
+	SOCK_FLAG_MAX,
 };
 
 #define SK_FLAGS_TIMESTAMP ((1UL << SOCK_TIMESTAMP) | (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE))
@@ -981,6 +985,7 @@ static inline void sock_copy_flags(struct sock *nsk, const struct sock *osk)
 
 static inline void sock_set_flag(struct sock *sk, enum sock_flags flag)
 {
+	BUILD_BUG_ON(BYTES_TO_BITS(sizeof(sk->sk_flags)) <= SOCK_FLAG_MAX);
 	__set_bit(flag, &sk->sk_flags);
 }
 
diff --git a/net/core/scm.c b/net/core/scm.c
index 3f756f00e41e..4bf19f6303dd 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -411,7 +411,7 @@ static void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cooki
 	struct lsm_context ctx;
 	int err;
 
-	if (test_bit(SOCK_PASSSEC, &sock->flags)) {
+	if (sock_flag(sock->sk, SOCK_PASSSEC)) {
 		err = security_secid_to_secctx(scm->secid, &ctx);
 
 		if (err >= 0) {
@@ -425,7 +425,7 @@ static void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cooki
 
 static bool scm_has_secdata(struct socket *sock)
 {
-	return test_bit(SOCK_PASSSEC, &sock->flags);
+	return sock_flag(sock->sk, SOCK_PASSSEC);
 }
 #else
 static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
@@ -476,9 +476,11 @@ static void scm_pidfd_recv(struct msghdr *msg, struct scm_cookie *scm)
 static bool __scm_recv_common(struct socket *sock, struct msghdr *msg,
 			      struct scm_cookie *scm, int flags)
 {
+	struct sock *sk = sock->sk;
+
 	if (!msg->msg_control) {
-		if (test_bit(SOCK_PASSCRED, &sock->flags) ||
-		    test_bit(SOCK_PASSPIDFD, &sock->flags) ||
+		if (sock_flag(sk, SOCK_PASSCRED) ||
+		    sock_flag(sk, SOCK_PASSPIDFD) ||
 		    scm->fp || scm_has_secdata(sock))
 			msg->msg_flags |= MSG_CTRUNC;
 
@@ -486,7 +488,7 @@ static bool __scm_recv_common(struct socket *sock, struct msghdr *msg,
 		return false;
 	}
 
-	if (test_bit(SOCK_PASSCRED, &sock->flags)) {
+	if (sock_flag(sock->sk, SOCK_PASSCRED)) {
 		struct user_namespace *current_ns = current_user_ns();
 		struct ucred ucreds = {
 			.pid = scm->creds.pid,
@@ -521,7 +523,7 @@ void scm_recv_unix(struct socket *sock, struct msghdr *msg,
 	if (!__scm_recv_common(sock, msg, scm, flags))
 		return;
 
-	if (test_bit(SOCK_PASSPIDFD, &sock->flags))
+	if (sock_flag(sock->sk, SOCK_PASSPIDFD))
 		scm_pidfd_recv(msg, scm);
 
 	scm_destroy_cred(scm);
diff --git a/net/core/sock.c b/net/core/sock.c
index b64df2463300..a1720c7f9789 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1221,13 +1221,13 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
 		}
 		return -EPERM;
 	case SO_PASSSEC:
-		assign_bit(SOCK_PASSSEC, &sock->flags, valbool);
+		sock_valbool_flag(sk, SOCK_PASSSEC, valbool);
 		return 0;
 	case SO_PASSCRED:
-		assign_bit(SOCK_PASSCRED, &sock->flags, valbool);
+		sock_valbool_flag(sk, SOCK_PASSCRED, valbool);
 		return 0;
 	case SO_PASSPIDFD:
-		assign_bit(SOCK_PASSPIDFD, &sock->flags, valbool);
+		sock_valbool_flag(sk, SOCK_PASSPIDFD, valbool);
 		return 0;
 	case SO_TYPE:
 	case SO_PROTOCOL:
@@ -1853,11 +1853,11 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case SO_PASSCRED:
-		v.val = !!test_bit(SOCK_PASSCRED, &sock->flags);
+		v.val = sock_flag(sk, SOCK_PASSCRED);
 		break;
 
 	case SO_PASSPIDFD:
-		v.val = !!test_bit(SOCK_PASSPIDFD, &sock->flags);
+		v.val = sock_flag(sk, SOCK_PASSPIDFD);
 		break;
 
 	case SO_PEERCRED:
@@ -1954,7 +1954,7 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case SO_PASSSEC:
-		v.val = !!test_bit(SOCK_PASSSEC, &sock->flags);
+		v.val = sock_flag(sk, SOCK_PASSSEC);
 		break;
 
 	case SO_PEERSEC:
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index fa86e8c3aec5..e793e55f6c9b 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -767,10 +767,8 @@ static void copy_peercred(struct sock *sk, struct sock *peersk)
 
 static bool unix_passcred_enabled(const struct sock *sk)
 {
-	struct socket *sock = sk->sk_socket;
-
-	return test_bit(SOCK_PASSCRED, &sock->flags) ||
-		test_bit(SOCK_PASSPIDFD, &sock->flags);
+	return sock_flag(sk, SOCK_PASSCRED) ||
+		sock_flag(sk, SOCK_PASSPIDFD);
 }
 
 static int unix_listen(struct socket *sock, int backlog)
@@ -1713,17 +1711,6 @@ static int unix_socketpair(struct socket *socka, struct socket *sockb)
 	return 0;
 }
 
-static void unix_sock_inherit_flags(const struct socket *old,
-				    struct socket *new)
-{
-	if (test_bit(SOCK_PASSCRED, &old->flags))
-		set_bit(SOCK_PASSCRED, &new->flags);
-	if (test_bit(SOCK_PASSPIDFD, &old->flags))
-		set_bit(SOCK_PASSPIDFD, &new->flags);
-	if (test_bit(SOCK_PASSSEC, &old->flags))
-		set_bit(SOCK_PASSSEC, &new->flags);
-}
-
 static int unix_accept(struct socket *sock, struct socket *newsock,
 		       struct proto_accept_arg *arg)
 {
@@ -1760,7 +1747,7 @@ static int unix_accept(struct socket *sock, struct socket *newsock,
 	unix_state_lock(tsk);
 	unix_update_edges(unix_sk(tsk));
 	newsock->state = SS_CONNECTED;
-	unix_sock_inherit_flags(sock, newsock);
+	sock_copy_flags(tsk, sk);
 	sock_graft(tsk, newsock);
 	unix_state_unlock(tsk);
 	return 0;
-- 
2.49.0