udp: introduce udp->udp_flags

According to syzbot, it is time to use proper atomic flags
for various UDP flags.

Add udp_flags field, and convert udp->corkflag to first
bit in it.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/linux/udp.h

@@ -32,14 +32,20 @@ static inline u32 udp_hashfn(const struct net *net, u32 num, u32 mask)
 	return (num + net_hash_mix(net)) & mask;
 }
 
+enum {
+	UDP_FLAGS_CORK,		/* Cork is required */
+};
+
 struct udp_sock {
 	/* inet_sock has to be the first member */
 	struct inet_sock inet;
 #define udp_port_hash		inet.sk.__sk_common.skc_u16hashes[0]
 #define udp_portaddr_hash	inet.sk.__sk_common.skc_u16hashes[1]
 #define udp_portaddr_node	inet.sk.__sk_common.skc_portaddr_node
+
+	unsigned long	 udp_flags;
+
 	int		 pending;	/* Any pending frames ? */
-	unsigned int	 corkflag;	/* Cork is required */
 	__u8		 encap_type;	/* Is this an Encapsulation socket? */
 	unsigned char	 no_check6_tx:1,/* Send zero UDP6 checksums on TX? */
 			 no_check6_rx:1,/* Allow zero UDP6 checksums on RX? */
@@ -51,6 +57,11 @@ struct udp_sock {
 			 gro_enabled:1,	/* Request GRO aggregation */
 			 accept_udp_l4:1,
 			 accept_udp_fraglist:1;
+/* indicator bits used by pcflag: */
+#define UDPLITE_BIT      0x1  		/* set by udplite proto init function */
+#define UDPLITE_SEND_CC  0x2  		/* set via udplite setsockopt         */
+#define UDPLITE_RECV_CC  0x4		/* set via udplite setsocktopt        */
+	__u8		 pcflag;        /* marks socket as UDP-Lite if > 0    */
 	/*
 	 * Following member retains the information to create a UDP header
 	 * when the socket is uncorked.
@@ -62,12 +73,6 @@ struct udp_sock {
 	 */
 	__u16		 pcslen;
 	__u16		 pcrlen;
-/* indicator bits used by pcflag: */
-#define UDPLITE_BIT      0x1  		/* set by udplite proto init function */
-#define UDPLITE_SEND_CC  0x2  		/* set via udplite setsockopt         */
-#define UDPLITE_RECV_CC  0x4		/* set via udplite setsocktopt        */
-	__u8		 pcflag;        /* marks socket as UDP-Lite if > 0    */
-	__u8		 unused[3];
 	/*
 	 * For encapsulation sockets.
 	 */
@@ -95,6 +100,15 @@ struct udp_sock {
 	int		forward_threshold;
 };
 
+#define udp_test_bit(nr, sk)			\
+	test_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags)
+#define udp_set_bit(nr, sk)			\
+	set_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags)
+#define udp_clear_bit(nr, sk)			\
+	clear_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags)
+#define udp_assign_bit(nr, sk, val)		\
+	assign_bit(UDP_FLAGS_##nr, &udp_sk(sk)->udp_flags, val)
+
 #define UDP_MAX_SEGMENTS	(1 << 6UL)
 
 #define udp_sk(ptr) container_of_const(ptr, struct udp_sock, inet.sk)

net/ipv4/udp.c

@@ -1051,7 +1051,7 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	u8 tos, scope;
 	__be16 dport;
 	int err, is_udplite = IS_UDPLITE(sk);
-	int corkreq = READ_ONCE(up->corkflag) || msg->msg_flags&MSG_MORE;
+	int corkreq = udp_test_bit(CORK, sk) || msg->msg_flags & MSG_MORE;
 	int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);
 	struct sk_buff *skb;
 	struct ip_options_data opt_copy;
@@ -1315,11 +1315,11 @@ void udp_splice_eof(struct socket *sock)
 	struct sock *sk = sock->sk;
 	struct udp_sock *up = udp_sk(sk);
 
-	if (!up->pending || READ_ONCE(up->corkflag))
+	if (!up->pending || udp_test_bit(CORK, sk))
 		return;
 
 	lock_sock(sk);
-	if (up->pending && !READ_ONCE(up->corkflag))
+	if (up->pending && !udp_test_bit(CORK, sk))
 		udp_push_pending_frames(sk);
 	release_sock(sk);
 }
@@ -2658,9 +2658,9 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 	switch (optname) {
 	case UDP_CORK:
 		if (val != 0) {
-			WRITE_ONCE(up->corkflag, 1);
+			udp_set_bit(CORK, sk);
 		} else {
-			WRITE_ONCE(up->corkflag, 0);
+			udp_clear_bit(CORK, sk);
 			lock_sock(sk);
 			push_pending_frames(sk);
 			release_sock(sk);
@@ -2783,7 +2783,7 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
 
 	switch (optname) {
 	case UDP_CORK:
-		val = READ_ONCE(up->corkflag);
+		val = udp_test_bit(CORK, sk);
 		break;
 
 	case UDP_ENCAP:

net/ipv6/udp.c

@@ -1332,7 +1332,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	int addr_len = msg->msg_namelen;
 	bool connected = false;
 	int ulen = len;
-	int corkreq = READ_ONCE(up->corkflag) || msg->msg_flags&MSG_MORE;
+	int corkreq = udp_test_bit(CORK, sk) || msg->msg_flags & MSG_MORE;
 	int err;
 	int is_udplite = IS_UDPLITE(sk);
 	int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);
@@ -1644,11 +1644,11 @@ static void udpv6_splice_eof(struct socket *sock)
 	struct sock *sk = sock->sk;
 	struct udp_sock *up = udp_sk(sk);
 
-	if (!up->pending || READ_ONCE(up->corkflag))
+	if (!up->pending || udp_test_bit(CORK, sk))
 		return;
 
 	lock_sock(sk);
-	if (up->pending && !READ_ONCE(up->corkflag))
+	if (up->pending && !udp_test_bit(CORK, sk))
 		udp_v6_push_pending_frames(sk);
 	release_sock(sk);
 }