rxrpc: Call state should be read with READ_ONCE() under some circumstances

The call state may be changed at any time by the data-ready routine in
response to received packets, so if the call state is to be read and acted
upon several times in a function, READ_ONCE() must be used unless the call
state lock is held.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index 9f4cfa25af7c92c406e81d8003b8aa07c7892a04..d74921c4969b2d46d0096eca62853a68ae68c40f 100644 (file)
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -420,6 +420,7 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb,
                             u16 skew)
 {
        struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+       enum rxrpc_call_state state;
        unsigned int offset = sizeof(struct rxrpc_wire_header);
        unsigned int ix;
        rxrpc_serial_t serial = sp->hdr.serial, ack_serial = 0;
@@ -434,14 +435,15 @@ static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb,
        _proto("Rx DATA %%%u { #%u f=%02x }",
               sp->hdr.serial, seq, sp->hdr.flags);
 
-       if (call->state >= RXRPC_CALL_COMPLETE)
+       state = READ_ONCE(call->state);
+       if (state >= RXRPC_CALL_COMPLETE)
                return;
 
        /* Received data implicitly ACKs all of the request packets we sent
         * when we're acting as a client.
         */
-       if ((call->state == RXRPC_CALL_CLIENT_SEND_REQUEST ||
-            call->state == RXRPC_CALL_CLIENT_AWAIT_REPLY) &&
+       if ((state == RXRPC_CALL_CLIENT_SEND_REQUEST ||
+            state == RXRPC_CALL_CLIENT_AWAIT_REPLY) &&
            !rxrpc_receiving_reply(call))
                return;
 
@@ -799,7 +801,7 @@ static void rxrpc_input_ack(struct rxrpc_call *call, struct sk_buff *skb,
                return rxrpc_proto_abort("AK0", call, 0);
 
        /* Ignore ACKs unless we are or have just been transmitting. */
-       switch (call->state) {
+       switch (READ_ONCE(call->state)) {
        case RXRPC_CALL_CLIENT_SEND_REQUEST:
        case RXRPC_CALL_CLIENT_AWAIT_REPLY:
        case RXRPC_CALL_SERVER_SEND_REPLY:
@@ -940,7 +942,7 @@ static void rxrpc_input_call_packet(struct rxrpc_call *call,
 static void rxrpc_input_implicit_end_call(struct rxrpc_connection *conn,
                                          struct rxrpc_call *call)
 {
-       switch (call->state) {
+       switch (READ_ONCE(call->state)) {
        case RXRPC_CALL_SERVER_AWAIT_ACK:
                rxrpc_call_completed(call);
                break;

diff --git a/net/rxrpc/recvmsg.c b/net/rxrpc/recvmsg.c
index 6491ca46a03fda6dc66e02e887ad08012acca14b..3e2f1a8e9c5b51bf90ce8679c06b6ec8a8958ea9 100644 (file)
--- a/net/rxrpc/recvmsg.c
+++ b/net/rxrpc/recvmsg.c
@@ -527,7 +527,7 @@ try_again:
                msg->msg_namelen = len;
        }
 
-       switch (call->state) {
+       switch (READ_ONCE(call->state)) {
        case RXRPC_CALL_SERVER_ACCEPTING:
                ret = rxrpc_recvmsg_new_call(rx, call, msg, flags);
                break;
@@ -640,7 +640,7 @@ int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
 
        mutex_lock(&call->user_mutex);
 
-       switch (call->state) {
+       switch (READ_ONCE(call->state)) {
        case RXRPC_CALL_CLIENT_RECV_REPLY:
        case RXRPC_CALL_SERVER_RECV_REQUEST:
        case RXRPC_CALL_SERVER_ACK_REQUEST:

diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index bc2d3dcff9de76fcc42a20a3aeaec2305ebd2d6c..47ccfeacc1c6a247cc9dc37344f58f3198399049 100644 (file)
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -488,6 +488,7 @@ rxrpc_new_client_call_for_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg,
 int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
        __releases(&rx->sk.sk_lock.slock)
 {
+       enum rxrpc_call_state state;
        enum rxrpc_command cmd;
        struct rxrpc_call *call;
        unsigned long user_call_ID = 0;
@@ -526,13 +527,17 @@ int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
                        return PTR_ERR(call);
                /* ... and we have the call lock. */
        } else {
-               ret = -EBUSY;
-               if (call->state == RXRPC_CALL_UNINITIALISED ||
-                   call->state == RXRPC_CALL_CLIENT_AWAIT_CONN ||
-                   call->state == RXRPC_CALL_SERVER_PREALLOC ||
-                   call->state == RXRPC_CALL_SERVER_SECURING ||
-                   call->state == RXRPC_CALL_SERVER_ACCEPTING)
+               switch (READ_ONCE(call->state)) {
+               case RXRPC_CALL_UNINITIALISED:
+               case RXRPC_CALL_CLIENT_AWAIT_CONN:
+               case RXRPC_CALL_SERVER_PREALLOC:
+               case RXRPC_CALL_SERVER_SECURING:
+               case RXRPC_CALL_SERVER_ACCEPTING:
+                       ret = -EBUSY;
                        goto error_release_sock;
+               default:
+                       break;
+               }
 
                ret = mutex_lock_interruptible(&call->user_mutex);
                release_sock(&rx->sk);
@@ -542,10 +547,11 @@ int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
                }
        }
 
+       state = READ_ONCE(call->state);
        _debug("CALL %d USR %lx ST %d on CONN %p",
-              call->debug_id, call->user_call_ID, call->state, call->conn);
+              call->debug_id, call->user_call_ID, state, call->conn);
 
-       if (call->state >= RXRPC_CALL_COMPLETE) {
+       if (state >= RXRPC_CALL_COMPLETE) {
                /* it's too late for this call */
                ret = -ESHUTDOWN;
        } else if (cmd == RXRPC_CMD_SEND_ABORT) {
@@ -555,12 +561,12 @@ int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
        } else if (cmd != RXRPC_CMD_SEND_DATA) {
                ret = -EINVAL;
        } else if (rxrpc_is_client_call(call) &&
-                  call->state != RXRPC_CALL_CLIENT_SEND_REQUEST) {
+                  state != RXRPC_CALL_CLIENT_SEND_REQUEST) {
                /* request phase complete for this client call */
                ret = -EPROTO;
        } else if (rxrpc_is_service_call(call) &&
-                  call->state != RXRPC_CALL_SERVER_ACK_REQUEST &&
-                  call->state != RXRPC_CALL_SERVER_SEND_REPLY) {
+                  state != RXRPC_CALL_SERVER_ACK_REQUEST &&
+                  state != RXRPC_CALL_SERVER_SEND_REPLY) {
                /* Reply phase not begun or not complete for service call. */
                ret = -EPROTO;
        } else {
@@ -605,14 +611,20 @@ int rxrpc_kernel_send_data(struct socket *sock, struct rxrpc_call *call,
        _debug("CALL %d USR %lx ST %d on CONN %p",
               call->debug_id, call->user_call_ID, call->state, call->conn);
 
-       if (call->state >= RXRPC_CALL_COMPLETE) {
-               ret = -ESHUTDOWN; /* it's too late for this call */
-       } else if (call->state != RXRPC_CALL_CLIENT_SEND_REQUEST &&
-                  call->state != RXRPC_CALL_SERVER_ACK_REQUEST &&
-                  call->state != RXRPC_CALL_SERVER_SEND_REPLY) {
-               ret = -EPROTO; /* request phase complete for this client call */
-       } else {
+       switch (READ_ONCE(call->state)) {
+       case RXRPC_CALL_CLIENT_SEND_REQUEST:
+       case RXRPC_CALL_SERVER_ACK_REQUEST:
+       case RXRPC_CALL_SERVER_SEND_REPLY:
                ret = rxrpc_send_data(rxrpc_sk(sock->sk), call, msg, len);
+               break;
+       case RXRPC_CALL_COMPLETE:
+               /* It's too late for this call */
+               ret = -ESHUTDOWN;
+               break;
+       default:
+                /* Request phase complete for this client call */
+               ret = -EPROTO;
+               break;
        }
 
        mutex_unlock(&call->user_mutex);