afs: Protect call->state changes against signals

Protect call->state changes against the call being prematurely terminated
due to a signal.

What can happen is that a signal causes afs_wait_for_call_to_complete() to
abort an afs_call because it's not yet complete whilst afs_deliver_to_call()
is delivering data to that call.

If the data delivery causes the state to change, this may overwrite the state
of the afs_call, making it not-yet-complete again - but no further
notifications will be forthcoming from AF_RXRPC as the rxrpc call has been
aborted and completed, so kAFS will just hang in various places waiting for
that call or on page bits that need clearing by that call.

A tracepoint to monitor call state changes is also provided.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 54 insertions, 46 deletions

diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
index bd44ae8b63d8..ea1460b9b71a 100644
--- a/fs/afs/rxrpc.c
+++ b/fs/afs/rxrpc.c
@@ -134,6 +134,7 @@ static struct afs_call *afs_alloc_call(struct afs_net *net,
 	atomic_set(&call->usage, 1);
 	INIT_WORK(&call->async_work, afs_process_async_call);
 	init_waitqueue_head(&call->waitq);
+	spin_lock_init(&call->state_lock);
 
 	o = atomic_inc_return(&net->nr_outstanding_calls);
 	trace_afs_call(call, afs_call_trace_alloc, 1, o,
@@ -288,8 +289,7 @@ static void afs_notify_end_request_tx(struct sock *sock,
 {
 	struct afs_call *call = (struct afs_call *)call_user_ID;
 
-	if (call->state == AFS_CALL_REQUESTING)
-		call->state = AFS_CALL_AWAIT_REPLY;
+	afs_set_call_state(call, AFS_CALL_CL_REQUESTING, AFS_CALL_CL_AWAIT_REPLY);
 }
 
 /*
@@ -444,82 +444,87 @@ error_kill_call:
  */
 static void afs_deliver_to_call(struct afs_call *call)
 {
-	u32 abort_code;
+	enum afs_call_state state;
+	u32 abort_code, remote_abort = 0;
 	int ret;
 
 	_enter("%s", call->type->name);
 
-	while (call->state == AFS_CALL_AWAIT_REPLY ||
-	       call->state == AFS_CALL_AWAIT_OP_ID ||
-	       call->state == AFS_CALL_AWAIT_REQUEST ||
-	       call->state == AFS_CALL_AWAIT_ACK
+	while (state = READ_ONCE(call->state),
+	       state == AFS_CALL_CL_AWAIT_REPLY ||
+	       state == AFS_CALL_SV_AWAIT_OP_ID ||
+	       state == AFS_CALL_SV_AWAIT_REQUEST ||
+	       state == AFS_CALL_SV_AWAIT_ACK
 	       ) {
-		if (call->state == AFS_CALL_AWAIT_ACK) {
+		if (state == AFS_CALL_SV_AWAIT_ACK) {
 			size_t offset = 0;
 			ret = rxrpc_kernel_recv_data(call->net->socket,
 						     call->rxcall,
 						     NULL, 0, &offset, false,
-						     &call->abort_code,
+						     &remote_abort,
 						     &call->service_id);
 			trace_afs_recv_data(call, 0, offset, false, ret);
 
 			if (ret == -EINPROGRESS || ret == -EAGAIN)
 				return;
-			if (ret < 0)
-				call->error = ret;
-			if (ret < 0 || ret == 1)
+			if (ret < 0 || ret == 1) {
+				if (ret == 1)
+					ret = 0;
 				goto call_complete;
+			}
 			return;
 		}
 
 		ret = call->type->deliver(call);
+		state = READ_ONCE(call->state);
 		switch (ret) {
 		case 0:
-			if (call->state == AFS_CALL_AWAIT_REPLY)
+			if (state == AFS_CALL_CL_PROC_REPLY)
 				goto call_complete;
+			ASSERTCMP(state, >, AFS_CALL_CL_PROC_REPLY);
 			goto done;
 		case -EINPROGRESS:
 		case -EAGAIN:
 			goto out;
+		case -EIO:
 		case -ECONNABORTED:
-			goto save_error;
+			ASSERTCMP(state, ==, AFS_CALL_COMPLETE);
+			goto done;
 		case -ENOTCONN:
 			abort_code = RX_CALL_DEAD;
 			rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
 						abort_code, ret, "KNC");
-			goto save_error;
+			goto local_abort;
 		case -ENOTSUPP:
 			abort_code = RXGEN_OPCODE;
 			rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
 						abort_code, ret, "KIV");
-			goto save_error;
+			goto local_abort;
 		case -ENODATA:
 		case -EBADMSG:
 		case -EMSGSIZE:
 		default:
 			abort_code = RXGEN_CC_UNMARSHAL;
-			if (call->state != AFS_CALL_AWAIT_REPLY)
+			if (state != AFS_CALL_CL_AWAIT_REPLY)
 				abort_code = RXGEN_SS_UNMARSHAL;
 			rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
 						abort_code, -EBADMSG, "KUM");
-			goto save_error;
+			goto local_abort;
 		}
 	}
 
 done:
-	if (call->state == AFS_CALL_COMPLETE && call->incoming)
+	if (state == AFS_CALL_COMPLETE && call->incoming)
 		afs_put_call(call);
 out:
 	_leave("");
 	return;
 
-save_error:
-	call->error = ret;
+local_abort:
+	abort_code = 0;
 call_complete:
-	if (call->state != AFS_CALL_COMPLETE) {
-		call->state = AFS_CALL_COMPLETE;
-		trace_afs_call_done(call);
-	}
+	afs_set_call_complete(call, ret, remote_abort);
+	state = AFS_CALL_COMPLETE;
 	goto done;
 }
 
@@ -551,14 +556,15 @@ static long afs_wait_for_call_to_complete(struct afs_call *call,
 		set_current_state(TASK_UNINTERRUPTIBLE);
 
 		/* deliver any messages that are in the queue */
-		if (call->state < AFS_CALL_COMPLETE && call->need_attention) {
+		if (!afs_check_call_state(call, AFS_CALL_COMPLETE) &&
+		    call->need_attention) {
 			call->need_attention = false;
 			__set_current_state(TASK_RUNNING);
 			afs_deliver_to_call(call);
 			continue;
 		}
 
-		if (call->state == AFS_CALL_COMPLETE)
+		if (afs_check_call_state(call, AFS_CALL_COMPLETE))
 			break;
 
 		life = rxrpc_kernel_check_life(call->net->socket, call->rxcall);
@@ -578,17 +584,17 @@ static long afs_wait_for_call_to_complete(struct afs_call *call,
 	__set_current_state(TASK_RUNNING);
 
 	/* Kill off the call if it's still live. */
-	if (call->state < AFS_CALL_COMPLETE) {
+	if (!afs_check_call_state(call, AFS_CALL_COMPLETE)) {
 		_debug("call interrupted");
 		if (rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
-					    RX_USER_ABORT, -EINTR, "KWI")) {
-			call->error = -ERESTARTSYS;
-			trace_afs_call_done(call);
-		}
+					    RX_USER_ABORT, -EINTR, "KWI"))
+			afs_set_call_complete(call, -EINTR, 0);
 	}
 
+	spin_lock_bh(&call->state_lock);
 	ac->abort_code = call->abort_code;
 	ac->error = call->error;
+	spin_unlock_bh(&call->state_lock);
 
 	ret = ac->error;
 	switch (ret) {
@@ -713,7 +719,7 @@ void afs_charge_preallocation(struct work_struct *work)
 				break;
 
 			call->async = true;
-			call->state = AFS_CALL_AWAIT_OP_ID;
+			call->state = AFS_CALL_SV_AWAIT_OP_ID;
 			init_waitqueue_head(&call->waitq);
 		}
 
@@ -769,7 +775,7 @@ static int afs_deliver_cm_op_id(struct afs_call *call)
 		return ret;
 
 	call->operation_ID = ntohl(call->tmp);
-	call->state = AFS_CALL_AWAIT_REQUEST;
+	afs_set_call_state(call, AFS_CALL_SV_AWAIT_OP_ID, AFS_CALL_SV_AWAIT_REQUEST);
 	call->offset = 0;
 
 	/* ask the cache manager to route the call (it'll change the call type
@@ -794,8 +800,7 @@ static void afs_notify_end_reply_tx(struct sock *sock,
 {
 	struct afs_call *call = (struct afs_call *)call_user_ID;
 
-	if (call->state == AFS_CALL_REPLYING)
-		call->state = AFS_CALL_AWAIT_ACK;
+	afs_set_call_state(call, AFS_CALL_SV_REPLYING, AFS_CALL_SV_AWAIT_ACK);
 }
 
 /*
@@ -879,6 +884,8 @@ int afs_extract_data(struct afs_call *call, void *buf, size_t count,
 		     bool want_more)
 {
 	struct afs_net *net = call->net;
+	enum afs_call_state state;
+	u32 remote_abort;
 	int ret;
 
 	_enter("{%s,%zu},,%zu,%d",
@@ -888,29 +895,30 @@ int afs_extract_data(struct afs_call *call, void *buf, size_t count,
 
 	ret = rxrpc_kernel_recv_data(net->socket, call->rxcall,
 				     buf, count, &call->offset,
-				     want_more, &call->abort_code,
+				     want_more, &remote_abort,
 				     &call->service_id);
 	trace_afs_recv_data(call, count, call->offset, want_more, ret);
 	if (ret == 0 || ret == -EAGAIN)
 		return ret;
 
+	state = READ_ONCE(call->state);
 	if (ret == 1) {
-		switch (call->state) {
-		case AFS_CALL_AWAIT_REPLY:
-			call->state = AFS_CALL_COMPLETE;
-			trace_afs_call_done(call);
+		switch (state) {
+		case AFS_CALL_CL_AWAIT_REPLY:
+			afs_set_call_state(call, state, AFS_CALL_CL_PROC_REPLY);
 			break;
-		case AFS_CALL_AWAIT_REQUEST:
-			call->state = AFS_CALL_REPLYING;
+		case AFS_CALL_SV_AWAIT_REQUEST:
+			afs_set_call_state(call, state, AFS_CALL_SV_REPLYING);
 			break;
+		case AFS_CALL_COMPLETE:
+			kdebug("prem complete %d", call->error);
+			return -EIO;
 		default:
 			break;
 		}
 		return 0;
 	}
 
-	call->error = ret;
-	call->state = AFS_CALL_COMPLETE;
-	trace_afs_call_done(call);
+	afs_set_call_complete(call, ret, remote_abort);
 	return ret;
 }