From: David Howells <dhowells@redhat.com>
Date: Mon, 7 Oct 2019 10:58:29 +0100
Subject: rxrpc: Fix trace-after-put looking at the put call record
Patch-mainline: v5.4-rc4
Git-commit: 48c9e0ec7cbbb7370448f859ccc8e3b7eb69e755
References: bsc#1154353

rxrpc_put_call() calls trace_rxrpc_call() after it has done the decrement
of the refcount - which looks at the debug_id in the call record.  But
unless the refcount was reduced to zero, we no longer have the right to
look in the record and, indeed, it may be deleted by some other thread.

Fix this by getting the debug_id out before decrementing the refcount and
then passing that into the tracepoint.

Fixes: e34d4234b0b7 ("rxrpc: Trace rxrpc_call usage")
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/trace/events/rxrpc.h |    6 +++---
 net/rxrpc/call_accept.c      |    2 +-
 net/rxrpc/call_object.c      |   28 +++++++++++++++++-----------
 3 files changed, 21 insertions(+), 15 deletions(-)

--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -606,10 +606,10 @@ TRACE_EVENT(rxrpc_client,
 	    );
 
 TRACE_EVENT(rxrpc_call,
-	    TP_PROTO(struct rxrpc_call *call, enum rxrpc_call_trace op,
+	    TP_PROTO(unsigned int call_debug_id, enum rxrpc_call_trace op,
 		     int usage, const void *where, const void *aux),
 
-	    TP_ARGS(call, op, usage, where, aux),
+	    TP_ARGS(call_debug_id, op, usage, where, aux),
 
 	    TP_STRUCT__entry(
 		    __field(unsigned int,		call		)
@@ -620,7 +620,7 @@ TRACE_EVENT(rxrpc_call,
 			     ),
 
 	    TP_fast_assign(
-		    __entry->call = call->debug_id;
+		    __entry->call = call_debug_id;
 		    __entry->op = op;
 		    __entry->usage = usage;
 		    __entry->where = where;
--- a/net/rxrpc/call_accept.c
+++ b/net/rxrpc/call_accept.c
@@ -97,7 +97,7 @@ static int rxrpc_service_prealloc_one(st
 	call->flags |= (1 << RXRPC_CALL_IS_SERVICE);
 	call->state = RXRPC_CALL_SERVER_PREALLOC;
 
-	trace_rxrpc_call(call, rxrpc_call_new_service,
+	trace_rxrpc_call(call->debug_id, rxrpc_call_new_service,
 			 atomic_read(&call->usage),
 			 here, (const void *)user_call_ID);
 
--- a/net/rxrpc/call_object.c
+++ b/net/rxrpc/call_object.c
@@ -240,7 +240,8 @@ struct rxrpc_call *rxrpc_new_client_call
 	if (p->intr)
 		__set_bit(RXRPC_CALL_IS_INTR, &call->flags);
 	call->tx_total_len = p->tx_total_len;
-	trace_rxrpc_call(call, rxrpc_call_new_client, atomic_read(&call->usage),
+	trace_rxrpc_call(call->debug_id, rxrpc_call_new_client,
+			 atomic_read(&call->usage),
 			 here, (const void *)p->user_call_ID);
 
 	/* We need to protect a partially set up call against the user as we
@@ -290,8 +291,8 @@ struct rxrpc_call *rxrpc_new_client_call
 	if (ret < 0)
 		goto error;
 
-	trace_rxrpc_call(call, rxrpc_call_connected, atomic_read(&call->usage),
-			 here, NULL);
+	trace_rxrpc_call(call->debug_id, rxrpc_call_connected,
+			 atomic_read(&call->usage), here, NULL);
 
 	rxrpc_start_call_timer(call);
 
@@ -313,8 +314,8 @@ error_dup_user_ID:
 error:
 	__rxrpc_set_call_completion(call, RXRPC_CALL_LOCAL_ERROR,
 				    RX_CALL_DEAD, ret);
-	trace_rxrpc_call(call, rxrpc_call_error, atomic_read(&call->usage),
-			 here, ERR_PTR(ret));
+	trace_rxrpc_call(call->debug_id, rxrpc_call_error,
+			 atomic_read(&call->usage), here, ERR_PTR(ret));
 	rxrpc_release_call(rx, call);
 	mutex_unlock(&call->user_mutex);
 	rxrpc_put_call(call, rxrpc_call_put);
@@ -376,7 +377,8 @@ bool rxrpc_queue_call(struct rxrpc_call
 	if (n == 0)
 		return false;
 	if (rxrpc_queue_work(&call->processor))
-		trace_rxrpc_call(call, rxrpc_call_queued, n + 1, here, NULL);
+		trace_rxrpc_call(call->debug_id, rxrpc_call_queued, n + 1,
+				 here, NULL);
 	else
 		rxrpc_put_call(call, rxrpc_call_put_noqueue);
 	return true;
@@ -391,7 +393,8 @@ bool __rxrpc_queue_call(struct rxrpc_cal
 	int n = atomic_read(&call->usage);
 	ASSERTCMP(n, >=, 1);
 	if (rxrpc_queue_work(&call->processor))
-		trace_rxrpc_call(call, rxrpc_call_queued_ref, n, here, NULL);
+		trace_rxrpc_call(call->debug_id, rxrpc_call_queued_ref, n,
+				 here, NULL);
 	else
 		rxrpc_put_call(call, rxrpc_call_put_noqueue);
 	return true;
@@ -406,7 +409,8 @@ void rxrpc_see_call(struct rxrpc_call *c
 	if (call) {
 		int n = atomic_read(&call->usage);
 
-		trace_rxrpc_call(call, rxrpc_call_seen, n, here, NULL);
+		trace_rxrpc_call(call->debug_id, rxrpc_call_seen, n,
+				 here, NULL);
 	}
 }
 
@@ -418,7 +422,7 @@ void rxrpc_get_call(struct rxrpc_call *c
 	const void *here = __builtin_return_address(0);
 	int n = atomic_inc_return(&call->usage);
 
-	trace_rxrpc_call(call, op, n, here, NULL);
+	trace_rxrpc_call(call->debug_id, op, n, here, NULL);
 }
 
 /*
@@ -445,7 +449,8 @@ void rxrpc_release_call(struct rxrpc_soc
 
 	_enter("{%d,%d}", call->debug_id, atomic_read(&call->usage));
 
-	trace_rxrpc_call(call, rxrpc_call_release, atomic_read(&call->usage),
+	trace_rxrpc_call(call->debug_id, rxrpc_call_release,
+			 atomic_read(&call->usage),
 			 here, (const void *)call->flags);
 
 	ASSERTCMP(call->state, ==, RXRPC_CALL_COMPLETE);
@@ -532,12 +537,13 @@ void rxrpc_put_call(struct rxrpc_call *c
 {
 	struct rxrpc_net *rxnet = call->rxnet;
 	const void *here = __builtin_return_address(0);
+	unsigned int debug_id = call->debug_id;
 	int n;
 
 	ASSERT(call != NULL);
 
 	n = atomic_dec_return(&call->usage);
-	trace_rxrpc_call(call, op, n, here, NULL);
+	trace_rxrpc_call(debug_id, op, n, here, NULL);
 	ASSERTCMP(n, >=, 0);
 	if (n == 0) {
 		_debug("call %d dead", call->debug_id);