Merge tag 'rxrpc-fixes-20200203' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

David Howells says:

====================
RxRPC fixes

Here are a number of fixes for AF_RXRPC:

 (1) Fix a potential use after free in rxrpc_put_local() where it was
     accessing the object just put to get tracing information.

 (2) Fix insufficient notifications being generated by the function that
     queues data packets on a call.  This occasionally causes recvmsg() to
     stall indefinitely.

 (3) Fix a number of packet-transmitting work functions to hold an active
     count on the local endpoint so that the UDP socket doesn't get
     destroyed whilst they're calling kernel_sendmsg() on it.

 (4) Fix a NULL pointer deref that stemmed from a call's connection pointer
     being cleared when the call was disconnected.

Changes:

 v2: Removed a couple of BUG() statements that got added.
====================

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 11 insertions, 12 deletions

diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 36587260cabd..a6c1349e965d 100644
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -364,11 +364,14 @@ void rxrpc_queue_local(struct rxrpc_local *local)
 void rxrpc_put_local(struct rxrpc_local *local)
 {
 	const void *here = __builtin_return_address(0);
+	unsigned int debug_id;
 	int n;
 
 	if (local) {
+		debug_id = local->debug_id;
+
 		n = atomic_dec_return(&local->usage);
-		trace_rxrpc_local(local->debug_id, rxrpc_local_put, n, here);
+		trace_rxrpc_local(debug_id, rxrpc_local_put, n, here);
 
 		if (n == 0)
 			call_rcu(&local->rcu, rxrpc_local_rcu);
@@ -380,14 +383,11 @@ void rxrpc_put_local(struct rxrpc_local *local)
  */
 struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local)
 {
-	unsigned int au;
-
 	local = rxrpc_get_local_maybe(local);
 	if (!local)
 		return NULL;
 
-	au = atomic_fetch_add_unless(&local->active_users, 1, 0);
-	if (au == 0) {
+	if (!__rxrpc_use_local(local)) {
 		rxrpc_put_local(local);
 		return NULL;
 	}
@@ -401,14 +401,11 @@ struct rxrpc_local *rxrpc_use_local(struct rxrpc_local *local)
  */
 void rxrpc_unuse_local(struct rxrpc_local *local)
 {
-	unsigned int au;
-
 	if (local) {
-		au = atomic_dec_return(&local->active_users);
-		if (au == 0)
+		if (__rxrpc_unuse_local(local)) {
+			rxrpc_get_local(local);
 			rxrpc_queue_local(local);
-		else
-			rxrpc_put_local(local);
+		}
 	}
 }
 
@@ -465,7 +462,7 @@ static void rxrpc_local_processor(struct work_struct *work)
 
 	do {
 		again = false;
-		if (atomic_read(&local->active_users) == 0) {
+		if (!__rxrpc_use_local(local)) {
 			rxrpc_local_destroyer(local);
 			break;
 		}
@@ -479,6 +476,8 @@ static void rxrpc_local_processor(struct work_struct *work)
 			rxrpc_process_local_events(local);
 			again = true;
 		}
+
+		__rxrpc_unuse_local(local);
 	} while (again);
 
 	rxrpc_put_local(local);