rxrpc: Fix potential NULL-pointer exception

Fix a potential NULL-pointer exception in rxrpc_do_sendmsg().  The call
state check that I added should have gone into the else-body of the
if-statement where we actually have a call to check.

Found by CoverityScan CID#1414316 ("Dereference after null check").

Fixes: 8c55767f55a4 ("rxrpc: Fix deadlock between call creation and sendmsg/recvmsg")
Reported-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/rxrpc/sendmsg.c b/net/rxrpc/sendmsg.c
index 31c1538c1a8de69b8afe4335b9e5b263700ce980..27685d8cba1aefe1696712f03ad2ae513c9e3765 100644 (file)
--- a/net/rxrpc/sendmsg.c
+++ b/net/rxrpc/sendmsg.c
@@ -517,13 +517,6 @@ int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
                ret = -EBADSLT;
                if (cmd != RXRPC_CMD_SEND_DATA)
                        goto error_release_sock;
-               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)
-                       goto error_release_sock;
                call = rxrpc_new_client_call_for_sendmsg(rx, msg, user_call_ID,
                                                         exclusive);
                /* The socket is now unlocked... */
@@ -531,6 +524,14 @@ 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)
+                       goto error_release_sock;
+
                ret = mutex_lock_interruptible(&call->user_mutex);
                release_sock(&rx->sk);
                if (ret < 0) {