From cce2b0da954fb232cafc812ce5acd6f3b42341e9 Mon Sep 17 00:00:00 2001
From: Kevin Harwell <kharwell@digium.com>
Date: Mon, 27 Jan 2020 12:01:15 -0600
Subject: [PATCH] stasis/app: don't lock an app before a call to send
Calling 'app_send' eventually calls the app's message handler. It's possible
for a handler to obtain a lock on another object, and then need/want to lock
the app object. If the caller of 'app_send' locks the app object prior to
calling then there's a potential for a deadlock, if another thread calls
'app_send' without locking.
This patch makes it so 'app_send' is not called with the app object locked in
the section of code doing such.
ASTERISK-28423 #close
Change-Id: I6767c6d0933c7db1b984018966eefca4c0638a27
---
res/stasis/app.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/res/stasis/app.c b/res/stasis/app.c
index aba2661400..ee2fd0bc52 100644
--- a/res/stasis/app.c
+++ b/res/stasis/app.c
@@ -1126,8 +1126,23 @@ void app_update(struct stasis_app *app, stasis_app_cb handler, void *data)
"timestamp", ast_json_timeval(ast_tvnow(), NULL),
"application", app->name);
if (msg) {
+ /*
+ * The app must be unlocked before calling 'send' since a handler may
+ * subsequently attempt to grab the app lock after first obtaining a
+ * lock for another object, thus causing a deadlock.
+ */
+ ao2_unlock(app);
app_send(app, msg);
+ ao2_lock(app);
ast_json_unref(msg);
+ if (!app->handler) {
+ /*
+ * If the handler disappeared then the app was deactivated. In that
+ * case don't replace. Re-activation will reset the handler later.
+ */
+ ao2_unlock(app);
+ return;
+ }
}
} else {
ast_verb(1, "Activating Stasis app '%s'\n", app->name);
--
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