[Asterisk-code-review] app_mixmonitor: cleanup datastore when monitor thread fails to launch (asterisk[master])

[George Joseph]

George Joseph has submitted this change. ( https://gerrit.asterisk.org/c/asterisk/+/15275 )

Change subject: app_mixmonitor: cleanup datastore when monitor thread fails to launch
......................................................................

app_mixmonitor: cleanup datastore when monitor thread fails to launch

launch_monitor_thread is responsible for creating and initializing
the mixmonitor, and dependent data structures. There was one off
nominal path after the datastore gets created that triggers when
the channel being monitored is hung up prior to monitor starting
itself.

If this happened the monitor thread would not "launch", and the
mixmonitor object and associated objects are freed, including the
underlying datastore data object. However, the datastore itself was
not removed from the channel, so when the channel eventually gets
destroyed it tries to access the previously freed datastore data
and crashes.

This patch removes and frees datastore object itself from the channel
before freeing the mixmonitor object thus ensuring the channel does
not call it when destroyed.

ASTERISK-28947 #close

Change-Id: Id4f9e958956d62473ed5ff06c98ae3436e839ff8
---
M apps/app_mixmonitor.c
1 file changed, 22 insertions(+), 1 deletion(-)

Approvals:
  Joshua Colp: Looks good to me, but someone else must approve
  Sean Bright: Looks good to me, but someone else must approve
  George Joseph: Looks good to me, approved; Approved for Submit



diff --git a/apps/app_mixmonitor.c b/apps/app_mixmonitor.c
index bb1bc51..239901f 100644
--- a/apps/app_mixmonitor.c
+++ b/apps/app_mixmonitor.c
@@ -865,6 +865,24 @@
 	return 0;
 }
 
+static void mixmonitor_ds_remove_and_free(struct ast_channel *chan, const char *datastore_id)
+{
+	struct ast_datastore *datastore;
+
+	ast_channel_lock(chan);
+
+	datastore = ast_channel_datastore_find(chan, &mixmonitor_ds_info, datastore_id);
+
+	/*
+	 * Currently the one place this function is called from guarantees a
+	 * datastore is present, thus return checks can be avoided here.
+	 */
+	ast_channel_datastore_remove(chan, datastore);
+	ast_datastore_free(datastore);
+
+	ast_channel_unlock(chan);
+}
+
 static int launch_monitor_thread(struct ast_channel *chan, const char *filename,
 				  unsigned int flags, int readvol, int writevol,
 				  const char *post_process, const char *filename_write,
@@ -940,7 +958,6 @@
 			pbx_builtin_setvar_helper(chan, uid_channel_var, datastore_id);
 		}
 	}
-	ast_free(datastore_id);
 
 	mixmonitor->name = ast_strdup(ast_channel_name(chan));
 
@@ -990,12 +1007,16 @@
 	if (startmon(chan, &mixmonitor->audiohook)) {
 		ast_log(LOG_WARNING, "Unable to add '%s' spy to channel '%s'\n",
 			mixmonitor_spy_type, ast_channel_name(chan));
+		mixmonitor_ds_remove_and_free(chan, datastore_id);
+		ast_free(datastore_id);
 		ast_autochan_destroy(mixmonitor->autochan);
 		ast_audiohook_destroy(&mixmonitor->audiohook);
 		mixmonitor_free(mixmonitor);
 		return -1;
 	}
 
+	ast_free(datastore_id);
+
 	/* reference be released at mixmonitor destruction */
 	mixmonitor->callid = ast_read_threadstorage_callid();
 

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Gerrit-Project: asterisk
Gerrit-Branch: master
Gerrit-Change-Id: Id4f9e958956d62473ed5ff06c98ae3436e839ff8
Gerrit-Change-Number: 15275
Gerrit-PatchSet: 3
Gerrit-Owner: Kevin Harwell <kharwell at digium.com>
Gerrit-Reviewer: Friendly Automation
Gerrit-Reviewer: George Joseph <gjoseph at digium.com>
Gerrit-Reviewer: Joshua Colp <jcolp at sangoma.com>
Gerrit-Reviewer: Sean Bright <sean.bright at gmail.com>
Gerrit-MessageType: merged
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