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From 1b5282d8303177cebf8496656da1dada29517e9d Mon Sep 17 00:00:00 2001
From: Debarshi Ray <debarshir@freedesktop.org>
Date: Fri, 4 Dec 2020 02:17:48 +0100
Subject: [PATCH] Don't remove a queue more than once
Currently, the dleyna_task_processor_remove_queues_for_sink and
dleyna_task_processor_remove_queues_for_source APIs can corrupt the
memory of the hash table of queues in the processor.
These APIs iterate through the queues in the hash table using
g_hash_table_foreach_remove, and let the callbacks return TRUE when a
queue is to be removed. Unfortunately, the callbacks use prv_cancel,
which might have already removed the queue using g_hash_table_remove.
It happens specifically for queues that have no current_task and have
the DLEYNA_TASK_QUEUE_FLAG_AUTO_REMOVE flag set.
dleyna-renderer-service has such a queue, whose task_delete_cb handler
is set to dleyna_gasync_task_delete_cb. When dleyna-renderer-service
loses it's last D-Bus client, it first invokes
dleyna_task_processor_remove_queues_for_source, followed by
dleyna_task_processor_set_quitting. The former corrupts the hash
table. The latter invokes prv_cancel_all_queues, which again goes
through the hash table and tries to remove them. This leads to crashes
with backtraces containing dleyna_gasync_task_delete_cb, GPtrArray,
prv_task_cancel_and_free_cb, or similar code paths originating from
prv_cancel_only.
Here's an example:
%0 prv_task_cancel_and_free_cb (data=0x56246f2425f0,
user_data=<optimized out>)
at libdleyna/core/task-processor.c:180
%1 g_ptr_array_foreach (array=0x56246f68b5a0,
func=0x7f41d2335850 <prv_task_cancel_and_free_cb>,
user_data=0x56246f4ea1a0)
at ../glib/garray.c:2091
%2 prv_cancel_only (queue_id=<optimized out>,
task_queue=0x56246f4ea1a0)
at libdleyna/core/task-processor.c:193
%3 prv_cancel_cb (key=<optimized out>,
value=0x56246f4ea1a0,
user_data=<optimized out>)
at libdleyna/core/task-processor.c:229
%4 g_hash_table_foreach_remove_or_steal (hash_table=0x56246f1e82a0,
func=func@entry=0x7f41d2335c10 <prv_cancel_cb>,
user_data=user_data@entry=0x0,
notify=notify@entry=1)
at ../glib/ghash.c:1947
%5 g_hash_table_foreach_remove (hash_table=<optimized out>,
func=func@entry=0x7f41d2335c10 <prv_cancel_cb>,
user_data=user_data@entry=0x0)
at ../glib/ghash.c:1993
%6 prv_cancel_all_queues (processor=0x56246f1f3510)
at libdleyna/core/task-processor.c:244
%7 dleyna_task_processor_set_quitting (processor=0x56246f1f3510)
at libdleyna/core/task-processor.c:259
%8 prv_lost_client (connection=<optimized out>,
name=0x56246f24e5d0 ":1.47515",
user_data=<optimized out>)
at src/connector-dbus.c:283
%9 actually_do_call (call_type=CALL_TYPE_NAME_VANISHED,
name_owner=<optimized out>,
connection=<optimized out>,
client=0x56246f24efb0)
at ../gio/gdbusnamewatching.c:171
%10 actually_do_call (call_type=CALL_TYPE_NAME_VANISHED,
name_owner=<optimized out>,
connection=<optimized out>,
client=0x56246f24efb0)
at ../gio/gdbusnamewatching.c:149
%11 do_call (client=0x56246f24efb0, call_type=CALL_TYPE_NAME_VANISHED)
at ../gio/gdbusnamewatching.c:224
%12 call_vanished_handler (client=0x56246f24efb0)
at ../gio/gdbusnamewatching.c:249
%13 call_vanished_handler (client=0x56246f24efb0)
at ../gio/gdbusnamewatching.c:242
%14 on_name_owner_changed (connection=<optimized out>,
sender_name=0x56246f24a260 "org.freedesktop.DBus",
object_path=0x56246f7ad950 "/org/freedesktop/DBus",
interface_name=0x56246f27a2a0 "org.freedesktop.DBus",
signal_name=<optimized out>,
parameters=0x56246f21ee90, user_data=0x1)
at ../gio/gdbusnamewatching.c:352
%15 emit_signal_instance_in_idle_cb (data=data@entry=0x56246f236950)
at ../gio/gdbusconnection.c:3777
%16 g_idle_dispatch (source=source@entry=0x56246f7080a0,
callback=0x7f41d1e1e640 <emit_signal_instance_in_idle_cb>,
user_data=0x56246f236950)
at ../glib/gmain.c:5836
%17 g_main_dispatch (context=0x56246f1f2920) at ../glib/gmain.c:3325
%18 g_main_context_dispatch (context=0x56246f1f2920)
at ../glib/gmain.c:4043
%19 g_main_context_iterate.constprop.0 (context=0x56246f1f2920,
block=block@entry=1,
dispatch=dispatch@entry=1,
self=<optimized out>)
at ../glib/gmain.c:4119
%20 g_main_loop_run (loop=0x56246f2337a0) at ../glib/gmain.c:4317
%21 dleyna_main_loop_start (server=<optimized out>,
control_point=<optimized out>,
user_data=<optimized out>)
at libdleyna/core/main-loop.c:154
%22 __libc_start_main (main=0x56246d8b40d0 <main>,
argc=1,
argv=0x7ffd4b757768,
init=<optimized out>,
fini=<optimized out>,
rtld_fini=<optimized out>,
stack_end=0x7ffd4b757758)
at ../csu/libc-start.c:314
%23 _start ()
Looking at the innards of the task_queue, it's seen that all the
function pointers have the same value, which doesn't match with the
reality of the code and is indicative of a memory error:
(gdb) print *task_queue
$2 = {tasks = 0x56210d62385a,
task_process_cb = 0x9595959595959595,
task_cancel_cb = 0x9595959595959595,
task_delete_cb = 0x9595959595959595,
task_queue_finally_cb = 0x9595959595959595,
current_task = 0x9595959595959595,
idle_id = 2509608341,
defer_remove = -1785358955,
flags = 2509608341,
user_data = 0x9595959595959595,
cancelled = -1785358955}
Based on initial work done by Robert Tiemann.
https://bugzilla.redhat.com/show_bug.cgi?id=1903139
https://github.com/phako/dleyna-core/pull/1
---
libdleyna/core/task-processor.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/libdleyna/core/task-processor.c b/libdleyna/core/task-processor.c
index 39529a3dc967..f50dd569ed61 100644
--- a/libdleyna/core/task-processor.c
+++ b/libdleyna/core/task-processor.c
@@ -285,7 +285,7 @@ static gboolean prv_free_queue_for_source(gpointer key, gpointer value,
if (!strcmp(source, queue_key->source) && !queue->defer_remove) {
queue->defer_remove = (queue->current_task != NULL);
- prv_cancel(queue_key, queue);
+ prv_cancel_only(queue_key, queue);
if (!queue->defer_remove) {
DLEYNA_LOG_DEBUG("Removing queue <%s,%s>",
@@ -320,7 +320,7 @@ static gboolean prv_free_queue_for_sink(gpointer key, gpointer value,
if (!strcmp(sink, queue_key->sink) && !queue->defer_remove) {
queue->defer_remove = (queue->current_task != NULL);
- prv_cancel(queue_key, queue);
+ prv_cancel_only(queue_key, queue);
if (!queue->defer_remove) {
DLEYNA_LOG_DEBUG("Removing queue <%s,%s>",
--
2.28.0
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