From 3dc036fb5045fc068c6abfbe4e62d0871d7ca82a Mon Sep 17 00:00:00 2001
From: xinpeng wang <wangxinpeng@uniontech.com>
Date: Tue, 18 Jun 2024 16:58:17 +0800
Subject: [PATCH] udiskslinuxmanager:use dbus interface after free

In handle_get_block_devices, call get_block_objects to obtain iface_block_device
of all current UDisksLinuxBlockObject, and then obtain the corresponding
UDisksLinuxBlockObject's object_path through iface_block_device.iface_block_device
is a GDBusInterfaceSkeleton, which saves the object through
g_dbus_interface_skeleton_set_object. g_object_add_weak_pointer is used here. This
function is not thread-safe.At this time, if other threads are releasing the object,
the program will crash.
This scene can be reproduced by quickly plugging and unplugging the USB disk.
The core is as follows (the redundant stack is omitted):
When accessing object in thread 1, the object is released by thread 2
info threads
   Id Target Id Frame
* 1 Thread 0x7f80979e70 (LWP 24559) 0x0000007f8a48dda0 in
g_dbus_object_get_object_path (object=0x0) at ../../../gio/gdbusobject.c:109
  2 Thread 0x7f88a43010 (LWP 1159) 0x0000007f8a0a6ae8 in __GI___libc_free
(mem=0x556a919c80) at malloc.c:3093

thread 1
(gdb) bt
0 0x0000007f8a48dda0 in g_dbus_object_get_object_path (object=0x0) at
../../../gio/gdbusobject.c:109
1 0x000000556a56911c in handle_get_block_devices (object=0x7f7c007ed0, invocation=
0x7f74016f20 [GDBusMethodInvocation], arg_options=<optimized out>)
     at udiskslinuxmanager.c:1063

(gdb) p ((GObject*)(blocks_p->data))->ref_count
$3 = 1
(gdb) p *((GDBusInterfaceSkeleton*)(blocks_p->data))
$6 = {parent_instance = {g_type_instance = {g_class = 0x556a64e740
[g_type: UDisksLinuxBlock/UDisksBlockSkeleton/GDBusInterfaceSkeleton]}, ref_count = 1,
qdata = 0x0},  priv = 0x7f7c004ac0}
(gdb) p *((GDBusInterfaceSkeleton*)(blocks_p->data))->priv
$7 = {lock = {p = 0x0, i = {0, 0}}, object = 0x0,
flags = G_DBUS_INTERFACE_SKELETON_FLAGS_HANDLE_METHOD_INVOCATIONS_IN_THREAD,
connections = 0x0, object_path = 0x0, hooked_vtable = 0x556a62b9f0}

thread 2
(gdb) bt
0 0x0000007f8a0a6ae8 in __GI___libc_free (mem=0x556a919c80) at malloc.c:3093
1 0x0000007f89ff1224 in () at /lib/aarch64-linux-gnu/libudev.so.1
2 0x0000007f89ff1348 in () at /lib/aarch64-linux-gnu/libudev.so.1
3 0x0000007f89ff5520 in () at /lib/aarch64-linux-gnu/libudev.so.1
4 0x0000007f89fff878 in udev_device_unref () at /lib/aarch64-linux-gnu/libudev.so.1
5 0x0000007f8a7aeb74 in () at /lib/aarch64-linux-gnu/libgudev-1.0.so.0
6 0x0000007f8a3193f8 in g_object_unref (_object=<optimized out>) at
../../../gobject/gobject.c:3346
7 0x0000007f8a3193f8 in g_object_unref (_object=0x7f680038a0) at
../../../gobject/gobject.c:3238
8 0x000000556a57700c in udisks_linux_device_finalize (object=0x7f5c005730
[UDisksLinuxDevice]) at udiskslinuxdevice.c:75
9 0x0000007f8a3193f8 in g_object_unref (_object=<optimized out>) at
../../../gobject/gobject.c:3346
10 0x0000007f8a3193f8 in g_object_unref (_object=0x7f5c005730) at
../../../gobject/gobject.c:3238
11 0x000000556a55d0fc in udisks_linux_drive_object_uevent
     (object=object@entry=0x556a5df370 [UDisksLinuxDriveObject],
action=action@entry=0x556a87b120
"remove",device=device@entry=0x7f74007610 [UDisksLinuxDevice])
     at udiskslinuxdriveobject.c:715
12 0x000000556a54840c in handle_block_uevent_for_drive
     (provider=provider@entry=0x556a5c8200 [UDisksLinuxProvider],
action=action@entry=0x556a87b120 "remove",device=device@entry=0x7f74007610
[UDisksLinuxDevice]) at udiskslinuxprovider.c:1035
13 0x000000556a548ab8 in handle_block_uevent (device=0x7f74007610 [UDisksLinuxDevice],
action=0x556a87b120 "remove", provider=0x556a5c8200 [UDisksLinuxProvider]) at
udiskslinuxprovider.c:1349
14 0x000000556a548ab8 in udisks_linux_provider_handle_uevent
     (provider=0x556a5c8200 [UDisksLinuxProvider], action=0x556a87b120 "remove",
device=0x7f74007610 [UDisksLinuxDevice]) at udiskslinuxprovider.c:1399
15 0x000000556a548cac in on_idle_with_probed_uevent (user_data=0x556a7e65a0) at
udiskslinuxprovider.c:230
---
 src/udiskslinuxmanager.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/udiskslinuxmanager.c b/src/udiskslinuxmanager.c
index 7a614f4..950dee2 100644
--- a/src/udiskslinuxmanager.c
+++ b/src/udiskslinuxmanager.c
@@ -1165,8 +1165,11 @@ handle_get_block_devices (UDisksManager         *object,
   blocks = get_block_objects (object, &num_blocks);
   block_paths = g_new0 (const gchar *, num_blocks + 1);
 
-  for (i = 0,blocks_p = blocks; blocks_p != NULL; blocks_p = blocks_p->next, i++)
-      block_paths[i] = g_dbus_object_get_object_path (g_dbus_interface_get_object (G_DBUS_INTERFACE (blocks_p->data)));
+  for (blocks_p = blocks; blocks_p != NULL; blocks_p = blocks_p->next) {
+	  GDBusObject * block_object = g_dbus_interface_get_object (G_DBUS_INTERFACE (blocks_p->data));
+	  if (block_object)
+		  block_paths[i++] = g_dbus_object_get_object_path (block_object);
+  }
 
   udisks_manager_complete_get_block_devices  (object,
                                               invocation,
@@ -1245,9 +1248,11 @@ handle_resolve_device (UDisksManager         *object,
     }
 
   ret_paths = g_new0 (const gchar *, num_found + 1);
-  for (i = 0,ret_p = ret; ret_p != NULL; ret_p = ret_p->next, i++)
+  for (i = 0,ret_p = ret; ret_p != NULL; ret_p = ret_p->next)
     {
-      ret_paths[i] = g_dbus_object_get_object_path (g_dbus_interface_get_object (G_DBUS_INTERFACE (ret_p->data)));
+      GDBusObject *block_object = g_dbus_interface_get_object (G_DBUS_INTERFACE (ret_p->data));
+      if (block_object)
+        ret_paths[i++] = g_dbus_object_get_object_path (block_object);
     }
 
   udisks_manager_complete_resolve_device (object,
-- 
2.33.0

