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From:   Sonny Sasaka <sonnysasaka@chromium.org>
To:     linux-bluetooth@vger.kernel.org
Cc:     Sonny Sasaka <sonnysasaka@chromium.org>
Subject: [PATCH BlueZ v2] input/hog: Fix crashes of UAF of hog->attr
Date:   Wed, 27 Jan 2021 22:39:01 -0800
Message-Id: <20210128063901.1362-1-sonnysasaka@chromium.org>
MIME-Version: 1.0
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hog->attr does not own pointer, so it may be invalid when hog object
gets re-attached at bt_hog_attach(). To solve this, this patch
intentionally clears hog->attr at bt_hog_detach() to mark it as invalid
so that it can be repopulated with the valid pointer at bt_hog_attach().
The same applies to all sub-instances.

Sample stack trace:
* thread #1, stop reason = signal SIGSEGV
  * frame #0: 0x05ad49f2 bluetoothd`<name omitted> at gatt-db.c:1428
    frame #1: 0x05a91922 bluetoothd`bt_hog_attach at hog-lib.c:1694
    frame #2: 0x05a9160e bluetoothd`hog_accept at hog.c:212
    frame #3: 0x05ab4784 bluetoothd`service_accept at service.c:203
    frame #4: 0x05aba1e6 bluetoothd`device_attach_att at device.c:4542
    frame #5: 0x05a9c4a2 bluetoothd`connect_cb at gatt-database.c:656
    frame #6: 0x05a98e8c bluetoothd`server_cb at btio.c:264
    frame #7: 0xec8e6a1a libglib-2.0.so.0`g_main_context_dispatch at gmain.c:3325
    frame #8: 0xec8e6c58 libglib-2.0.so.0`g_main_context_iterate at gmain.c:4119
    frame #9: 0xec8e6e52 libglib-2.0.so.0`g_main_loop_run at gmain.c:4317
    frame #10: 0x05ad582e bluetoothd`mainloop_run at mainloop-glib.c:79
    frame #11: 0x05ad5a64 bluetoothd`mainloop_run_with_signal at mainloop-notify.c:201
    frame #12: 0x05ac35ac bluetoothd`main at main.c:1103
    frame #13: 0xec6ed0a2 libc.so.6`__libc_start_main at libc-start.c:308

---
 profiles/input/hog-lib.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/profiles/input/hog-lib.c b/profiles/input/hog-lib.c
index 1f132aa4c..711bda73c 100644
--- a/profiles/input/hog-lib.c
+++ b/profiles/input/hog-lib.c
@@ -1651,12 +1651,19 @@ static void primary_cb(uint8_t status, GSList *services, void *user_data)
 bool bt_hog_attach(struct bt_hog *hog, void *gatt)
 {
 	GSList *l;
+	bt_uuid_t uuid;
 
 	if (hog->attrib)
 		return false;
 
 	hog->attrib = g_attrib_ref(gatt);
 
+	if (!hog->attr && hog->gatt_db) {
+		bt_uuid16_create(&uuid, HOG_UUID16);
+		gatt_db_foreach_service(hog->gatt_db, &uuid,
+					foreach_hog_service, hog);
+	}
+
 	if (!hog->attr && !hog->primary) {
 		discover_primary(hog, hog->attrib, NULL, primary_cb, hog);
 		return true;
@@ -1744,6 +1751,15 @@ void bt_hog_detach(struct bt_hog *hog)
 		bt_hog_detach(instance);
 	}
 
+	/* hog->attr doesn't own pointer, so it may be invalid when this hog
+	 * object gets re-attached with bt_hog_attach(). So intentionally mark
+	 * it as invalid and remove all instances so that the instances can be
+	 * re-attached at bt_hog_attach().
+	 */
+	hog->attr = NULL;
+	g_slist_free_full(hog->instances, hog_free);
+	hog->instances = NULL;
+
 	for (l = hog->reports; l; l = l->next) {
 		struct report *r = l->data;
 
-- 
2.29.2