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From:   Pauli Virtanen <pav@iki.fi>
To:     linux-bluetooth@vger.kernel.org
Cc:     Pauli Virtanen <pav@iki.fi>
Subject: [PATCH v2 2/4] Bluetooth: hci_sync: fix use-after-free in hci_disconnect_all_sync
Date:   Sun,  6 Aug 2023 23:18:38 +0300
Message-ID: <7b81cf669e2172b2e69d3b4fe6c9c256f5249c69.1691352503.git.pav@iki.fi>
In-Reply-To: <b2ed850478c905299c40154c1d6dfc304a93d77a.1691352503.git.pav@iki.fi>
References: <b2ed850478c905299c40154c1d6dfc304a93d77a.1691352503.git.pav@iki.fi>
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Use-after-free occurs in hci_disconnect_all_sync if a connection is
deleted by concurrent processing of a controller event.  This can occur
while waiting for controller events (big time window) or at other times
(less likely).

Fix the iteration in hci_disconnect_all_sync to allow hci_conn to be
deleted at any time.

UAF crash log:
==================================================================
BUG: KASAN: slab-use-after-free in hci_set_powered_sync (net/bluetooth/hci_sync.c:5424) [bluetooth]
Read of size 8 at addr ffff888009d9c000 by task kworker/u9:0/124

CPU: 0 PID: 124 Comm: kworker/u9:0 Tainted: G        W          6.5.0-rc1+ #10
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014
Workqueue: hci0 hci_cmd_sync_work [bluetooth]
Call Trace:
 <TASK>
 dump_stack_lvl+0x5b/0x90
 print_report+0xcf/0x670
 ? __virt_addr_valid+0xdd/0x160
 ? hci_set_powered_sync+0x2c9/0x4a0 [bluetooth]
 kasan_report+0xa6/0xe0
 ? hci_set_powered_sync+0x2c9/0x4a0 [bluetooth]
 ? __pfx_set_powered_sync+0x10/0x10 [bluetooth]
 hci_set_powered_sync+0x2c9/0x4a0 [bluetooth]
 ? __pfx_hci_set_powered_sync+0x10/0x10 [bluetooth]
 ? __pfx_lock_release+0x10/0x10
 ? __pfx_set_powered_sync+0x10/0x10 [bluetooth]
 hci_cmd_sync_work+0x137/0x220 [bluetooth]
 process_one_work+0x526/0x9d0
 ? __pfx_process_one_work+0x10/0x10
 ? __pfx_do_raw_spin_lock+0x10/0x10
 ? mark_held_locks+0x1a/0x90
 worker_thread+0x92/0x630
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x196/0x1e0
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x2c/0x50
 </TASK>

Allocated by task 1782:
 kasan_save_stack+0x33/0x60
 kasan_set_track+0x25/0x30
 __kasan_kmalloc+0x8f/0xa0
 hci_conn_add+0xa5/0xa80 [bluetooth]
 hci_bind_cis+0x881/0x9b0 [bluetooth]
 iso_connect_cis+0x121/0x520 [bluetooth]
 iso_sock_connect+0x3f6/0x790 [bluetooth]
 __sys_connect+0x109/0x130
 __x64_sys_connect+0x40/0x50
 do_syscall_64+0x60/0x90
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Freed by task 695:
 kasan_save_stack+0x33/0x60
 kasan_set_track+0x25/0x30
 kasan_save_free_info+0x2b/0x50
 __kasan_slab_free+0x10a/0x180
 __kmem_cache_free+0x14d/0x2e0
 device_release+0x5d/0xf0
 kobject_put+0xdf/0x270
 hci_disconn_complete_evt+0x274/0x3a0 [bluetooth]
 hci_event_packet+0x579/0x7e0 [bluetooth]
 hci_rx_work+0x287/0xaa0 [bluetooth]
 process_one_work+0x526/0x9d0
 worker_thread+0x92/0x630
 kthread+0x196/0x1e0
 ret_from_fork+0x2c/0x50
==================================================================

Fixes: 182ee45da083 ("Bluetooth: hci_sync: Rework hci_suspend_notifier")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
---

Notes:
    v2: use only valid values for abort_reason, in case we fail before
        handling all conns
    
    This is still a bit clumsy, a separate flag indicating if connection was
    aborted yet could be better.

 net/bluetooth/hci_sync.c | 47 ++++++++++++++++++++++++++++++++++------
 1 file changed, 40 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 51ff682f66e0..228259f44815 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -5415,16 +5415,49 @@ int hci_abort_conn_sync(struct hci_dev *hdev, struct hci_conn *conn, u8 reason)
 
 static int hci_disconnect_all_sync(struct hci_dev *hdev, u8 reason)
 {
-	struct hci_conn *conn, *tmp;
-	int err;
+	struct hci_conn *c, *conn;
+	int err = 0;
 
-	list_for_each_entry_safe(conn, tmp, &hdev->conn_hash.list, list) {
-		err = hci_abort_conn_sync(hdev, conn, reason);
-		if (err)
-			return err;
+	rcu_read_lock();
+
+	/* Any conn may be gone while waiting for events, iterate safely.
+	 * If conn is in conn_hash and we didn't abort it, it probably
+	 * has not yet been aborted.
+	 */
+	list_for_each_entry_rcu(c, &hdev->conn_hash.list, list) {
+		if (c->abort_reason != reason)
+			continue;
+
+		c->abort_reason = (reason != HCI_ERROR_REMOTE_USER_TERM) ?
+			HCI_ERROR_REMOTE_USER_TERM : HCI_ERROR_UNSPECIFIED;
 	}
 
-	return 0;
+	do {
+		conn = NULL;
+		list_for_each_entry_rcu(c, &hdev->conn_hash.list, list) {
+			if (c->abort_reason == reason)
+				continue;
+
+			conn = c;
+			break;
+		}
+		if (!conn)
+			break;
+
+		conn->abort_reason = reason;
+		hci_conn_get(conn);
+
+		rcu_read_unlock();
+
+		err = hci_abort_conn_sync(hdev, conn, reason);
+		hci_conn_put(conn);
+
+		rcu_read_lock();
+	} while (!err);
+
+	rcu_read_unlock();
+
+	return err;
 }
 
 /* This function perform power off HCI command sequence as follows:
-- 
2.41.0