Re: [PATCH v2 1/3] Bluetooth: MGMT: Fix possible UAF on mgmt_add_adv_patterns_monitor_sync

Paul Menzel <pmenzel@xxxxxxxxxxxxx> · Wed, 10 Sep 2025 00:04:25 +0200

Dear Luiz,


Thank you for the patch.

Am 09.09.25 um 23:58 schrieb Luiz Augusto von Dentz:
From: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>

I’d love to see a paragraph in the commit message explaining the problem 
next to the trace below.

BUG: KASAN: slab-use-after-free in mgmt_add_adv_patterns_monitor_sync+0x35/0x50 net/bluetooth/mgmt.c:5223
Read of size 8 at addr ffff8880709d4dc0 by task kworker/u11:0/55

CPU: 0 UID: 0 PID: 55 Comm: kworker/u11:0 Not tainted 6.16.4 #2 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
  <TASK>
  dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
  print_address_description mm/kasan/report.c:378 [inline]
  print_report+0xca/0x240 mm/kasan/report.c:482
  kasan_report+0x118/0x150 mm/kasan/report.c:595
  mgmt_add_adv_patterns_monitor_sync+0x35/0x50 net/bluetooth/mgmt.c:5223
  hci_cmd_sync_work+0x210/0x3a0 net/bluetooth/hci_sync.c:332
  process_one_work kernel/workqueue.c:3238 [inline]
  process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3321
  worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
  kthread+0x711/0x8a0 kernel/kthread.c:464
  ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
  ret_from_fork_asm+0x1a/0x30 home/kwqcheii/source/fuzzing/kernel/kasan/linux-6.16.4/arch/x86/entry/entry_64.S:245
  </TASK>

Allocated by task 12210:
  kasan_save_stack mm/kasan/common.c:47 [inline]
  kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
  poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
  __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
  kasan_kmalloc include/linux/kasan.h:260 [inline]
  __kmalloc_cache_noprof+0x230/0x3d0 mm/slub.c:4364
  kmalloc_noprof include/linux/slab.h:905 [inline]
  kzalloc_noprof include/linux/slab.h:1039 [inline]
  mgmt_pending_new+0x65/0x1e0 net/bluetooth/mgmt_util.c:269
  mgmt_pending_add+0x35/0x140 net/bluetooth/mgmt_util.c:296
  __add_adv_patterns_monitor+0x130/0x200 net/bluetooth/mgmt.c:5247
  add_adv_patterns_monitor+0x214/0x360 net/bluetooth/mgmt.c:5364
  hci_mgmt_cmd+0x9c9/0xef0 net/bluetooth/hci_sock.c:1719
  hci_sock_sendmsg+0x6ca/0xef0 net/bluetooth/hci_sock.c:1839
  sock_sendmsg_nosec net/socket.c:714 [inline]
  __sock_sendmsg+0x219/0x270 net/socket.c:729
  sock_write_iter+0x258/0x330 net/socket.c:1133
  new_sync_write fs/read_write.c:593 [inline]
  vfs_write+0x5c9/0xb30 fs/read_write.c:686
  ksys_write+0x145/0x250 fs/read_write.c:738
  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
  do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 12221:
  kasan_save_stack mm/kasan/common.c:47 [inline]
  kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
  kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
  poison_slab_object mm/kasan/common.c:247 [inline]
  __kasan_slab_free+0x62/0x70 mm/kasan/common.c:264
  kasan_slab_free include/linux/kasan.h:233 [inline]
  slab_free_hook mm/slub.c:2381 [inline]
  slab_free mm/slub.c:4648 [inline]
  kfree+0x18e/0x440 mm/slub.c:4847
  mgmt_pending_free net/bluetooth/mgmt_util.c:311 [inline]
  mgmt_pending_foreach+0x30d/0x380 net/bluetooth/mgmt_util.c:257
  __mgmt_power_off+0x169/0x350 net/bluetooth/mgmt.c:9444
  hci_dev_close_sync+0x754/0x1330 net/bluetooth/hci_sync.c:5290
  hci_dev_do_close net/bluetooth/hci_core.c:501 [inline]
  hci_dev_close+0x108/0x200 net/bluetooth/hci_core.c:526
  sock_do_ioctl+0xd9/0x300 net/socket.c:1192
  sock_ioctl+0x576/0x790 net/socket.c:1313
  vfs_ioctl fs/ioctl.c:51 [inline]
  __do_sys_ioctl fs/ioctl.c:907 [inline]
  __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893
  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
  do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fixes: b747a83690c8 ("Bluetooth: hci_sync: Refactor add Adv Monitor")
Closes: https://syzkaller.appspot.com/bug?extid=e8651419c44dbc2b8768
Reported-by: syzbot+e8651419c44dbc2b8768@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx>
---
  net/bluetooth/mgmt.c | 12 ++++++++++++
  1 file changed, 12 insertions(+)

diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
index 989321b1ea27..165e8d8cff96 100644
--- a/net/bluetooth/mgmt.c
+++ b/net/bluetooth/mgmt.c
@@ -5189,6 +5189,14 @@ static void mgmt_add_adv_patterns_monitor_complete(struct hci_dev *hdev,
  	struct mgmt_pending_cmd *cmd = data;
  	struct adv_monitor *monitor = cmd->user_data;
  
+	/* This is likely the result of hdev being closed and mgmt_index_removed

I’d write what *This* means. Maybe: Status of ECANCELED is …

+	 * is attempting to clean up any pending command so
+	 * hci_adv_monitors_clear is about to be called which will take care of
+	 * freeing the adv_monitor instances.
+	 */
+	if (status == -ECANCELED)
+		return;
+
  	hci_dev_lock(hdev);
  
  	rp.monitor_handle = cpu_to_le16(monitor->handle);
@@ -5215,6 +5223,10 @@ static int mgmt_add_adv_patterns_monitor_sync(struct hci_dev *hdev, void *data)
  	struct mgmt_pending_cmd *cmd = data;
  	struct adv_monitor *monitor = cmd->user_data;
  
+	if (cmd != pending_find(MGMT_OP_ADD_ADV_PATTERNS_MONITOR, hdev) &&
+	    cmd != pending_find(MGMT_OP_ADD_ADV_PATTERNS_MONITOR_RSSI, hdev))
+		return -ECANCELED;
+
  	return hci_add_adv_monitor(hdev, monitor);
  }
  


Kind regards,

Paul







