Hi Luiz,
I've just started testing the patch, and it seems to have introduced a
new issue. I've attached the detailed report below:
==================================================================
BUG: KASAN: slab-use-after-free in mgmt_pending_valid+0x8f/0x7e0
net/bluetooth/mgmt_util.c:330
Read of size 8 at addr ffff888140eae198 by task kworker/u17:2/82
CPU: 1 UID: 0 PID: 82 Comm: kworker/u17:2 Not tainted
6.17.0-rc5-ge5bbb70171d1-dirty #8 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0xca/0x130 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x171/0x7f0 mm/kasan/report.c:482
kasan_report+0x139/0x170 mm/kasan/report.c:595
mgmt_pending_valid+0x8f/0x7e0 net/bluetooth/mgmt_util.c:330
mgmt_set_powered_complete+0x81/0xf20 net/bluetooth/mgmt.c:1326
hci_cmd_sync_work+0x8df/0xaf0 net/bluetooth/hci_sync.c:334
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0x7a8/0x1030 kernel/workqueue.c:3319
worker_thread+0xb97/0x11d0 kernel/workqueue.c:3400
kthread+0x3d4/0x800 kernel/kthread.c:463
ret_from_fork+0x13b/0x1e0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Allocated by task 195:
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:388 [inline]
__kasan_kmalloc+0x72/0x90 mm/kasan/common.c:405
kmalloc_noprof include/linux/slab.h:905 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]
mgmt_pending_new+0xcd/0x580 net/bluetooth/mgmt_util.c:269
mgmt_pending_add+0x54/0x410 net/bluetooth/mgmt_util.c:296
set_powered+0x8c6/0xea0 net/bluetooth/mgmt.c:1406
hci_mgmt_cmd+0x1ee4/0x33f0 net/bluetooth/hci_sock.c:1719
hci_sock_sendmsg+0xcb0/0x2510 net/bluetooth/hci_sock.c:1839
sock_sendmsg_nosec net/socket.c:714 [inline]
__sock_sendmsg+0x21c/0x270 net/socket.c:729
sock_write_iter+0x1b7/0x250 net/socket.c:1179
do_iter_readv_writev+0x598/0x760
vfs_writev+0x3c8/0xd20 fs/read_write.c:1057
do_writev+0x105/0x270 fs/read_write.c:1103
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 82:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:243 [inline]
__kasan_slab_free+0x41/0x50 mm/kasan/common.c:275
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2428 [inline]
slab_free mm/slub.c:4701 [inline]
kfree+0x189/0x390 mm/slub.c:4900
mgmt_pending_free net/bluetooth/mgmt_util.c:311 [inline]
mgmt_pending_foreach+0x6c4/0x8a0 net/bluetooth/mgmt_util.c:257
mgmt_power_on+0x43d/0x5e0 net/bluetooth/mgmt.c:9448
hci_dev_open_sync+0x44fa/0x5060 net/bluetooth/hci_sync.c:5137
hci_power_on_sync net/bluetooth/hci_sync.c:5376 [inline]
hci_set_powered_sync+0x43e/0xfa0 net/bluetooth/hci_sync.c:5768
set_powered_sync+0x1e0/0x2c0 net/bluetooth/mgmt.c:1369
hci_cmd_sync_work+0x798/0xaf0 net/bluetooth/hci_sync.c:332
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0x7a8/0x1030 kernel/workqueue.c:3319
worker_thread+0xb97/0x11d0 kernel/workqueue.c:3400
kthread+0x3d4/0x800 kernel/kthread.c:463
ret_from_fork+0x13b/0x1e0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
The buggy address belongs to the object at ffff888140eae180
which belongs to the cache kmalloc-96 of size 96
The buggy address is located 24 bytes inside of
freed 96-byte region [ffff888140eae180, ffff888140eae1e0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000
index:0xffff888140eae200 pfn:0x140eae
flags: 0x200000000000200(workingset|node=0|zone=2)
page_type: f5(slab)
raw: 0200000000000200 ffff888100042280 ffffea0004763ad0 ffffea0004763a90
raw: ffff888140eae200 000000000020001f 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888140eae080: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff888140eae100: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff888140eae180: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
^
ffff888140eae200: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff888140eae280: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================
Best regards,
Cen Zhang
cen zhang <zzzccc427@xxxxxxxxx> 于2025年9月13日周六 10:16写道：
>
> Hi Luiz,
>
> Thanks for your patch! It not only addresses the TOCTOU issue we
> discussed but may also fix another bug I reported
> (https://lore.kernel.org/linux-bluetooth/CAFRLqsWWMnrZ6y8MUMUSK=tmAb3r8_jfSwqforOoR8_-=XgX7g@xxxxxxxxxxxxxx/T/#u).
>
> I will test it soon to confirm.
>
> Thanks again for the great work.
>
> Best regards,
>
> Cen Zhang
>
> Luiz Augusto von Dentz <luiz.dentz@xxxxxxxxx> 于2025年9月13日周六 02:29写道：
> >
> > Hi Cen,
> >
> > On Fri, Sep 12, 2025 at 11:59 AM cen zhang <zzzccc427@xxxxxxxxx> wrote:
> > >
> > > Hi Luiz,
> > >
> > > Thank you for your quick response and the important clarification
> > > about hci_cmd_sync_dequeue().
> > >
> > > You are absolutely correct - I was indeed referring to the TOCTOU
> > > problem in pending_find(), not the -ECANCELED check. The
> > > hci_cmd_sync_dequeue() call in cmd_complete_rsp() is a crucial detail
> > > that I initially overlooked in my analysis.
> > >
> > > After examining the code more carefully, I can see that while
> > > hci_cmd_sync_dequeue() does attempt to remove pending sync commands
> > > from the queue, but it cannot prevent the race condition we're seeing.
> > > The fundamental issue is that hci_cmd_sync_dequeue() can only remove
> > > work items that are still queued, but cannot stop work items that are
> > > already executing or about to execute their completion callbacks.
> > >
> > > The race window occurs when:
> > > 1. mgmt_set_powered_complete() is about to execute (work item has been dequeued)
> > > 2. mgmt_index_removed() -> mgmt_pending_foreach() -> cmd_complete_rsp() executes
> > > 3. hci_cmd_sync_dequeue() removes queued items but cannot affect the
> > > already-running callback
> > > 4. mgmt_pending_free() frees the cmd object
> > > 5. mgmt_set_powered_complete() still executes and accesses freed cmd->param
> > >
> > > I am sorry that I haven't get a reliable reproducer from syzkaller for
> > > this bug may be due to it is timing-sensitive.
> >
> > Let's try to fix all instances then, since apparently there is more
> > than one cmd with this pattern, please test with the attached patch.
