Message-ID: <CABBYNZLFeeqMpWi4r5Dqh3UyG4r56VatcUMvZ4MRw=K0LOs8xw@mail.gmail.com>
Date: Mon, 15 Sep 2025 12:16:53 -0400
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Cen Zhang <zzzccc427@...il.com>
Cc: johan.hedberg@...il.com, marcel@...tmann.org, linux-kernel@...r.kernel.org, 
	baijiaju1990@...il.com, zhenghaoran154@...il.com, r33s3n6@...il.com, 
	linux-bluetooth@...r.kernel.org, "gality369@...il.com" <gality369@...il.com>
Subject: Re: [BUG]: slab-use-after-free Read in mgmt_set_powered_complete

Hi Cen,

On Mon, Sep 15, 2025 at 11:40 AM Cen Zhang <zzzccc427@...il.com> wrote:
>
> Hi Luiz,
>
> Thank you for the nice patch. I've been testing your patch for some
> time now, and it appears to have successfully resolved the original
> issue.
>
> However, during my extended testing, I discovered two similar bugs
> that might be worth fixing together. Here's the detailed report:
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in set_le_sync+0x86/0x810
> net/bluetooth/mgmt.c:2096
> Read of size 8 at addr ffff888147503220 by task kworker/u17:6/352
>
> CPU: 3 UID: 0 PID: 352 Comm: kworker/u17:6 Not tainted
> 6.17.0-rc5-ge5bbb70171d1-dirty #15 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
>  set_le_sync+0x86/0x810 net/bluetooth/mgmt.c:2096

Looks like we are still accessing things like cmd->param before
checking if that is still valid.

>  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
>  </TASK>
>
> Allocated by task 193:
>  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_le+0xd73/0x15f0 net/bluetooth/mgmt.c:2547
>  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 6434:
>  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_off+0x19e/0x3e0 net/bluetooth/mgmt.c:9479
>  hci_dev_close_sync+0x1064/0x2c10 net/bluetooth/hci_sync.c:5290
>  hci_dev_do_close net/bluetooth/hci_core.c:501 [inline]
>  hci_dev_close+0x232/0x460 net/bluetooth/hci_core.c:526
>  hci_sock_ioctl+0x785/0x1000 net/bluetooth/hci_sock.c:1135
>  sock_do_ioctl+0x7f/0x2e0 net/socket.c:1238
>  sock_ioctl+0x521/0x6a0 net/socket.c:1359
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:598 [inline]
>  __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
>  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
>
> The buggy address belongs to the object at ffff888147503200
>  which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 32 bytes inside of
>  freed 96-byte region [ffff888147503200, ffff888147503260)
> ==================================================================
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in set_name_complete+0x8e/0x790
> net/bluetooth/mgmt.c:3890
> Read of size 8 at addr ffff888145c595a0 by task kworker/u17:3/364
>
> CPU: 0 UID: 0 PID: 364 Comm: kworker/u17:3 Not tainted
> 6.17.0-rc5-ge5bbb70171d1-dirty #15 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
>  set_name_complete+0x8e/0x790 net/bluetooth/mgmt.c:3890
>  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 191:
>  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_local_name+0x390/0x910 net/bluetooth/mgmt.c:3975
>  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 23433:
>  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_off+0x19e/0x3e0 net/bluetooth/mgmt.c:9479
>  hci_dev_close_sync+0x1064/0x2c10 net/bluetooth/hci_sync.c:5290
>  hci_dev_do_close net/bluetooth/hci_core.c:501 [inline]
>  hci_dev_close+0x232/0x460 net/bluetooth/hci_core.c:526
>  hci_sock_ioctl+0x785/0x1000 net/bluetooth/hci_sock.c:1135
>  sock_do_ioctl+0x7f/0x2e0 net/socket.c:1238
>  sock_ioctl+0x521/0x6a0 net/socket.c:1359
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:598 [inline]
>  __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
>  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
>
> The buggy address belongs to the object at ffff888145c59580
>  which belongs to the cache kmalloc-96 of size 96
> The buggy address is located 32 bytes inside of
>  freed 96-byte region [ffff888145c59580, ffff888145c595e0)
>
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x145c59
> flags: 0x200000000000000(node=0|zone=2)
> page_type: f5(slab)
> raw: 0200000000000000 ffff888100042280 ffffea0004579a00 dead000000000002
> raw: 0000000000000000 0000000000200020 00000000f5000000 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff888145c59480: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>  ffff888145c59500: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> >ffff888145c59580: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>                                ^
>  ffff888145c59600: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>  ffff888145c59680: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ==================================================================
>
>
> Best regards,
> Cen Zhang
>
> Luiz Augusto von Dentz <luiz.dentz@...il.com> 于2025年9月15日周一 20:59写道：
> >
> > Hi Cen,
> >
> > On Fri, Sep 12, 2025 at 11:01 PM cen zhang <zzzccc427@...il.com> wrote:
> > >
> > > 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
> >
> > Looks like this is the result of trying to access the cmd->hdev, which
> > is definitely wrong since the whole point of the function is to try to
> > determine if cmd is still valid, so please try with the v5.
> >
> > >  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@...il.com> 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@mail.gmail.com/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@...il.com> 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@...il.com> 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.
> >
> >
> >
> > --
> > Luiz Augusto von Dentz



-- 
Luiz Augusto von Dentz

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