bluetooth: use-after-free in vhci_send_frame

[Dmitry Vyukov]

Hello,

I've got the following use-after-free reports while running syzkaller
fuzzer. Unfortunately no reproducer. But this happened when system was
busy reacting on sysrq t, so probably some unexpected delay happended.

On commit 92e963f50fc74041b5e9e744c330dca48e04f08d.

==================================================================
BUG: KASAN: use-after-free in do_raw_spin_unlock+0x228/0x240 at addr
ffff88003a8a9ed8
Write of size 8 by task kworker/u12:2/10322
=============================================================================
BUG kmalloc-512 (Tainted: G B ): kasan: bad access detected
-----------------------------------------------------------------------------

INFO: Allocated in vhci_open+0x50/0x350 age=6743 cpu=0 pid=10397
[< none >] ___slab_alloc+0x564/0x5b0 mm/slub.c:2470
[< none >] __slab_alloc+0x66/0xc0 mm/slub.c:2499
[< inline >] slab_alloc_node mm/slub.c:2562
[< inline >] slab_alloc mm/slub.c:2604
[< none >] kmem_cache_alloc_trace+0x25c/0x300 mm/slub.c:2621
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] kzalloc include/linux/slab.h:607
[< none >] vhci_open+0x50/0x350 drivers/bluetooth/hci_vhci.c:316
[< none >] misc_open+0x388/0x520 drivers/char/misc.c:153
[< none >] chrdev_open+0x22a/0x4c0 fs/char_dev.c:388
[< none >] do_dentry_open+0x6a2/0xcb0 fs/open.c:736
[< none >] vfs_open+0x17b/0x1f0 fs/open.c:853
[< inline >] do_last fs/namei.c:3254
[< none >] path_openat+0xde9/0x5e30 fs/namei.c:3386
[< none >] do_filp_open+0x18e/0x250 fs/namei.c:3421
[< none >] do_sys_open+0x1fc/0x420 fs/open.c:1022
[< inline >] SYSC_open fs/open.c:1040
[< none >] SyS_open+0x2d/0x40 fs/open.c:1035
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Freed in vhci_release+0xae/0xe0 age=2072 cpu=2 pid=10397
[< none >] __slab_free+0x1fc/0x320 mm/slub.c:2680
[< inline >] slab_free mm/slub.c:2835
[< none >] kfree+0x2ac/0x2c0 mm/slub.c:3664
[< none >] vhci_release+0xae/0xe0 drivers/bluetooth/hci_vhci.c:346
[< none >] __fput+0x236/0x780 fs/file_table.c:208
[< none >] ____fput+0x15/0x20 fs/file_table.c:244
[< none >] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[< none >] do_exit+0x8b5/0x2cb0 kernel/exit.c:748
[< none >] do_group_exit+0x108/0x330 kernel/exit.c:878
[< none >] get_signal+0x5e4/0x14f0 kernel/signal.c:2307
[< none >] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
[< none >] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[< none >] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
[< none >] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281

INFO: Slab 0xffffea0000ea2a00 objects=16 used=14 fp=0xffff88003a8a9ec0
flags=0x1fffc0000004080
INFO: Object 0xffff88003a8a9ec0 @offset=7872 fp=0xffff88003a8a9ae8
CPU: 1 PID: 10322 Comm: kworker/u12:2 Tainted: G B 4.5.0-rc1+ #300
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: hci0 hci_cmd_work
00000000ffffffff ffff88003634f9f8 ffffffff82be118d ffff88003e804f00
ffff88003a8a9ec0 ffff88003a8a8000 ffff88003634fa28 ffffffff8175b434
ffff88003e804f00 ffffea0000ea2a00 ffff88003a8a9ec0 0000000000000001

Call Trace:
[< inline >] kasan_report mm/kasan/report.c:274
[<ffffffff81764f9e>] __asan_report_store8_noabort+0x3e/0x40
mm/kasan/report.c:300
[< inline >] debug_spin_unlock kernel/locking/spinlock_debug.c:102
[<ffffffff81466608>] do_raw_spin_unlock+0x228/0x240
kernel/locking/spinlock_debug.c:158
[< inline >] __raw_spin_unlock_irqrestore
include/linux/spinlock_api_smp.h:161
[<ffffffff86652cf7>] _raw_spin_unlock_irqrestore+0x27/0xc0
kernel/locking/spinlock.c:191
[< inline >] spin_unlock_irqrestore include/linux/spinlock.h:362
[<ffffffff8143975f>] __wake_up+0x3f/0x50 kernel/sched/wait.c:96
[<ffffffff8484b983>] vhci_send_frame+0xc3/0x100 drivers/bluetooth/hci_vhci.c:86
[<ffffffff85d38315>] hci_send_frame+0x1f5/0x310 net/bluetooth/hci_core.c:3316
[<ffffffff85d385bf>] hci_cmd_work+0x18f/0x2e0 net/bluetooth/hci_core.c:4196
[<ffffffff813a2386>] process_one_work+0x796/0x1440 kernel/workqueue.c:2037
[<ffffffff813a310b>] worker_thread+0xdb/0xfc0 kernel/workqueue.c:2171
[<ffffffff813b637f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
[<ffffffff866535ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
==================================================================

==================================================================
BUG: KASAN: use-after-free in do_raw_spin_lock+0x281/0x2b0 at addr
ffff88003a8a9f2c
Read of size 4 by task kworker/u12:0/3554
=============================================================================
BUG kmalloc-512 (Tainted: G B ): kasan: bad access detected
-----------------------------------------------------------------------------

INFO: Allocated in vhci_open+0x50/0x350 age=16305 cpu=0 pid=10397
[< none >] ___slab_alloc+0x564/0x5b0 mm/slub.c:2470
[< none >] __slab_alloc+0x66/0xc0 mm/slub.c:2499
[< inline >] slab_alloc_node mm/slub.c:2562
[< inline >] slab_alloc mm/slub.c:2604
[< none >] kmem_cache_alloc_trace+0x25c/0x300 mm/slub.c:2621
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] kzalloc include/linux/slab.h:607
[< none >] vhci_open+0x50/0x350 drivers/bluetooth/hci_vhci.c:316
[< none >] misc_open+0x388/0x520 drivers/char/misc.c:153
[< none >] chrdev_open+0x22a/0x4c0 fs/char_dev.c:388
[< none >] do_dentry_open+0x6a2/0xcb0 fs/open.c:736
[< none >] vfs_open+0x17b/0x1f0 fs/open.c:853
[< inline >] do_last fs/namei.c:3254
[< none >] path_openat+0xde9/0x5e30 fs/namei.c:3386
[< none >] do_filp_open+0x18e/0x250 fs/namei.c:3421
[< none >] do_sys_open+0x1fc/0x420 fs/open.c:1022
[< inline >] SYSC_open fs/open.c:1040
[< none >] SyS_open+0x2d/0x40 fs/open.c:1035
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Freed in vhci_release+0xae/0xe0 age=11634 cpu=2 pid=10397
[< none >] __slab_free+0x1fc/0x320 mm/slub.c:2680
[< inline >] slab_free mm/slub.c:2835
[< none >] kfree+0x2ac/0x2c0 mm/slub.c:3664
[< none >] vhci_release+0xae/0xe0 drivers/bluetooth/hci_vhci.c:346
[< none >] __fput+0x236/0x780 fs/file_table.c:208
[< none >] ____fput+0x15/0x20 fs/file_table.c:244
[< none >] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[< none >] do_exit+0x8b5/0x2cb0 kernel/exit.c:748
[< none >] do_group_exit+0x108/0x330 kernel/exit.c:878
[< none >] get_signal+0x5e4/0x14f0 kernel/signal.c:2307
[< none >] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
[< none >] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[< none >] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
[< none >] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281

INFO: Slab 0xffffea0000ea2a00 objects=16 used=12 fp=0xffff88003a8aaa48
flags=0x1fffc0000004080
INFO: Object 0xffff88003a8a9ec0 @offset=7872 fp=0xffff88003a8a9338
CPU: 0 PID: 3554 Comm: kworker/u12:0 Tainted: G B 4.5.0-rc1+ #300
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: hci0 hci_power_on
00000000ffffffff ffff880036abf838 ffffffff82be118d ffff88003e804f00
ffff88003a8a9ec0 ffff88003a8a8000 ffff880036abf868 ffffffff8175b434
ffff88003e804f00 ffffea0000ea2a00 ffff88003a8a9ec0 ffff880036abfb30

Call Trace:
[< inline >] kasan_report mm/kasan/report.c:274
[<ffffffff81764e1e>] __asan_report_load4_noabort+0x3e/0x40
mm/kasan/report.c:294
[< inline >] debug_spin_lock_before kernel/locking/spinlock_debug.c:83
[<ffffffff814662e1>] do_raw_spin_lock+0x281/0x2b0
kernel/locking/spinlock_debug.c:135
[< inline >] __raw_spin_lock_irqsave
include/linux/spinlock_api_smp.h:119
[<ffffffff86652bd7>] _raw_spin_lock_irqsave+0xa7/0xd0
kernel/locking/spinlock.c:159
[<ffffffff854da1b2>] skb_dequeue+0x22/0x180 net/core/skbuff.c:2333
[<ffffffff854de656>] skb_queue_purge+0x26/0x40 net/core/skbuff.c:2371
[<ffffffff8484b9fb>] vhci_flush+0x3b/0x50 drivers/bluetooth/hci_vhci.c:74
[<ffffffff85d3a02f>] hci_dev_do_open+0x62f/0xf60 net/bluetooth/hci_core.c:1417
[<ffffffff85d42b98>] hci_power_on+0x108/0x4b0 net/bluetooth/hci_core.c:2027
[<ffffffff813a2386>] process_one_work+0x796/0x1440 kernel/workqueue.c:2037
[<ffffffff813a310b>] worker_thread+0xdb/0xfc0 kernel/workqueue.c:2171
[<ffffffff813b637f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
[<ffffffff866535ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
==================================================================
==================================================================
BUG: KASAN: use-after-free in skb_dequeue+0x153/0x180 at addr ffff88003a8a9f10
Read of size 8 by task kworker/u12:0/3554
=============================================================================
BUG kmalloc-512 (Tainted: G B ): kasan: bad access detected
-----------------------------------------------------------------------------

INFO: Allocated in vhci_open+0x50/0x350 age=16913 cpu=0 pid=10397
[< inline >] slab_alloc_node mm/slub.c:2562
[< inline >] slab_alloc mm/slub.c:2604
[< none >] kmem_cache_alloc_trace+0x25c/0x300 mm/slub.c:2621
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] kzalloc include/linux/slab.h:607
[< none >] vhci_open+0x50/0x350 drivers/bluetooth/hci_vhci.c:316
[< none >] misc_open+0x388/0x520 drivers/char/misc.c:153
[< none >] chrdev_open+0x22a/0x4c0 fs/char_dev.c:388
[< none >] do_dentry_open+0x6a2/0xcb0 fs/open.c:736
[< none >] vfs_open+0x17b/0x1f0 fs/open.c:853
[< inline >] do_last fs/namei.c:3254
[< none >] path_openat+0xde9/0x5e30 fs/namei.c:3386
[< none >] do_filp_open+0x18e/0x250 fs/namei.c:3421
[< none >] do_sys_open+0x1fc/0x420 fs/open.c:1022
[< inline >] SYSC_open fs/open.c:1040
[< none >] SyS_open+0x2d/0x40 fs/open.c:1035
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Freed in vhci_release+0xae/0xe0 age=12241 cpu=2 pid=10397
[< inline >] slab_free mm/slub.c:2835
[< none >] kfree+0x2ac/0x2c0 mm/slub.c:3664
[< none >] vhci_release+0xae/0xe0 drivers/bluetooth/hci_vhci.c:346
[< none >] __fput+0x236/0x780 fs/file_table.c:208
[< none >] ____fput+0x15/0x20 fs/file_table.c:244
[< none >] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[< none >] do_exit+0x8b5/0x2cb0 kernel/exit.c:748
[< none >] do_group_exit+0x108/0x330 kernel/exit.c:878
[< none >] get_signal+0x5e4/0x14f0 kernel/signal.c:2307
[< none >] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
[< none >] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[< none >] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
[< none >] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281

INFO: Slab 0xffffea0000ea2a00 objects=16 used=12 fp=0xffff88003a8aaa48
flags=0x1fffc0000004080
INFO: Object 0xffff88003a8a9ec0 @offset=7872 fp=0xffff88003a8a9338
CPU: 0 PID: 3554 Comm: kworker/u12:0 Tainted: G B 4.5.0-rc1+ #300
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: hci0 hci_power_on
00000000ffffffff ffff880036abf898 ffffffff82be118d ffff88003e804f00
ffff88003a8a9ec0 ffff88003a8a8000 ffff880036abf8c8 ffffffff8175b434
ffff88003e804f00 ffffea0000ea2a00 ffff88003a8a9ec0 0000000000000282

Call Trace:
[< inline >] kasan_report mm/kasan/report.c:274
[<ffffffff81764e5e>] __asan_report_load8_noabort+0x3e/0x40
mm/kasan/report.c:295
[< inline >] skb_peek include/linux/skbuff.h:1453
[< inline >] __skb_dequeue include/linux/skbuff.h:1735
[<ffffffff854da2e3>] skb_dequeue+0x153/0x180 net/core/skbuff.c:2334
[<ffffffff854de656>] skb_queue_purge+0x26/0x40 net/core/skbuff.c:2371
[<ffffffff8484b9fb>] vhci_flush+0x3b/0x50 drivers/bluetooth/hci_vhci.c:74
[<ffffffff85d3a02f>] hci_dev_do_open+0x62f/0xf60 net/bluetooth/hci_core.c:1417
[<ffffffff85d42b98>] hci_power_on+0x108/0x4b0 net/bluetooth/hci_core.c:2027
[<ffffffff813a2386>] process_one_work+0x796/0x1440 kernel/workqueue.c:2037
[<ffffffff813a310b>] worker_thread+0xdb/0xfc0 kernel/workqueue.c:2171
[<ffffffff813b637f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
[<ffffffff866535ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
==================================================================

[Dmitry Vyukov]

Ping.
Just got another one on 4.5-rc6

==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x4864/0x49c0 at addr
ffff8800353b8c08
Read of size 8 by task kworker/u12:2/1443
=============================================================================
BUG kmalloc-512 (Not tainted): kasan: bad access detected
-----------------------------------------------------------------------------

INFO: Allocated in vhci_open+0x50/0x350 age=1048 cpu=0 pid=1394
[< none >] ___slab_alloc+0x574/0x5c0 mm/slub.c:2464
[< none >] __slab_alloc+0x66/0xc0 mm/slub.c:2493
[< inline >] slab_alloc_node mm/slub.c:2556
[< inline >] slab_alloc mm/slub.c:2598
[< none >] kmem_cache_alloc_trace+0x27c/0x350 mm/slub.c:2615

[< inline >] kmalloc include/linux/slab.h:463
[< inline >] kzalloc include/linux/slab.h:607
[< none >] vhci_open+0x50/0x350 drivers/bluetooth/hci_vhci.c:316
[< none >] misc_open+0x388/0x520 drivers/char/misc.c:153
[< none >] chrdev_open+0x22a/0x4c0 fs/char_dev.c:388
[< none >] do_dentry_open+0x6a2/0xcb0 fs/open.c:736
[< none >] vfs_open+0x17b/0x1f0 fs/open.c:853

[< inline >] do_last fs/namei.c:3258
[< none >] path_openat+0x4849/0x5840 fs/namei.c:3394
[< none >] do_filp_open+0x18e/0x250 fs/namei.c:3429

[< none >] do_sys_open+0x1fc/0x420 fs/open.c:1022
[< inline >] SYSC_open fs/open.c:1040
[< none >] SyS_open+0x2d/0x40 fs/open.c:1035
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a
arch/x86/entry/entry_64.S:185

INFO: Freed in vhci_release+0xae/0xe0 age=23 cpu=2 pid=1394
[< none >] __slab_free+0x1fc/0x320 mm/slub.c:2674
[< inline >] slab_free mm/slub.c:2829
[< none >] kfree+0x303/0x320 mm/slub.c:3660

[< none >] vhci_release+0xae/0xe0 drivers/bluetooth/hci_vhci.c:346
[< none >] __fput+0x236/0x780 fs/file_table.c:208
[< none >] ____fput+0x15/0x20 fs/file_table.c:244
[< none >] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21

[< none >] do_exit+0xaf0/0x2d20 kernel/exit.c:748
[< none >] do_group_exit+0x108/0x330 kernel/exit.c:878
[< none >] get_signal+0x628/0x1560 kernel/signal.c:2307

[< none >] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
[< none >] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[< none >] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
[< none >] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281

INFO: Slab 0xffffea0000d4ee00 objects=16 used=15 fp=0xffff8800353b8b88
flags=0x1fffc0000004080
INFO: Object 0xffff8800353b8b88 @offset=2952 fp=0x (null)
CPU: 0 PID: 1443 Comm: kworker/u12:2 Tainted: G B 4.5.0-rc6+ #335

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: hci0 hci_cmd_work

ffffffff87b4d480 ffff880031427800 ffffffff82c0664f ffffffff00d4ee00
fffffbfff0f69a90 ffff88003e804f00 ffff8800353b8b88 ffff8800353b8000
ffffea0000d4ee00 0000000000000000 ffff880031427830 ffffffff81767194

Call Trace:
[< inline >] __dump_stack lib/dump_stack.c:15
[<ffffffff82c0664f>] dump_stack+0x12e/0x18f lib/dump_stack.c:51
[<ffffffff81767194>] print_trailer+0xf4/0x150 mm/slub.c:661
[<ffffffff8176e46f>] object_err+0x2f/0x40 mm/slub.c:691
[< inline >] print_address_description mm/kasan/report.c:138
[<ffffffff81770d96>] kasan_report_error+0x256/0x550 mm/kasan/report.c:251
[< inline >] kasan_report mm/kasan/report.c:274
[<ffffffff8177118e>] __asan_report_load8_noabort+0x3e/0x40
mm/kasan/report.c:295
[<ffffffff81460c04>] __lock_acquire+0x4864/0x49c0 kernel/locking/lockdep.c:3096
[<ffffffff81463269>] lock_acquire+0x1f9/0x460 kernel/locking/lockdep.c:3589
[< inline >] __raw_spin_lock_irqsave
include/linux/spinlock_api_smp.h:112
[<ffffffff866a1eaf>] _raw_spin_lock_irqsave+0x9f/0xd0
kernel/locking/spinlock.c:159
[<ffffffff85516c76>] skb_queue_tail+0x26/0x150 net/core/skbuff.c:2414
[<ffffffff84881fee>] vhci_send_frame+0xae/0x100 drivers/bluetooth/hci_vhci.c:84
[<ffffffff85d769b5>] hci_send_frame+0x1f5/0x310 net/bluetooth/hci_core.c:3316
[<ffffffff85d76c5f>] hci_cmd_work+0x18f/0x2e0 net/bluetooth/hci_core.c:4198
[<ffffffff813abf3b>] process_one_work+0x79b/0x1510 kernel/workqueue.c:2096
[<ffffffff813acd8b>] worker_thread+0xdb/0xfc0 kernel/workqueue.c:2230
[<ffffffff813bdd3f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
[<ffffffff866a28af>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
==================================================================

[Jiri Slaby]

FWIW I've just hit that too right now.

But I haven't hit it with 4.4 which I am fuzzing by the orders of
magnitude longer. But take it with grain of salt -- it could be a
coincidence, of course.

thanks,
--
js
suse labs

[Marcel Holtmann]

Hi Jiri,

do you know what the fuzzer was doing at this point. Is the fuzzer opening /dev/vhci device node? Since that would be the only way to actually get into that driver.

Regards

Marcel

[Dmitry Vyukov]

Check out the KASAN reports. They should answer your question.

[Marcel Holtmann]

Hi Dmitry,

that means very little to me actually. So is the real issue caused by opening /dev/vhci or is that theoretical one via some internal kernel compile time feature.

Regards

Marcel

[Dmitry Vyukov]

This is a real use-after-free bug that actually happened on my machine.

The memory was allocated inside of SyS_open syscall which called
vhci_open. So, yes, actual opening of /dev/vhci was definitely
involved:

INFO: Allocated in vhci_open+0x50/0x350 age=6743 cpu=0 pid=10397
[< none >] ___slab_alloc+0x564/0x5b0 mm/slub.c:2470
[< none >] __slab_alloc+0x66/0xc0 mm/slub.c:2499
[< inline >] slab_alloc_node mm/slub.c:2562
[< inline >] slab_alloc mm/slub.c:2604
[< none >] kmem_cache_alloc_trace+0x25c/0x300 mm/slub.c:2621
[< inline >] kmalloc include/linux/slab.h:463
[< inline >] kzalloc include/linux/slab.h:607
[< none >] vhci_open+0x50/0x350 drivers/bluetooth/hci_vhci.c:316
[< none >] misc_open+0x388/0x520 drivers/char/misc.c:153
[< none >] chrdev_open+0x22a/0x4c0 fs/char_dev.c:388
[< none >] do_dentry_open+0x6a2/0xcb0 fs/open.c:736
[< none >] vfs_open+0x17b/0x1f0 fs/open.c:853
[< inline >] do_last fs/namei.c:3254
[< none >] path_openat+0xde9/0x5e30 fs/namei.c:3386
[< none >] do_filp_open+0x18e/0x250 fs/namei.c:3421
[< none >] do_sys_open+0x1fc/0x420 fs/open.c:1022
[< inline >] SYSC_open fs/open.c:1040
[< none >] SyS_open+0x2d/0x40 fs/open.c:1035
[< none >] entry_SYSCALL_64_fastpath+0x16/0x7a

Then memory was freed here (by the same task):

INFO: Freed in vhci_release+0xae/0xe0 age=11634 cpu=2 pid=10397
[< none >] __slab_free+0x1fc/0x320 mm/slub.c:2680
[< inline >] slab_free mm/slub.c:2835
[< none >] kfree+0x2ac/0x2c0 mm/slub.c:3664
[< none >] vhci_release+0xae/0xe0 drivers/bluetooth/hci_vhci.c:346
[< none >] __fput+0x236/0x780 fs/file_table.c:208
[< none >] ____fput+0x15/0x20 fs/file_table.c:244
[< none >] task_work_run+0x170/0x210 kernel/task_work.c:115
[< inline >] exit_task_work include/linux/task_work.h:21
[< none >] do_exit+0x8b5/0x2cb0 kernel/exit.c:748
[< none >] do_group_exit+0x108/0x330 kernel/exit.c:878
[< none >] get_signal+0x5e4/0x14f0 kernel/signal.c:2307
[< none >] do_signal+0x83/0x1c90 arch/x86/kernel/signal.c:712
[< none >] exit_to_usermode_loop+0x1a5/0x210
arch/x86/entry/common.c:247
[< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:282
[< none >] syscall_return_slowpath+0x2ba/0x340
arch/x86/entry/common.c:344
[< none >] int_ret_from_sys_call+0x25/0x9f
arch/x86/entry/entry_64.S:281

And then a worker thread accessed it here:

Call Trace:
[< inline >] kasan_report mm/kasan/report.c:274
[<ffffffff81764f9e>] __asan_report_store8_noabort+0x3e/0x40
mm/kasan/report.c:300
[< inline >] debug_spin_unlock kernel/locking/spinlock_debug.c:102
[<ffffffff81466608>] do_raw_spin_unlock+0x228/0x240
kernel/locking/spinlock_debug.c:158
[< inline >] __raw_spin_unlock_irqrestore
include/linux/spinlock_api_smp.h:161
[<ffffffff86652cf7>] _raw_spin_unlock_irqrestore+0x27/0xc0
kernel/locking/spinlock.c:191
[< inline >] spin_unlock_irqrestore include/linux/spinlock.h:362
[<ffffffff8143975f>] __wake_up+0x3f/0x50 kernel/sched/wait.c:96
[<ffffffff8484b983>] vhci_send_frame+0xc3/0x100 drivers/bluetooth/hci_vhci.c:86
[<ffffffff85d38315>] hci_send_frame+0x1f5/0x310 net/bluetooth/hci_core.c:3316
[<ffffffff85d385bf>] hci_cmd_work+0x18f/0x2e0 net/bluetooth/hci_core.c:4196
[<ffffffff813a2386>] process_one_work+0x796/0x1440 kernel/workqueue.c:2037
[<ffffffff813a310b>] worker_thread+0xdb/0xfc0 kernel/workqueue.c:2171
[<ffffffff813b637f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
[<ffffffff866535ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468

So either freeing of the memory must be delayed, or the access must not happen.

[Jiri Slaby]

Scratch that, it happened on 4.4.6 today.

[Jiri Slaby]

On 03/08/2016, 07:32 PM, Marcel Holtmann wrote:
> that means very little to me actually. So is the real issue caused by opening /dev/vhci or is that theoretical one via some internal kernel compile time feature.

Hi, what do you think about this one?

--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -196,6 +196,11 @@ static inline ssize_t vhci_get_user(stru

cancel_delayed_work_sync(&data->open_timeout);

+ if (data->hdev) {
+ kfree_skb(skb);
+ return -EBADFD;
+ }
+
opcode = *((__u8 *) skb->data);
skb_pull(skb, 1);


open_timeout could be in progress (raced with us) and _sync cancel
waited for vhci_create_device to actually finish and create the device
the second time.