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SubjectRe: NULL pointer dereference when writing fuzzed data to /dev/uhid
Hi Anatoly,


On Fri, Jan 4, 2019 at 1:32 PM Anatoly Trosinenko
<anatoly.trosinenko@gmail.com> wrote:
>
> Hello,
>
> When writing the attached file to /dev/uhid, a NULL dereference occurs
> in kernel. As I understand, the problem is not UHID-specific, but is
> related to HID subsystem.

Thanks for the report.
I wanted to tell you that I started investigating the other private
report you sent us, but couldn't find the time to properly come with a
fix as the fuzzed data is hard to discriminate from valid data.

A couple of notes though:
- writing to uhid needs to be done by root. Any distribution that
doesn't enforce that is doomed to have several security issues
- we could somehow reproduce those fuzzed data on a USB or Bluetooth
connection, but that would require physical access to the device, so
you are doomed also
- last IIRC, there was some attempts by the ChromeOS team to allow
access to the HID stack from the Chrome plugins, I don't know if this
is able to generate the issues.

On the specifics reported here:

>
> How to reproduce:
> 1) Checkout the fresh master branch of the Linux kernel (tested on
> commit 96d4f267e)
> 2) Compile it with the attached config (kvm-xfstests capable)
> 3) Take one of reproducers and execute
> cat /vtmp/repro > /dev/uhid
>
> What happens:
>
> For chicony.bin:
>
> root@kvm-xfstests:~# cat /vtmp/chicony.bin > /dev/uhid
> [ 19.072703] BUG: unable to handle kernel NULL pointer dereference
> at 0000000000000002
> [ 19.073371] #PF error: [normal kernel read fault]
> [ 19.073755] PGD 8000000078b2c067 P4D 8000000078b2c067 PUD 0
> [ 19.074223] Oops: 0000 [#1] SMP PTI
> [ 19.074809] CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted
> 4.20.0-xfstests-10979-g96d4f267e40 #1
> [ 19.075965] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.11.1-1ubuntu1 04/01/2014
> [ 19.077599] Workqueue: events uhid_device_add_worker
> [ 19.078019] RIP: 0010:ch_switch12_report_fixup+0x13/0x70

This driver expects the device to be connected on USB, and you are
triggering the oops because you are on uhid.
I am chasing the USB dependencies in most drivers, but this is a hard
task to do when I do not have access to the actual devices.

I guess one way of fixing that is to add a check for the actual
transport driver during probe:
hid_is_using_ll_driver(hdev, &usb_hid_driver)

Patches are welcome :)

> [ 19.078462] Code: 49 8b 00 3e 80 60 20 df b8 01 00 00 00 c3 66 0f
> 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8b 8f 48 19 00 00 48 89 f0 48
> 8b 49 d8 <80> 79 02 01 74 01 c3 81 7f 3c 21 14 00 00 75 f6 83 3a 7f 76
> f1 80
> [ 19.080103] RSP: 0018:ffffa1d880367c48 EFLAGS: 00010286
> [ 19.080541] RAX: ffff9b653d27b180 RBX: ffff9b653a6fb948 RCX: 0000000000000000
> [ 19.081133] RDX: ffffa1d880367c5c RSI: ffff9b653d27b180 RDI: ffff9b653a6fa000
> [ 19.081780] RBP: ffff9b653d27b180 R08: 000000064992eed0 R09: 0000000000000000
> [ 19.082409] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9b653a6fa000
> [ 19.083017] R13: ffffffff83f14510 R14: ffffffff83f14440 R15: 0000000000000000
> [ 19.083619] FS: 0000000000000000(0000) GS:ffff9b653fc00000(0000)
> knlGS:0000000000000000
> [ 19.084362] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 19.085164] CR2: 0000000000000002 CR3: 00000000788b8004 CR4: 0000000000360ef0
> [ 19.085789] Call Trace:
> [ 19.086011] hid_open_report+0x81/0x2c0
> [ 19.086341] hid_device_probe+0x135/0x160
> [ 19.086754] ? __driver_attach+0x110/0x110
> [ 19.087109] really_probe+0xe0/0x390
> [ 19.087411] ? __driver_attach+0x110/0x110
> [ 19.087782] bus_for_each_drv+0x78/0xc0
> [ 19.088134] __device_attach+0xcc/0x130
> [ 19.088477] bus_probe_device+0x9f/0xb0
> [ 19.088832] device_add+0x422/0x680
> [ 19.089144] ? __debugfs_create_file+0xb5/0xf0
> [ 19.089536] hid_add_device+0xec/0x280
> [ 19.089880] uhid_device_add_worker+0x15/0x60
> [ 19.090270] process_one_work+0x238/0x5d0
> [ 19.090627] worker_thread+0x3d/0x390
> [ 19.090959] ? process_one_work+0x5d0/0x5d0
> [ 19.091331] kthread+0x121/0x140
> [ 19.096732] ? __kthread_create_on_node+0x1a0/0x1a0
> [ 19.097164] ret_from_fork+0x3a/0x50
> [ 19.097483] CR2: 0000000000000002
> [ 19.097779] ---[ end trace 1b547acaae113039 ]---
> [ 19.098186] RIP: 0010:ch_switch12_report_fixup+0x13/0x70
> [ 19.098621] Code: 49 8b 00 3e 80 60 20 df b8 01 00 00 00 c3 66 0f
> 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8b 8f 48 19 00 00 48 89 f0 48
> 8b 49 d8 <80> 79 02 01 74 01 c3 81 7f 3c 21 14 00 00 75 f6 83 3a 7f 76
> f1 80
> [ 19.100251] RSP: 0018:ffffa1d880367c48 EFLAGS: 00010286
> [ 19.100707] RAX: ffff9b653d27b180 RBX: ffff9b653a6fb948 RCX: 0000000000000000
> [ 19.101321] RDX: ffffa1d880367c5c RSI: ffff9b653d27b180 RDI: ffff9b653a6fa000
> [ 19.102448] RBP: ffff9b653d27b180 R08: 000000064992eed0 R09: 0000000000000000
> [ 19.103029] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9b653a6fa000
> [ 19.103601] R13: ffffffff83f14510 R14: ffffffff83f14440 R15: 0000000000000000
> [ 19.104173] FS: 0000000000000000(0000) GS:ffff9b653fc00000(0000)
> knlGS:0000000000000000
> [ 19.104823] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 19.105289] CR2: 0000000000000002 CR3: 00000000788b8004 CR4: 0000000000360ef0
> [ 19.105864] BUG: sleeping function called from invalid context at
> include/linux/percpu-rwsem.h:34
> [ 19.106578] in_atomic(): 0, irqs_disabled(): 1, pid: 5, name: kworker/0:0
> [ 19.107671] INFO: lockdep is turned off.
> [ 19.108384] irq event stamp: 3576
> [ 19.108976] hardirqs last enabled at (3575): [<ffffffff82e01ed5>]
> __kmalloc_track_caller+0x185/0x310
> [ 19.112970] hardirqs last disabled at (3576): [<ffffffff82c015f4>]
> trace_hardirqs_off_thunk+0x1a/0x1c
> [ 19.114557] softirqs last enabled at (3504): [<ffffffff834002b1>]
> peernet2id+0x51/0x80
> [ 19.115897] softirqs last disabled at (3502): [<ffffffff83400292>]
> peernet2id+0x32/0x80
> [ 19.117319] CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G D
> 4.20.0-xfstests-10979-g96d4f267e40 #1
> [ 19.118739] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.11.1-1ubuntu1 04/01/2014
> [ 19.120049] Workqueue: events uhid_device_add_worker
> [ 19.120767] Call Trace:
> [ 19.121127] dump_stack+0x67/0x90
> [ 19.121622] ___might_sleep.cold.13+0x9f/0xaf
> [ 19.122278] exit_signals+0x1c/0x200
> [ 19.122792] do_exit+0xac/0xaf0
> [ 19.123619] ? process_one_work+0x5d0/0x5d0
> [ 19.124520] ? kthread+0x121/0x140
> [ 19.125050] rewind_stack_do_exit+0x17/0x20
>
> For sony.bin:
>
> root@kvm-xfstests:~# cat /vtmp/sony.bin > /dev/uhid
> [ 16.891931] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.892432] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.892894] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.893362] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.893844] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.895389] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.898165] sony 0003:054C:1000.0001: ignoring exceeding usage max
> [ 16.901190] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.903797] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.906401] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.908957] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.911449] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.913936] sony 0003:054C:1000.0001: unknown main item tag 0x1
> [ 16.916551] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.918454] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.919743] sony 0003:054C:1000.0001: unknown main item tag 0x4
> [ 16.920834] sony 0003:054C:1000.0001: unknown main item tag 0xe
> [ 16.921904] sony 0003:054C:1000.0001: unknown main item tag 0xe
> [ 16.923006] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.924082] sony 0003:054C:1000.0001: unknown main item tag 0x2
> [ 16.925195] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.926289] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.927400] sony 0003:054C:1000.0001: unknown main item tag 0x0
> [ 16.928546] BUG: unable to handle kernel NULL pointer dereference
> at 0000000000000028
> [ 16.929951] #PF error: [normal kernel read fault]
> [ 16.930884] PGD 800000007a52b067 P4D 800000007a52b067 PUD 0
> [ 16.931836] Oops: 0000 [#1] SMP PTI
> [ 16.932437] CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted
> 4.20.0-xfstests-10979-g96d4f267e40 #1
> [ 16.933752] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.11.1-1ubuntu1 04/01/2014
> [ 16.935372] Workqueue: events uhid_device_add_worker
> [ 16.936321] RIP: 0010:hid_validate_values+0x48/0x110

In a sense, it's good to have a fault there because this was added to
make sure we do not blindly accept any data. The fact that it doesn't
fail gracefully is a sign that there is something else.
Maybe Roderick could have a look?

Cheers,
Benjamin

> [ 16.937690] Code: 4c 69 ce 03 01 00 00 4a 8d 44 08 0c 48 8b 44 c7
> 08 48 85 c0 0f 84 a9 00 00 00 39 88 30 08 00 00 76 53 41 89 c9 4e 8b
> 4c c8 30 <45> 39 41 28 72 69 48 83 c4 08 c3 89 f6 48 69 c6 18 08 00 00
> 48 8b
> [ 16.941067] RSP: 0018:ffffb2c880367ab0 EFLAGS: 00010286
> [ 16.941935] RAX: ffff8d54b881c870 RBX: ffff8d54b881dd08 RCX: 0000000000000000
> [ 16.943203] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8d54b881c000
> [ 16.945406] RBP: ffff8d54bacb3580 R08: 0000000000000007 R09: 0000000000000000
> [ 16.946590] R10: 0000000000000000 R11: ffff8d54b80293e6 R12: ffff8d54b881c000
> [ 16.947668] R13: dead000000000100 R14: ffff8d54b881c000 R15: ffff8d54ba4fb818
> [ 16.948765] FS: 0000000000000000(0000) GS:ffff8d54bfc00000(0000)
> knlGS:0000000000000000
> [ 16.949838] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 16.950663] CR2: 0000000000000028 CR3: 000000007a4e8002 CR4: 0000000000360ef0
> [ 16.951513] Call Trace:
> [ 16.951870] sony_input_configured+0xd6d/0x1060
> [ 16.952608] ? kobject_set_name_vargs+0x6f/0x90
> [ 16.953257] ? dev_set_name+0x57/0x70
> [ 16.953783] ? init_timer_key+0xed/0x120
> [ 16.954353] hidinput_connect+0x2fb/0x89b
> [ 16.954974] hid_connect+0x2f3/0x370
> [ 16.955489] hid_hw_start+0x38/0x60
> [ 16.956052] sony_probe+0xba/0x160
> [ 16.956541] hid_device_probe+0xf7/0x160
> [ 16.957103] ? __driver_attach+0x110/0x110
> [ 16.957689] really_probe+0xe0/0x390
> [ 16.958206] ? __driver_attach+0x110/0x110
> [ 16.958797] bus_for_each_drv+0x78/0xc0
> [ 16.959290] __device_attach+0xcc/0x130
> [ 16.959832] bus_probe_device+0x9f/0xb0
> [ 16.960407] device_add+0x422/0x680
> [ 16.960772] ? __debugfs_create_file+0xb5/0xf0
> [ 16.962459] hid_add_device+0xec/0x280
> [ 16.963517] uhid_device_add_worker+0x15/0x60
> [ 16.964304] process_one_work+0x238/0x5d0
> [ 16.965062] worker_thread+0x3d/0x390
> [ 16.965737] ? process_one_work+0x5d0/0x5d0
> [ 16.966499] kthread+0x121/0x140
> [ 16.967089] ? __kthread_create_on_node+0x1a0/0x1a0
> [ 16.967988] ret_from_fork+0x3a/0x50
> [ 16.968742] CR2: 0000000000000028
> [ 16.969394] ---[ end trace bc79f619177a8c3e ]---
> [ 16.970267] RIP: 0010:hid_validate_values+0x48/0x110
> [ 16.971167] Code: 4c 69 ce 03 01 00 00 4a 8d 44 08 0c 48 8b 44 c7
> 08 48 85 c0 0f 84 a9 00 00 00 39 88 30 08 00 00 76 53 41 89 c9 4e 8b
> 4c c8 30 <45> 39 41 28 72 69 48 83 c4 08 c3 89 f6 48 69 c6 18 08 00 00
> 48 8b
> [ 16.974023] RSP: 0018:ffffb2c880367ab0 EFLAGS: 00010286
> [ 16.974805] RAX: ffff8d54b881c870 RBX: ffff8d54b881dd08 RCX: 0000000000000000
> [ 16.975925] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8d54b881c000
> [ 16.977035] RBP: ffff8d54bacb3580 R08: 0000000000000007 R09: 0000000000000000
> [ 16.978269] R10: 0000000000000000 R11: ffff8d54b80293e6 R12: ffff8d54b881c000
> [ 16.979446] R13: dead000000000100 R14: ffff8d54b881c000 R15: ffff8d54ba4fb818
> [ 16.980503] FS: 0000000000000000(0000) GS:ffff8d54bfc00000(0000)
> knlGS:0000000000000000
> [ 16.981675] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 16.982566] CR2: 0000000000000028 CR3: 000000007a4e8002 CR4: 0000000000360ef0
> [ 16.983712] BUG: sleeping function called from invalid context at
> include/linux/percpu-rwsem.h:34
> [ 16.985362] in_atomic(): 0, irqs_disabled(): 1, pid: 5, name: kworker/0:0
> [ 16.985947] INFO: lockdep is turned off.
> [ 16.986296] irq event stamp: 4040
> [ 16.986584] hardirqs last enabled at (4039): [<ffffffffab201ed5>]
> __kmalloc_track_caller+0x185/0x310
> [ 16.987354] hardirqs last disabled at (4040): [<ffffffffab0015f4>]
> trace_hardirqs_off_thunk+0x1a/0x1c
> [ 16.988522] softirqs last enabled at (3962): [<ffffffffabc0032f>]
> __do_softirq+0x32f/0x440
> [ 16.989788] softirqs last disabled at (3955): [<ffffffffab0b32f6>]
> irq_exit+0xa6/0xe0
> [ 16.992028] CPU: 0 PID: 5 Comm: kworker/0:0 Tainted: G D
> 4.20.0-xfstests-10979-g96d4f267e40 #1
> [ 16.993354] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.11.1-1ubuntu1 04/01/2014
> [ 16.994960] Workqueue: events uhid_device_add_worker
> [ 16.996048] Call Trace:
> [ 16.996593] dump_stack+0x67/0x90
> [ 16.997203] ___might_sleep.cold.13+0x9f/0xaf
> [ 16.998004] exit_signals+0x1c/0x200
> [ 16.998660] do_exit+0xac/0xaf0
> [ 16.999232] ? process_one_work+0x5d0/0x5d0
> [ 16.999987] ? kthread+0x121/0x140
> [ 17.000709] rewind_stack_do_exit+0x17/0x20
>
>
> Best regards
> Anatoly

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