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SubjectRe: [PATCH] au0828: fix use-after-free at USB probing

Quoting Andrey Konovalov <andreyknvl@google.com>:

> On Fri, Nov 10, 2017 at 1:21 AM, Gustavo A. R. Silva
> <garsilva@embeddedor.com> wrote:
>> Hi Andrey,
>>
>> Could you please try this patch?
>>
>> Thank you
>
> Hi Gustavo,
>
> With your patch I get a different crash. Not sure if it's another bug
> or the same one manifesting differently.
>

That's the same one. It seems that the best solution is to remove the
kfree after the mutex_unlock and let the device resources be freed in
au0828_usb_disconnect.

Please try the following patch instead.

I appreciate your help.

Thank you, Andrey.

---
drivers/media/usb/au0828/au0828-core.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/drivers/media/usb/au0828/au0828-core.c
b/drivers/media/usb/au0828/au0828-core.c
index cd363a2..257ae0d 100644
--- a/drivers/media/usb/au0828/au0828-core.c
+++ b/drivers/media/usb/au0828/au0828-core.c
@@ -629,7 +629,6 @@ static int au0828_usb_probe(struct usb_interface
*interface,
pr_err("%s() au0282_dev_register failed to register
on V4L2\n",
__func__);
mutex_unlock(&dev->lock);
- kfree(dev);
goto done;
}

--
2.7.4
> au0828: recv_control_msg() Failed receiving control message, error -71.
> au0828: recv_control_msg() Failed receiving control message, error -71.
> au8522_writereg: writereg error (reg == 0x106, val == 0x0001, ret == -5)
> usb 1-1: selecting invalid altsetting 5
> au0828: Failure setting usb interface0 to as5
> au0828: au0828_usb_probe() au0282_dev_register failed to register on V4L2
> au0828: probe of 1-1:0.0 failed with error -22
> usb 1-1: USB disconnect, device number 2
> ==================================================================
> BUG: KASAN: use-after-free in __list_del_entry_valid+0xda/0xf3
> Read of size 8 at addr ffff8800641d0410 by task kworker/0:1/24
>
> CPU: 0 PID: 24 Comm: kworker/0:1 Not tainted
> 4.14.0-rc5-43687-g72e555fa3d2e-dirty #105
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
> __dump_stack lib/dump_stack.c:16
> dump_stack+0xc1/0x11f lib/dump_stack.c:52
> print_address_description+0x71/0x234 mm/kasan/report.c:252
> kasan_report_error mm/kasan/report.c:351
> kasan_report+0x173/0x270 mm/kasan/report.c:409
> __asan_report_load8_noabort+0x19/0x20 mm/kasan/report.c:430
> __list_del_entry_valid+0xda/0xf3 lib/list_debug.c:54
> __list_del_entry ./include/linux/list.h:116
> list_del_init ./include/linux/list.h:158
> device_pm_remove+0x4a/0x1da drivers/base/power/main.c:149
> device_del+0x55f/0xa30 drivers/base/core.c:1986
> usb_disable_device+0x1df/0x670 drivers/usb/core/message.c:1170
> usb_disconnect+0x260/0x7a0 drivers/usb/core/hub.c:2124
> hub_port_connect drivers/usb/core/hub.c:4754
> hub_port_connect_change drivers/usb/core/hub.c:5009
> port_event drivers/usb/core/hub.c:5115
> hub_event+0xe09/0x2eb0 drivers/usb/core/hub.c:5195
> process_one_work+0x86d/0x13e0 kernel/workqueue.c:2119
> process_scheduled_works kernel/workqueue.c:2179
> worker_thread+0x689/0xea0 kernel/workqueue.c:2255
> kthread+0x334/0x400 kernel/kthread.c:231
> ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431
>
> The buggy address belongs to the page:
> page:ffffea0001907400 count:0 mapcount:-127 mapping: (null)
> index:0x0
> flags: 0x100000000000000()
> raw: 0100000000000000 0000000000000000 0000000000000000 00000000ffffff80
> raw: ffffea00018a8f20 ffff88007fffa690 0000000000000002 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff8800641d0300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ffff8800641d0380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>> ffff8800641d0400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ^
> ffff8800641d0480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ffff8800641d0500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ==================================================================
>
> Thanks!
>
>>
>>
>> The device is typically freed on failure after trying to set
>> USB interface0 to as5 in function au0828_analog_register.
>>
>> Fix use-after-free by returning the error value inmediately
>> after failure, instead of jumping to au0828_usb_disconnect
>> where _dev_ is also freed.
>>
>> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
>> ---
>> drivers/media/usb/au0828/au0828-core.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/media/usb/au0828/au0828-core.c
>> b/drivers/media/usb/au0828/au0828-core.c
>> index cd363a2..b4abd90 100644
>> --- a/drivers/media/usb/au0828/au0828-core.c
>> +++ b/drivers/media/usb/au0828/au0828-core.c
>> @@ -630,7 +630,7 @@ static int au0828_usb_probe(struct
>> usb_interface *interface,
>> __func__);
>> mutex_unlock(&dev->lock);
>> kfree(dev);
>> - goto done;
>> + return retval;
>> }
>>
>> /* Digital TV */
>> @@ -655,7 +655,6 @@ static int au0828_usb_probe(struct
>> usb_interface *interface,
>>
>> retval = au0828_media_device_register(dev, usbdev);
>>
>> -done:
>> if (retval < 0)
>> au0828_usb_disconnect(interface);
>>
>> --
>> 2.7.4
>>






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