* [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
@ 2017-11-06 8:20 Yu Chen
2017-11-06 8:31 ` Greg KH
0 siblings, 1 reply; 8+ messages in thread
From: Yu Chen @ 2017-11-06 8:20 UTC (permalink / raw)
To: mathias.nyman, gregkh, linux-usb, linux-kernel
Cc: fanning4, lirui39, yangdi10, wangbinghui, groeck, john.stultz
From: Yu Chen <chenyu56@huawei.com>
Check vdev->real_port 0 to avoid panic
[ 9.261347] [<ffffff800884a390>] xhci_free_virt_devices_depth_first+0x58/0x108
[ 9.261352] [<ffffff800884a814>] xhci_mem_cleanup+0x1bc/0x570
[ 9.261355] [<ffffff8008842de8>] xhci_stop+0x140/0x1c8
[ 9.261365] [<ffffff80087ed304>] usb_remove_hcd+0xfc/0x1d0
[ 9.261369] [<ffffff80088551c4>] xhci_plat_remove+0x6c/0xa8
[ 9.261377] [<ffffff80086e928c>] platform_drv_remove+0x2c/0x70
[ 9.261384] [<ffffff80086e6ea0>] __device_release_driver+0x80/0x108
[ 9.261387] [<ffffff80086e7a1c>] device_release_driver+0x2c/0x40
[ 9.261392] [<ffffff80086e5f28>] bus_remove_device+0xe0/0x120
[ 9.261396] [<ffffff80086e2e34>] device_del+0x114/0x210
[ 9.261399] [<ffffff80086e9e00>] platform_device_del+0x30/0xa0
[ 9.261403] [<ffffff8008810bdc>] dwc3_otg_work+0x204/0x488
[ 9.261407] [<ffffff80088133fc>] event_work+0x304/0x5b8
[ 9.261414] [<ffffff80080e31b0>] process_one_work+0x148/0x490
[ 9.261417] [<ffffff80080e3548>] worker_thread+0x50/0x4a0
[ 9.261421] [<ffffff80080e9ea0>] kthread+0xe8/0x100
[ 9.261427] [<ffffff8008083680>] ret_from_fork+0x10/0x50
The problem can occur if xhci_plat_remove() is called shortly after
xhci_plat_probe(). While xhci_free_virt_devices_depth_first been
called before the device has been setup and get real_port initialized.
The problem occurred on Hikey960 and was reproduced by Guenter Roeck
on Kevin with chromeos-4.4.
Cc: Guenter Roeck <groeck@google.com>
Signed-off-by: Fan Ning <fanning4@hisilicon.com>
Signed-off-by: Li Rui <lirui39@hisilicon.com>
Signed-off-by: yangdi <yangdi10@hisilicon.com>
Signed-off-by: Yu Chen <chenyu56@huawei.com>
---
drivers/usb/host/xhci-mem.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 2a82c927ded2..0361b4a58f59 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -947,6 +947,9 @@ void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
if (!vdev)
return;
+ if (WARN_ON(!vdev->real_port))
+ goto out;
+
tt_list_head = &(xhci->rh_bw[vdev->real_port - 1].tts);
list_for_each_entry_safe(tt_info, next, tt_list_head, tt_list) {
/* is this a hub device that added a tt_info to the tts list */
@@ -960,6 +963,7 @@ void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
}
}
}
+out:
/* we are now at a leaf device */
xhci_free_virt_device(xhci, slot_id);
}
--
2.15.0-rc2
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
2017-11-06 8:20 [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first Yu Chen
@ 2017-11-06 8:31 ` Greg KH
2017-11-06 10:03 ` Chen Yu
0 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2017-11-06 8:31 UTC (permalink / raw)
To: Yu Chen
Cc: mathias.nyman, linux-usb, linux-kernel, fanning4, lirui39,
yangdi10, wangbinghui, groeck, john.stultz
On Mon, Nov 06, 2017 at 04:20:23PM +0800, Yu Chen wrote:
> From: Yu Chen <chenyu56@huawei.com>
>
> Check vdev->real_port 0 to avoid panic
> [ 9.261347] [<ffffff800884a390>] xhci_free_virt_devices_depth_first+0x58/0x108
> [ 9.261352] [<ffffff800884a814>] xhci_mem_cleanup+0x1bc/0x570
> [ 9.261355] [<ffffff8008842de8>] xhci_stop+0x140/0x1c8
> [ 9.261365] [<ffffff80087ed304>] usb_remove_hcd+0xfc/0x1d0
> [ 9.261369] [<ffffff80088551c4>] xhci_plat_remove+0x6c/0xa8
> [ 9.261377] [<ffffff80086e928c>] platform_drv_remove+0x2c/0x70
> [ 9.261384] [<ffffff80086e6ea0>] __device_release_driver+0x80/0x108
> [ 9.261387] [<ffffff80086e7a1c>] device_release_driver+0x2c/0x40
> [ 9.261392] [<ffffff80086e5f28>] bus_remove_device+0xe0/0x120
> [ 9.261396] [<ffffff80086e2e34>] device_del+0x114/0x210
> [ 9.261399] [<ffffff80086e9e00>] platform_device_del+0x30/0xa0
> [ 9.261403] [<ffffff8008810bdc>] dwc3_otg_work+0x204/0x488
> [ 9.261407] [<ffffff80088133fc>] event_work+0x304/0x5b8
> [ 9.261414] [<ffffff80080e31b0>] process_one_work+0x148/0x490
> [ 9.261417] [<ffffff80080e3548>] worker_thread+0x50/0x4a0
> [ 9.261421] [<ffffff80080e9ea0>] kthread+0xe8/0x100
> [ 9.261427] [<ffffff8008083680>] ret_from_fork+0x10/0x50
>
> The problem can occur if xhci_plat_remove() is called shortly after
> xhci_plat_probe(). While xhci_free_virt_devices_depth_first been
> called before the device has been setup and get real_port initialized.
> The problem occurred on Hikey960 and was reproduced by Guenter Roeck
> on Kevin with chromeos-4.4.
>
> Cc: Guenter Roeck <groeck@google.com>
> Signed-off-by: Fan Ning <fanning4@hisilicon.com>
> Signed-off-by: Li Rui <lirui39@hisilicon.com>
> Signed-off-by: yangdi <yangdi10@hisilicon.com>
> Signed-off-by: Yu Chen <chenyu56@huawei.com>
>
> ---
> drivers/usb/host/xhci-mem.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index 2a82c927ded2..0361b4a58f59 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -947,6 +947,9 @@ void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
> if (!vdev)
> return;
>
> + if (WARN_ON(!vdev->real_port))
Ok, now you are sending a lot of mess to the kernel log, so what can a
user do about it?
How can this ever happen? Is it a hardware error, or a kernel driver
logic error?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
2017-11-06 8:31 ` Greg KH
@ 2017-11-06 10:03 ` Chen Yu
2017-11-06 11:32 ` Greg KH
0 siblings, 1 reply; 8+ messages in thread
From: Chen Yu @ 2017-11-06 10:03 UTC (permalink / raw)
To: Greg KH
Cc: wangbinghui, mathias.nyman, linux-usb, linux-kernel, fanning4,
lirui39, yangdi10, groeck, john.stultz
Hi,
On 2017/11/6 16:31, Greg KH wrote:
> On Mon, Nov 06, 2017 at 04:20:23PM +0800, Yu Chen wrote:
>> From: Yu Chen <chenyu56@huawei.com>
>>
>> Check vdev->real_port 0 to avoid panic
>> [ 9.261347] [<ffffff800884a390>] xhci_free_virt_devices_depth_first+0x58/0x108
>> [ 9.261352] [<ffffff800884a814>] xhci_mem_cleanup+0x1bc/0x570
>> [ 9.261355] [<ffffff8008842de8>] xhci_stop+0x140/0x1c8
>> [ 9.261365] [<ffffff80087ed304>] usb_remove_hcd+0xfc/0x1d0
>> [ 9.261369] [<ffffff80088551c4>] xhci_plat_remove+0x6c/0xa8
>> [ 9.261377] [<ffffff80086e928c>] platform_drv_remove+0x2c/0x70
>> [ 9.261384] [<ffffff80086e6ea0>] __device_release_driver+0x80/0x108
>> [ 9.261387] [<ffffff80086e7a1c>] device_release_driver+0x2c/0x40
>> [ 9.261392] [<ffffff80086e5f28>] bus_remove_device+0xe0/0x120
>> [ 9.261396] [<ffffff80086e2e34>] device_del+0x114/0x210
>> [ 9.261399] [<ffffff80086e9e00>] platform_device_del+0x30/0xa0
>> [ 9.261403] [<ffffff8008810bdc>] dwc3_otg_work+0x204/0x488
>> [ 9.261407] [<ffffff80088133fc>] event_work+0x304/0x5b8
>> [ 9.261414] [<ffffff80080e31b0>] process_one_work+0x148/0x490
>> [ 9.261417] [<ffffff80080e3548>] worker_thread+0x50/0x4a0
>> [ 9.261421] [<ffffff80080e9ea0>] kthread+0xe8/0x100
>> [ 9.261427] [<ffffff8008083680>] ret_from_fork+0x10/0x50
>>
>> The problem can occur if xhci_plat_remove() is called shortly after
>> xhci_plat_probe(). While xhci_free_virt_devices_depth_first been
>> called before the device has been setup and get real_port initialized.
>> The problem occurred on Hikey960 and was reproduced by Guenter Roeck
>> on Kevin with chromeos-4.4.
>>
>> Cc: Guenter Roeck <groeck@google.com>
>> Signed-off-by: Fan Ning <fanning4@hisilicon.com>
>> Signed-off-by: Li Rui <lirui39@hisilicon.com>
>> Signed-off-by: yangdi <yangdi10@hisilicon.com>
>> Signed-off-by: Yu Chen <chenyu56@huawei.com>
>>
>> ---
>> drivers/usb/host/xhci-mem.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
>> index 2a82c927ded2..0361b4a58f59 100644
>> --- a/drivers/usb/host/xhci-mem.c
>> +++ b/drivers/usb/host/xhci-mem.c
>> @@ -947,6 +947,9 @@ void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
>> if (!vdev)
>> return;
>>
>> + if (WARN_ON(!vdev->real_port))
>
> Ok, now you are sending a lot of mess to the kernel log, so what can a
> user do about it?
>
> How can this ever happen? Is it a hardware error, or a kernel driver
> logic error?
>
> thanks,
>
> greg k-h
>
> .
>
The problem is a driver logic error, it can reproduced if xhci_plat_remove() is
called shortly after xhci_plat_probe() while xhci_alloc_virt_device has been called
but real_port has not been initialized in xhci_setup_addressable_virt_dev.
A simple process is as below:
xhci_plat_probe()
|
usb_add_hcd() xhci_plat_remove()
| |
find some device usb_remove_hcd()
| |
hub_port_connect() -> usb_alloc_dev() usb_disconnect()
| |
before hub_enable_device() xhci_stop()
|
xhci_mem_cleanup()
|
xhci_free_virt_devices_depth_first()
|
real_port is 0 access xhci->rh_bw[vdev->real_port-1]
The problem came from https://bugs.96boards.org/show_bug.cgi?id=535
Also look at crbug.com/700041
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
2017-11-06 10:03 ` Chen Yu
@ 2017-11-06 11:32 ` Greg KH
2017-11-06 12:36 ` Chen Yu
0 siblings, 1 reply; 8+ messages in thread
From: Greg KH @ 2017-11-06 11:32 UTC (permalink / raw)
To: Chen Yu
Cc: wangbinghui, mathias.nyman, linux-usb, linux-kernel, fanning4,
lirui39, yangdi10, groeck, john.stultz
On Mon, Nov 06, 2017 at 06:03:08PM +0800, Chen Yu wrote:
> Hi,
>
> On 2017/11/6 16:31, Greg KH wrote:
> > On Mon, Nov 06, 2017 at 04:20:23PM +0800, Yu Chen wrote:
> >> From: Yu Chen <chenyu56@huawei.com>
> >>
> >> Check vdev->real_port 0 to avoid panic
> >> [ 9.261347] [<ffffff800884a390>] xhci_free_virt_devices_depth_first+0x58/0x108
> >> [ 9.261352] [<ffffff800884a814>] xhci_mem_cleanup+0x1bc/0x570
> >> [ 9.261355] [<ffffff8008842de8>] xhci_stop+0x140/0x1c8
> >> [ 9.261365] [<ffffff80087ed304>] usb_remove_hcd+0xfc/0x1d0
> >> [ 9.261369] [<ffffff80088551c4>] xhci_plat_remove+0x6c/0xa8
> >> [ 9.261377] [<ffffff80086e928c>] platform_drv_remove+0x2c/0x70
> >> [ 9.261384] [<ffffff80086e6ea0>] __device_release_driver+0x80/0x108
> >> [ 9.261387] [<ffffff80086e7a1c>] device_release_driver+0x2c/0x40
> >> [ 9.261392] [<ffffff80086e5f28>] bus_remove_device+0xe0/0x120
> >> [ 9.261396] [<ffffff80086e2e34>] device_del+0x114/0x210
> >> [ 9.261399] [<ffffff80086e9e00>] platform_device_del+0x30/0xa0
> >> [ 9.261403] [<ffffff8008810bdc>] dwc3_otg_work+0x204/0x488
> >> [ 9.261407] [<ffffff80088133fc>] event_work+0x304/0x5b8
> >> [ 9.261414] [<ffffff80080e31b0>] process_one_work+0x148/0x490
> >> [ 9.261417] [<ffffff80080e3548>] worker_thread+0x50/0x4a0
> >> [ 9.261421] [<ffffff80080e9ea0>] kthread+0xe8/0x100
> >> [ 9.261427] [<ffffff8008083680>] ret_from_fork+0x10/0x50
> >>
> >> The problem can occur if xhci_plat_remove() is called shortly after
> >> xhci_plat_probe(). While xhci_free_virt_devices_depth_first been
> >> called before the device has been setup and get real_port initialized.
> >> The problem occurred on Hikey960 and was reproduced by Guenter Roeck
> >> on Kevin with chromeos-4.4.
> >>
> >> Cc: Guenter Roeck <groeck@google.com>
> >> Signed-off-by: Fan Ning <fanning4@hisilicon.com>
> >> Signed-off-by: Li Rui <lirui39@hisilicon.com>
> >> Signed-off-by: yangdi <yangdi10@hisilicon.com>
> >> Signed-off-by: Yu Chen <chenyu56@huawei.com>
> >>
> >> ---
> >> drivers/usb/host/xhci-mem.c | 4 ++++
> >> 1 file changed, 4 insertions(+)
> >>
> >> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> >> index 2a82c927ded2..0361b4a58f59 100644
> >> --- a/drivers/usb/host/xhci-mem.c
> >> +++ b/drivers/usb/host/xhci-mem.c
> >> @@ -947,6 +947,9 @@ void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id)
> >> if (!vdev)
> >> return;
> >>
> >> + if (WARN_ON(!vdev->real_port))
> >
> > Ok, now you are sending a lot of mess to the kernel log, so what can a
> > user do about it?
> >
> > How can this ever happen? Is it a hardware error, or a kernel driver
> > logic error?
> >
> > thanks,
> >
> > greg k-h
> >
> > .
> >
>
> The problem is a driver logic error, it can reproduced if xhci_plat_remove() is
> called shortly after xhci_plat_probe() while xhci_alloc_virt_device has been called
> but real_port has not been initialized in xhci_setup_addressable_virt_dev.
Who is calling xhci_plat_remove() like this?
> A simple process is as below:
> xhci_plat_probe()
> |
> usb_add_hcd() xhci_plat_remove()
> | |
> find some device usb_remove_hcd()
> | |
> hub_port_connect() -> usb_alloc_dev() usb_disconnect()
> | |
> before hub_enable_device() xhci_stop()
> |
> xhci_mem_cleanup()
> |
> xhci_free_virt_devices_depth_first()
> |
> real_port is 0 access xhci->rh_bw[vdev->real_port-1]
>
> The problem came from https://bugs.96boards.org/show_bug.cgi?id=535
> Also look at crbug.com/700041
Then the bug needs to be fixed, throwing a huge kernel trace message
into the kernel log is not "fixing" the problem at all, right?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
2017-11-06 11:32 ` Greg KH
@ 2017-11-06 12:36 ` Chen Yu
2017-11-06 14:00 ` Mathias Nyman
0 siblings, 1 reply; 8+ messages in thread
From: Chen Yu @ 2017-11-06 12:36 UTC (permalink / raw)
To: Greg KH
Cc: wangbinghui, mathias.nyman, linux-usb, linux-kernel, fanning4,
lirui39, yangdi10, groeck, john.stultz
On 2017/11/6 19:32, Greg KH wrote:
>> A simple process is as below:
>> xhci_plat_probe()
>> |
>> usb_add_hcd() xhci_plat_remove()
>> | |
>> find some device usb_remove_hcd()
>> | |
>> hub_port_connect() -> usb_alloc_dev() usb_disconnect()
>> | |
>> before hub_enable_device() xhci_stop()
>> |
>> xhci_mem_cleanup()
>> |
>> xhci_free_virt_devices_depth_first()
>> |
>> real_port is 0 access xhci->rh_bw[vdev->real_port-1]
>>
>> The problem came from https://bugs.96boards.org/show_bug.cgi?id=535
>> Also look at crbug.com/700041
>
> Then the bug needs to be fixed, throwing a huge kernel trace message
> into the kernel log is not "fixing" the problem at all, right?
>
> thanks,
>
> greg k-h
>
> .
>
You are right, the way that xhci_plat_remove() to be called needs to be fixed.
But there is still possibility for this crash.
What do you think if just add an "xhci_warn" instead of "WARN_ON"?
+ if (!vdev->real_port) {
+ xhci_warn(xhci, "Bad vdev->real_port\n");
+ goto out;
+ }
+
Best regards
Yu Chen
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
2017-11-06 14:00 ` Mathias Nyman
@ 2017-11-06 14:00 ` Guenter Roeck
2017-11-07 1:55 ` Chen Yu
1 sibling, 0 replies; 8+ messages in thread
From: Guenter Roeck @ 2017-11-06 14:00 UTC (permalink / raw)
To: Mathias Nyman
Cc: Chen Yu, Greg KH, wangbinghui, mathias.nyman, linux-usb,
linux-kernel, fanning4, lirui39, yangdi10, John Stultz
On Mon, Nov 6, 2017 at 6:00 AM, Mathias Nyman
<mathias.nyman@linux.intel.com> wrote:
> On 06.11.2017 14:36, Chen Yu wrote:
>>
>>
>>
>> On 2017/11/6 19:32, Greg KH wrote:
>>>>
>>>> A simple process is as below:
>>>> xhci_plat_probe()
>>>> |
>>>> usb_add_hcd()
>>>> xhci_plat_remove()
>>>> | |
>>>> find some device usb_remove_hcd()
>>>> | |
>>>> hub_port_connect() -> usb_alloc_dev() usb_disconnect()
>>>> | |
>>>> before hub_enable_device() xhci_stop()
>>>> |
>>>>
>>>> xhci_mem_cleanup()
>>>> |
>>>>
>>>> xhci_free_virt_devices_depth_first()
>>>> |
>>>> real_port is 0
>>>> access xhci->rh_bw[vdev->real_port-1]
>>>>
>>>> The problem came from https://bugs.96boards.org/show_bug.cgi?id=535
>>>> Also look at crbug.com/700041
>>>
>>>
>>> Then the bug needs to be fixed, throwing a huge kernel trace message
>>> into the kernel log is not "fixing" the problem at all, right?
>>>
>>> thanks,
>>>
>>> greg k-h
>>>
>>> .
>>>
>>
>> You are right, the way that xhci_plat_remove() to be called needs to be
>> fixed.
>> But there is still possibility for this crash.
>> What do you think if just add an "xhci_warn" instead of "WARN_ON"?
>> + if (!vdev->real_port) {
>> + xhci_warn(xhci, "Bad vdev->real_port\n");
>> + goto out;
>> + }
>> +
>>
>
> This patch solves the issue, just drop all the error messages.
>
> vdev->real_port is not set until the the device enable/address
> stage, and we know it won't have any children yet then, so no need to
> worry about a child having tt pointers to this device.
>
> The "goto out" to xhci_free_virt_device() you do is fine here.
>
> xhci_plat_remove() is the .remove callback for the xhci platform driver.
> It might get called before a device is properly enabled/addressed.
> Not really a error. A unlikely but possible situation.
>
Agreed. I can reproduce the problem with a well timed bind/unbind loop.
Guenter
> xhci_free_tt_info() already has a similar check
>
> Thanks
> -Mathias
>
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
2017-11-06 12:36 ` Chen Yu
@ 2017-11-06 14:00 ` Mathias Nyman
2017-11-06 14:00 ` Guenter Roeck
2017-11-07 1:55 ` Chen Yu
0 siblings, 2 replies; 8+ messages in thread
From: Mathias Nyman @ 2017-11-06 14:00 UTC (permalink / raw)
To: Chen Yu, Greg KH
Cc: wangbinghui, mathias.nyman, linux-usb, linux-kernel, fanning4,
lirui39, yangdi10, groeck, john.stultz
On 06.11.2017 14:36, Chen Yu wrote:
>
>
> On 2017/11/6 19:32, Greg KH wrote:
>>> A simple process is as below:
>>> xhci_plat_probe()
>>> |
>>> usb_add_hcd() xhci_plat_remove()
>>> | |
>>> find some device usb_remove_hcd()
>>> | |
>>> hub_port_connect() -> usb_alloc_dev() usb_disconnect()
>>> | |
>>> before hub_enable_device() xhci_stop()
>>> |
>>> xhci_mem_cleanup()
>>> |
>>> xhci_free_virt_devices_depth_first()
>>> |
>>> real_port is 0 access xhci->rh_bw[vdev->real_port-1]
>>>
>>> The problem came from https://bugs.96boards.org/show_bug.cgi?id=535
>>> Also look at crbug.com/700041
>>
>> Then the bug needs to be fixed, throwing a huge kernel trace message
>> into the kernel log is not "fixing" the problem at all, right?
>>
>> thanks,
>>
>> greg k-h
>>
>> .
>>
>
> You are right, the way that xhci_plat_remove() to be called needs to be fixed.
> But there is still possibility for this crash.
> What do you think if just add an "xhci_warn" instead of "WARN_ON"?
> + if (!vdev->real_port) {
> + xhci_warn(xhci, "Bad vdev->real_port\n");
> + goto out;
> + }
> +
>
This patch solves the issue, just drop all the error messages.
vdev->real_port is not set until the the device enable/address
stage, and we know it won't have any children yet then, so no need to
worry about a child having tt pointers to this device.
The "goto out" to xhci_free_virt_device() you do is fine here.
xhci_plat_remove() is the .remove callback for the xhci platform driver.
It might get called before a device is properly enabled/addressed.
Not really a error. A unlikely but possible situation.
xhci_free_tt_info() already has a similar check
Thanks
-Mathias
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first
2017-11-06 14:00 ` Mathias Nyman
2017-11-06 14:00 ` Guenter Roeck
@ 2017-11-07 1:55 ` Chen Yu
1 sibling, 0 replies; 8+ messages in thread
From: Chen Yu @ 2017-11-07 1:55 UTC (permalink / raw)
To: Mathias Nyman, Greg KH
Cc: wangbinghui, mathias.nyman, linux-usb, linux-kernel, fanning4,
lirui39, yangdi10, groeck, john.stultz
On 2017/11/6 22:00, Mathias Nyman wrote:
> On 06.11.2017 14:36, Chen Yu wrote:
>>
>>
>> On 2017/11/6 19:32, Greg KH wrote:
>>>> A simple process is as below:
>>>> xhci_plat_probe()
>>>> |
>>>> usb_add_hcd() xhci_plat_remove()
>>>> | |
>>>> find some device usb_remove_hcd()
>>>> | |
>>>> hub_port_connect() -> usb_alloc_dev() usb_disconnect()
>>>> | |
>>>> before hub_enable_device() xhci_stop()
>>>> |
>>>> xhci_mem_cleanup()
>>>> |
>>>> xhci_free_virt_devices_depth_first()
>>>> |
>>>> real_port is 0 access xhci->rh_bw[vdev->real_port-1]
>>>>
>>>> The problem came from https://bugs.96boards.org/show_bug.cgi?id=535
>>>> Also look at crbug.com/700041
>>>
>>> Then the bug needs to be fixed, throwing a huge kernel trace message
>>> into the kernel log is not "fixing" the problem at all, right?
>>>
>>> thanks,
>>>
>>> greg k-h
>>>
>>> .
>>>
>>
>> You are right, the way that xhci_plat_remove() to be called needs to be fixed.
>> But there is still possibility for this crash.
>> What do you think if just add an "xhci_warn" instead of "WARN_ON"?
>> + if (!vdev->real_port) {
>> + xhci_warn(xhci, "Bad vdev->real_port\n");
>> + goto out;
>> + }
>> +
>>
>
> This patch solves the issue, just drop all the error messages.
>
> vdev->real_port is not set until the the device enable/address
> stage, and we know it won't have any children yet then, so no need to
> worry about a child having tt pointers to this device.
>
> The "goto out" to xhci_free_virt_device() you do is fine here.
>
> xhci_plat_remove() is the .remove callback for the xhci platform driver.
> It might get called before a device is properly enabled/addressed.
> Not really a error. A unlikely but possible situation.
>
> xhci_free_tt_info() already has a similar check
Thanks a lot for your analysis and suggestion!
The check within xhci_free_tt_info() is a better one.
I will upload a new patch like the check in xhci_free_tt_info().
>
> Thanks
> -Mathias
>
>
> .
>
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2017-11-07 1:57 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-11-06 8:20 [PATCH v2] usb:xhci fix panic in xhci_free_virt_devices_depth_first Yu Chen
2017-11-06 8:31 ` Greg KH
2017-11-06 10:03 ` Chen Yu
2017-11-06 11:32 ` Greg KH
2017-11-06 12:36 ` Chen Yu
2017-11-06 14:00 ` Mathias Nyman
2017-11-06 14:00 ` Guenter Roeck
2017-11-07 1:55 ` Chen Yu
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