* [PATCH v2] usb: Add a lock when freeing data in usbtmc_disconnect
@ 2021-03-23 9:28 Lv Yunlong
2021-03-23 9:44 ` Greg KH
0 siblings, 1 reply; 3+ messages in thread
From: Lv Yunlong @ 2021-03-23 9:28 UTC (permalink / raw)
To: gregkh, linux-usb; +Cc: linux-kernel, Lv Yunlong
In usbtmc_disconnect, data is got from intf with the initial reference.
There is no refcount inc operation before usbmc_free_int(data). In
usbmc_free_int(data), the data may be freed.
But later in usbtmc_disconnect, there is another put function of data.
It could cause errors in race.
My patch adds a lock to protect kref from changing in race.
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
drivers/usb/class/usbtmc.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 74d5a9c5238a..44f1fcabbb1e 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -2493,8 +2493,13 @@ static void usbtmc_disconnect(struct usb_interface *intf)
usb_scuttle_anchored_urbs(&file_data->in_anchor);
}
mutex_unlock(&data->io_mutex);
+
+ spinlock_t *dev_lock = &data->dev_lock;
+
+ spin_lock_irq(dev_lock);
usbtmc_free_int(data);
kref_put(&data->kref, usbtmc_delete);
+ spin_unlock_irq(dev_lock);
}
static void usbtmc_draw_down(struct usbtmc_file_data *file_data)
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] usb: Add a lock when freeing data in usbtmc_disconnect
2021-03-23 9:28 [PATCH v2] usb: Add a lock when freeing data in usbtmc_disconnect Lv Yunlong
@ 2021-03-23 9:44 ` Greg KH
0 siblings, 0 replies; 3+ messages in thread
From: Greg KH @ 2021-03-23 9:44 UTC (permalink / raw)
To: Lv Yunlong; +Cc: linux-usb, linux-kernel
On Tue, Mar 23, 2021 at 02:28:54AM -0700, Lv Yunlong wrote:
> In usbtmc_disconnect, data is got from intf with the initial reference.
> There is no refcount inc operation before usbmc_free_int(data). In
> usbmc_free_int(data), the data may be freed.
>
> But later in usbtmc_disconnect, there is another put function of data.
> It could cause errors in race.
>
> My patch adds a lock to protect kref from changing in race.
>
> Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
> ---
> drivers/usb/class/usbtmc.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
> index 74d5a9c5238a..44f1fcabbb1e 100644
> --- a/drivers/usb/class/usbtmc.c
> +++ b/drivers/usb/class/usbtmc.c
> @@ -2493,8 +2493,13 @@ static void usbtmc_disconnect(struct usb_interface *intf)
> usb_scuttle_anchored_urbs(&file_data->in_anchor);
> }
> mutex_unlock(&data->io_mutex);
> +
> + spinlock_t *dev_lock = &data->dev_lock;
> +
> + spin_lock_irq(dev_lock);
> usbtmc_free_int(data);
> kref_put(&data->kref, usbtmc_delete);
> + spin_unlock_irq(dev_lock);
> }
>
> static void usbtmc_draw_down(struct usbtmc_file_data *file_data)
> --
> 2.25.1
You obviously did not even build this patch, let alone test it :(
Please do not waste maintainer's time by not doing the proper steps when
submitting patches.
thanks,
greg k-h
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] usb: Add a lock when freeing data in usbtmc_disconnect
[not found] <91ca594b3f434040a54485339c0e320f@rohde-schwarz.com>
@ 2021-04-14 15:10 ` guido
0 siblings, 0 replies; 3+ messages in thread
From: guido @ 2021-04-14 15:10 UTC (permalink / raw)
To: dpenkler; +Cc: linux-usb, lyl2019, guido.kiener, gregkh
Hi Dave,
I just found this patch, which does not seem to be a correct solution
to solve a race.
Maybe there is really an issue with the refcounting of data->kref, but
currently I do
not have time to check this in home office.
At least I see a problem in usbtmc_probe()
After calling:
/* Protect interrupt in endpoint data until iin_urb is freed */
kref_get(&data->kref);
the refcounter is incremented again and if usbtmc_probe() fails, the
counter is
only decremented with a single kref_put(..).
I don't know if this is the reason of Lv Yunglong's problem, but let
me know if
you have time to track down this issue, and we will work on a correct
and tested
patch.
Regards,
Guido
> -----Original Message-----
> From: Greg KH
> Sent: Tuesday, March 23, 2021 10:44 AM
> To: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
> Cc: linux-usb@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v2] usb: Add a lock when freeing data in
> usbtmc_disconnect
>
> On Tue, Mar 23, 2021 at 02:28:54AM -0700, Lv Yunlong wrote:
>> In usbtmc_disconnect, data is got from intf with the initial reference.
>> There is no refcount inc operation before usbmc_free_int(data). In
>> usbmc_free_int(data), the data may be freed.
>>
>> But later in usbtmc_disconnect, there is another put function of data.
>> It could cause errors in race.
>>
>> My patch adds a lock to protect kref from changing in race.
>>
>> Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
>> ---
>> drivers/usb/class/usbtmc.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
>> index 74d5a9c5238a..44f1fcabbb1e 100644
>> --- a/drivers/usb/class/usbtmc.c
>> +++ b/drivers/usb/class/usbtmc.c
>> @@ -2493,8 +2493,13 @@ static void usbtmc_disconnect(struct
>> usb_interface *intf)
>> usb_scuttle_anchored_urbs(&file_data->in_anchor);
>> }
>> mutex_unlock(&data->io_mutex);
>> +
>> + spinlock_t *dev_lock = &data->dev_lock;
>> +
>> + spin_lock_irq(dev_lock);
>> usbtmc_free_int(data);
>> kref_put(&data->kref, usbtmc_delete);
>> + spin_unlock_irq(dev_lock);
>> }
>>
>> static void usbtmc_draw_down(struct usbtmc_file_data *file_data)
>> --
>> 2.25.1
>
> You obviously did not even build this patch, let alone test it :(
>
> Please do not waste maintainer's time by not doing the proper steps
> when submitting patches.
>
> thanks,
>
> greg k-h
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-03-23 9:28 [PATCH v2] usb: Add a lock when freeing data in usbtmc_disconnect Lv Yunlong
2021-03-23 9:44 ` Greg KH
[not found] <91ca594b3f434040a54485339c0e320f@rohde-schwarz.com>
2021-04-14 15:10 ` guido
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