[PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around

[PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around

[Mitchel Humpherys]

There are certain client bugs (double unmap, for example) that can cause
the handle->kmap_cnt (an unsigned int) to wrap around from zero. This
causes problems when the handle is destroyed because we have:

        while (handle->kmap_cnt)
                ion_handle_kmap_put(handle);

which takes a long time to complete when kmap_cnt starts at ~0 and can
result in a watchdog timeout.

WARN and bail when kmap_cnt is about to wrap around from zero.

Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
---
 drivers/staging/android/ion/ion.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 3d5bf14722..f55f61a4cc 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -626,6 +626,10 @@ static void ion_handle_kmap_put(struct ion_handle *handle)
 {
 	struct ion_buffer *buffer = handle->buffer;
 
+	if (!handle->kmap_cnt) {
+		WARN(1, "%s: Double unmap detected! bailing...\n", __func__);
+		return;
+	}
 	handle->kmap_cnt--;
 	if (!handle->kmap_cnt)
 		ion_buffer_kmap_put(buffer);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

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Re: [PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around

[Colin Cross]

On Thu, May 22, 2014 at 5:51 PM, Mitchel Humpherys
<mitchelh@codeaurora.org> wrote:
> There are certain client bugs (double unmap, for example) that can cause
> the handle->kmap_cnt (an unsigned int) to wrap around from zero. This
> causes problems when the handle is destroyed because we have:
>
>         while (handle->kmap_cnt)
>                 ion_handle_kmap_put(handle);
>
> which takes a long time to complete when kmap_cnt starts at ~0 and can
> result in a watchdog timeout.
>
> WARN and bail when kmap_cnt is about to wrap around from zero.
>
> Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
> ---
>  drivers/staging/android/ion/ion.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> index 3d5bf14722..f55f61a4cc 100644
> --- a/drivers/staging/android/ion/ion.c
> +++ b/drivers/staging/android/ion/ion.c
> @@ -626,6 +626,10 @@ static void ion_handle_kmap_put(struct ion_handle *handle)
>  {
>         struct ion_buffer *buffer = handle->buffer;
>
> +       if (!handle->kmap_cnt) {
> +               WARN(1, "%s: Double unmap detected! bailing...\n", __func__);
> +               return;
> +       }
>         handle->kmap_cnt--;
>         if (!handle->kmap_cnt)
>                 ion_buffer_kmap_put(buffer);
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
>
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.

Acked-by: Colin Cross <ccross@android.com>

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Re: [PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around

[Mitchel Humpherys]

++greg-kh and devel@driverdev.osuosl.org
(my bad for missing you the first time around)

On Thu, May 22 2014 at 06:09:11 PM, Colin Cross <ccross@android.com> wrote:
> On Thu, May 22, 2014 at 5:51 PM, Mitchel Humpherys
> <mitchelh@codeaurora.org> wrote:
>> There are certain client bugs (double unmap, for example) that can cause
>> the handle->kmap_cnt (an unsigned int) to wrap around from zero. This
>> causes problems when the handle is destroyed because we have:
>>
>>         while (handle->kmap_cnt)
>>                 ion_handle_kmap_put(handle);
>>
>> which takes a long time to complete when kmap_cnt starts at ~0 and can
>> result in a watchdog timeout.
>>
>> WARN and bail when kmap_cnt is about to wrap around from zero.
>>
>> Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
>> ---
>>  drivers/staging/android/ion/ion.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
>> index 3d5bf14722..f55f61a4cc 100644
>> --- a/drivers/staging/android/ion/ion.c
>> +++ b/drivers/staging/android/ion/ion.c
>> @@ -626,6 +626,10 @@ static void ion_handle_kmap_put(struct ion_handle *handle)
>>  {
>>         struct ion_buffer *buffer = handle->buffer;
>>
>> +       if (!handle->kmap_cnt) {
>> +               WARN(1, "%s: Double unmap detected! bailing...\n", __func__);
>> +               return;
>> +       }
>>         handle->kmap_cnt--;
>>         if (!handle->kmap_cnt)
>>                 ion_buffer_kmap_put(buffer);
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>> hosted by The Linux Foundation
>>
>> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>
> Acked-by: Colin Cross <ccross@android.com>

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Re: [PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around

[Greg Kroah-Hartman]

On Fri, May 23, 2014 at 11:34:59AM -0700, Mitchel Humpherys wrote:
> ++greg-kh and devel@driverdev.osuosl.org
> (my bad for missing you the first time around)

What can I do with this?  Please send patches to me in a format that I
can actually apply them in...

thanks,

greg k-h

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