[RESEND 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 
Acked-by: Colin Cross 
---
Resending since I missed a few folks on the original. Also retaining
Colin's Acked-by.
---
 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

[Greg Kroah-Hartman]

On Fri, May 23, 2014 at 11:34:59AM -0700, Mitchel Humpherys wrote:
> ++greg-kh and de...@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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Re: [PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around

[Mitchel Humpherys]

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

On Thu, May 22 2014 at 06:09:11 PM, Colin Cross  wrote:
> On Thu, May 22, 2014 at 5:51 PM, Mitchel Humpherys
>  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 
>> ---
>>  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+unsubscr...@android.com.
>
> Acked-by: Colin Cross 

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