Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
2012/12/3 Dan Carpenter :
> On Mon, Dec 03, 2012 at 09:09:59AM +0900, JoonSoo Kim wrote:
>> Hello, Dan.
>>
>> 2012/12/2 Dan Carpenter :
>> > On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
>> >> @@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area
>> >> *asma, unsigned long cmd,
>> >> pgstart = pin.offset / PAGE_SIZE;
>> >> pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
>> >>
>> >> - mutex_lock(_mutex);
>> >> + if (asma->shared_mapping) {
>> >> + mutex_lock(_mutex);
>> >
>> > Wouldn't we need to hold the mutex while we check the
>> > ->shared_mapping?
>>
>> I doesn't fully understand ashmem's lock semantic.
>> Code for retrieving some value of asma instance doesn't hold the mutex, now.
>> For example, in ashmem_ioctl(), asma->size, asma->prot_mask.
>> And in ashmem_pin_unpin(), there is asma->file, asma->size which is
>> retrieved without the mutex.
>> According to this semantic, the mutex doesn't need for checking
>> asma->shared_mapping.
>
> The ashmem_ioctl() is clearly racy. :P asma->size can be modified
> and read at the same time. It's not an example to follow.
Okay :)
I will insert a code for holding the mutex in next spin.
Thanks!
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Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
2012/12/3 Dan Carpenter dan.carpen...@oracle.com:
On Mon, Dec 03, 2012 at 09:09:59AM +0900, JoonSoo Kim wrote:
Hello, Dan.
2012/12/2 Dan Carpenter dan.carpen...@oracle.com:
On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
@@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area
*asma, unsigned long cmd,
pgstart = pin.offset / PAGE_SIZE;
pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
- mutex_lock(ashmem_mutex);
+ if (asma-shared_mapping) {
+ mutex_lock(ashmem_mutex);
Wouldn't we need to hold the mutex while we check the
-shared_mapping?
I doesn't fully understand ashmem's lock semantic.
Code for retrieving some value of asma instance doesn't hold the mutex, now.
For example, in ashmem_ioctl(), asma-size, asma-prot_mask.
And in ashmem_pin_unpin(), there is asma-file, asma-size which is
retrieved without the mutex.
According to this semantic, the mutex doesn't need for checking
asma-shared_mapping.
The ashmem_ioctl() is clearly racy. :P asma-size can be modified
and read at the same time. It's not an example to follow.
Okay :)
I will insert a code for holding the mutex in next spin.
Thanks!
--
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the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
On Mon, Dec 03, 2012 at 09:09:59AM +0900, JoonSoo Kim wrote:
> Hello, Dan.
>
> 2012/12/2 Dan Carpenter :
> > On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
> >> @@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area
> >> *asma, unsigned long cmd,
> >> pgstart = pin.offset / PAGE_SIZE;
> >> pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
> >>
> >> - mutex_lock(_mutex);
> >> + if (asma->shared_mapping) {
> >> + mutex_lock(_mutex);
> >
> > Wouldn't we need to hold the mutex while we check the
> > ->shared_mapping?
>
> I doesn't fully understand ashmem's lock semantic.
> Code for retrieving some value of asma instance doesn't hold the mutex, now.
> For example, in ashmem_ioctl(), asma->size, asma->prot_mask.
> And in ashmem_pin_unpin(), there is asma->file, asma->size which is
> retrieved without the mutex.
> According to this semantic, the mutex doesn't need for checking
> asma->shared_mapping.
The ashmem_ioctl() is clearly racy. :P asma->size can be modified
and read at the same time. It's not an example to follow.
regards,
dan carpenter
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Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
Hello, Dan.
2012/12/2 Dan Carpenter :
> On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
>> @@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area *asma,
>> unsigned long cmd,
>> pgstart = pin.offset / PAGE_SIZE;
>> pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
>>
>> - mutex_lock(_mutex);
>> + if (asma->shared_mapping) {
>> + mutex_lock(_mutex);
>
> Wouldn't we need to hold the mutex while we check the
> ->shared_mapping?
I doesn't fully understand ashmem's lock semantic.
Code for retrieving some value of asma instance doesn't hold the mutex, now.
For example, in ashmem_ioctl(), asma->size, asma->prot_mask.
And in ashmem_pin_unpin(), there is asma->file, asma->size which is
retrieved without the mutex.
According to this semantic, the mutex doesn't need for checking
asma->shared_mapping.
Thanks for review!
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
Hello, Dan.
2012/12/2 Dan Carpenter dan.carpen...@oracle.com:
On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
@@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area *asma,
unsigned long cmd,
pgstart = pin.offset / PAGE_SIZE;
pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
- mutex_lock(ashmem_mutex);
+ if (asma-shared_mapping) {
+ mutex_lock(ashmem_mutex);
Wouldn't we need to hold the mutex while we check the
-shared_mapping?
I doesn't fully understand ashmem's lock semantic.
Code for retrieving some value of asma instance doesn't hold the mutex, now.
For example, in ashmem_ioctl(), asma-size, asma-prot_mask.
And in ashmem_pin_unpin(), there is asma-file, asma-size which is
retrieved without the mutex.
According to this semantic, the mutex doesn't need for checking
asma-shared_mapping.
Thanks for review!
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
On Mon, Dec 03, 2012 at 09:09:59AM +0900, JoonSoo Kim wrote:
Hello, Dan.
2012/12/2 Dan Carpenter dan.carpen...@oracle.com:
On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
@@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area
*asma, unsigned long cmd,
pgstart = pin.offset / PAGE_SIZE;
pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
- mutex_lock(ashmem_mutex);
+ if (asma-shared_mapping) {
+ mutex_lock(ashmem_mutex);
Wouldn't we need to hold the mutex while we check the
-shared_mapping?
I doesn't fully understand ashmem's lock semantic.
Code for retrieving some value of asma instance doesn't hold the mutex, now.
For example, in ashmem_ioctl(), asma-size, asma-prot_mask.
And in ashmem_pin_unpin(), there is asma-file, asma-size which is
retrieved without the mutex.
According to this semantic, the mutex doesn't need for checking
asma-shared_mapping.
The ashmem_ioctl() is clearly racy. :P asma-size can be modified
and read at the same time. It's not an example to follow.
regards,
dan carpenter
--
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the body of a message to majord...@vger.kernel.org
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Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
> @@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area *asma,
> unsigned long cmd,
> pgstart = pin.offset / PAGE_SIZE;
> pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
>
> - mutex_lock(_mutex);
> + if (asma->shared_mapping) {
> + mutex_lock(_mutex);
Wouldn't we need to hold the mutex while we check the
->shared_mapping?
regards,
dan carpenter
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC PATCH] staging, android, ashmem: invalidate pin/unpin ioctl for private map
On Sat, Dec 01, 2012 at 02:45:57AM +0900, Joonsoo Kim wrote:
@@ -614,21 +616,35 @@ static int ashmem_pin_unpin(struct ashmem_area *asma,
unsigned long cmd,
pgstart = pin.offset / PAGE_SIZE;
pgend = pgstart + (pin.len / PAGE_SIZE) - 1;
- mutex_lock(ashmem_mutex);
+ if (asma-shared_mapping) {
+ mutex_lock(ashmem_mutex);
Wouldn't we need to hold the mutex while we check the
-shared_mapping?
regards,
dan carpenter
--
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the body of a message to majord...@vger.kernel.org
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