[v1] devres: Fix devm_krealloc() allocating memory with wrong size

[PATCH v1] devres: Fix devm_krealloc() allocating memory with wrong size

Posted by Zijun Hu 1 year, 6 months ago

Kernel API devm_krealloc() calls alloc_dr() with wrong argument
@total_new_size, and it will cause more memory to be allocated
than required, fixed by using @new_size as alloc_dr()'s argument.

Fixes: f82485722e5d ("devres: provide devm_krealloc()")
Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
---
 drivers/base/devres.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 3df0025d12aa..1cf87ddf1f55 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -898,7 +898,7 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
 	 * taking the lock as most probably the caller uses GFP_KERNEL.
 	 */
 	new_dr = alloc_dr(devm_kmalloc_release,
-			  total_new_size, gfp, dev_to_node(dev));
+			  new_size, gfp, dev_to_node(dev));
 	if (!new_dr)
 		return NULL;
 
-- 
2.7.4

Re: [PATCH v1] devres: Fix devm_krealloc() allocating memory with wrong size

Posted by Greg KH 1 year, 6 months ago

On Sun, Jun 16, 2024 at 05:54:15PM +0800, Zijun Hu wrote:
> Kernel API devm_krealloc() calls alloc_dr() with wrong argument
> @total_new_size, and it will cause more memory to be allocated
> than required, fixed by using @new_size as alloc_dr()'s argument.
> 
> Fixes: f82485722e5d ("devres: provide devm_krealloc()")
> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
> ---
>  drivers/base/devres.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index 3df0025d12aa..1cf87ddf1f55 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -898,7 +898,7 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
>  	 * taking the lock as most probably the caller uses GFP_KERNEL.
>  	 */
>  	new_dr = alloc_dr(devm_kmalloc_release,
> -			  total_new_size, gfp, dev_to_node(dev));
> +			  new_size, gfp, dev_to_node(dev));

Wait, are you sure?  Did you properly test this?  What is the actual
savings and how do you handle the fact that you are now not allocating
the space reserved for the devres structure itself?

thanks,

greg k-h

Re: [PATCH v1] devres: Fix devm_krealloc() allocating memory with wrong size

Posted by quic_zijuhu 1 year, 6 months ago

On 6/16/2024 6:02 PM, Greg KH wrote:
> On Sun, Jun 16, 2024 at 05:54:15PM +0800, Zijun Hu wrote:
>> Kernel API devm_krealloc() calls alloc_dr() with wrong argument
>> @total_new_size, and it will cause more memory to be allocated
>> than required, fixed by using @new_size as alloc_dr()'s argument.
>>
>> Fixes: f82485722e5d ("devres: provide devm_krealloc()")
>> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
>> ---
>>  drivers/base/devres.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
>> index 3df0025d12aa..1cf87ddf1f55 100644
>> --- a/drivers/base/devres.c
>> +++ b/drivers/base/devres.c
>> @@ -898,7 +898,7 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
>>  	 * taking the lock as most probably the caller uses GFP_KERNEL.
>>  	 */
>>  	new_dr = alloc_dr(devm_kmalloc_release,
>> -			  total_new_size, gfp, dev_to_node(dev));
>> +			  new_size, gfp, dev_to_node(dev));
> 
> Wait, are you sure?  Did you properly test this?  What is the actual
> savings and how do you handle the fact that you are now not allocating
> the space reserved for the devres structure itself?
> 
sure even if i did not test it.
beware that alloc_dr() will call check_dr_size() to reserve space for
devres structure.

it will reserve the devres structure two times if using wrong
@total_new_size. it is obvious wrong.

> thanks,
> 
> greg k-h

Re: [PATCH v1] devres: Fix devm_krealloc() allocating memory with wrong size

Posted by Greg KH 1 year, 6 months ago

On Sun, Jun 16, 2024 at 06:10:02PM +0800, quic_zijuhu wrote:
> On 6/16/2024 6:02 PM, Greg KH wrote:
> > On Sun, Jun 16, 2024 at 05:54:15PM +0800, Zijun Hu wrote:
> >> Kernel API devm_krealloc() calls alloc_dr() with wrong argument
> >> @total_new_size, and it will cause more memory to be allocated
> >> than required, fixed by using @new_size as alloc_dr()'s argument.
> >>
> >> Fixes: f82485722e5d ("devres: provide devm_krealloc()")
> >> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
> >> ---
> >>  drivers/base/devres.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> >> index 3df0025d12aa..1cf87ddf1f55 100644
> >> --- a/drivers/base/devres.c
> >> +++ b/drivers/base/devres.c
> >> @@ -898,7 +898,7 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
> >>  	 * taking the lock as most probably the caller uses GFP_KERNEL.
> >>  	 */
> >>  	new_dr = alloc_dr(devm_kmalloc_release,
> >> -			  total_new_size, gfp, dev_to_node(dev));
> >> +			  new_size, gfp, dev_to_node(dev));
> > 
> > Wait, are you sure?  Did you properly test this?  What is the actual
> > savings and how do you handle the fact that you are now not allocating
> > the space reserved for the devres structure itself?
> > 
> sure even if i did not test it.
> beware that alloc_dr() will call check_dr_size() to reserve space for
> devres structure.
> 
> it will reserve the devres structure two times if using wrong
> @total_new_size. it is obvious wrong.

Ah, I missed that, that is tricky.  Please document this better when you
resubmit a new version.

And of course, please test it.

thanks,

greg k-h

Re: [PATCH v1] devres: Fix devm_krealloc() allocating memory with wrong size

Posted by quic_zijuhu 1 year, 6 months ago

On 6/16/2024 6:17 PM, Greg KH wrote:
> On Sun, Jun 16, 2024 at 06:10:02PM +0800, quic_zijuhu wrote:
>> On 6/16/2024 6:02 PM, Greg KH wrote:
>>> On Sun, Jun 16, 2024 at 05:54:15PM +0800, Zijun Hu wrote:
>>>> Kernel API devm_krealloc() calls alloc_dr() with wrong argument
>>>> @total_new_size, and it will cause more memory to be allocated
>>>> than required, fixed by using @new_size as alloc_dr()'s argument.
>>>>
>>>> Fixes: f82485722e5d ("devres: provide devm_krealloc()")
>>>> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
>>>> ---
>>>>  drivers/base/devres.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
>>>> index 3df0025d12aa..1cf87ddf1f55 100644
>>>> --- a/drivers/base/devres.c
>>>> +++ b/drivers/base/devres.c
>>>> @@ -898,7 +898,7 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
>>>>  	 * taking the lock as most probably the caller uses GFP_KERNEL.
>>>>  	 */
>>>>  	new_dr = alloc_dr(devm_kmalloc_release,
>>>> -			  total_new_size, gfp, dev_to_node(dev));
>>>> +			  new_size, gfp, dev_to_node(dev));
>>>
>>> Wait, are you sure?  Did you properly test this?  What is the actual
>>> savings and how do you handle the fact that you are now not allocating
>>> the space reserved for the devres structure itself?
>>>
>> sure even if i did not test it.
>> beware that alloc_dr() will call check_dr_size() to reserve space for
>> devres structure.
>>
>> it will reserve the devres structure two times if using wrong
>> @total_new_size. it is obvious wrong.
> 
> Ah, I missed that, that is tricky.  Please document this better when you
> resubmit a new version.
> 
okay. will send v2.
> And of course, please test it.
okay.
> 
> thanks,
> 
> greg k-h

Re: [PATCH v1] devres: Fix devm_krealloc() allocating memory with wrong size

Posted by Greg KH 1 year, 6 months ago

On Sun, Jun 16, 2024 at 05:54:15PM +0800, Zijun Hu wrote:
> Kernel API devm_krealloc() calls alloc_dr() with wrong argument
> @total_new_size, and it will cause more memory to be allocated
> than required, fixed by using @new_size as alloc_dr()'s argument.
> 
> Fixes: f82485722e5d ("devres: provide devm_krealloc()")
> Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
> ---
>  drivers/base/devres.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
> index 3df0025d12aa..1cf87ddf1f55 100644
> --- a/drivers/base/devres.c
> +++ b/drivers/base/devres.c
> @@ -898,7 +898,7 @@ void *devm_krealloc(struct device *dev, void *ptr, size_t new_size, gfp_t gfp)
>  	 * taking the lock as most probably the caller uses GFP_KERNEL.
>  	 */
>  	new_dr = alloc_dr(devm_kmalloc_release,
> -			  total_new_size, gfp, dev_to_node(dev));
> +			  new_size, gfp, dev_to_node(dev));
>  	if (!new_dr)
>  		return NULL;
>  
> -- 
> 2.7.4
> 

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