[PATCH RESEND] fpga: region: Fix possible memory leak in fpga_region_register_full()

[PATCH RESEND] fpga: region: Fix possible memory leak in fpga_region_register_full()

[Jinjie Ruan]

If device_register() fails in fpga_region_register_full(), the region
allocated by kzalloc() and the id allocated by ida_alloc() also need be
freed otherwise will cause memory leak.

Fixes: 8886a579744f ("fpga: region: Use standard dev_release for class driver")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 drivers/fpga/fpga-region.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
index b364a929425c..9dc6314976ef 100644
--- a/drivers/fpga/fpga-region.c
+++ b/drivers/fpga/fpga-region.c
@@ -228,12 +228,13 @@ fpga_region_register_full(struct device *parent, const struct fpga_region_info *
 
 	ret = device_register(&region->dev);
 	if (ret) {
-		put_device(&region->dev);
-		return ERR_PTR(ret);
+		goto err_put_device;
 	}
 
 	return region;
 
+err_put_device:
+	put_device(&region->dev);
 err_remove:
 	ida_free(&fpga_region_ida, id);
 err_free:
-- 
2.34.1

Re: [PATCH RESEND] fpga: region: Fix possible memory leak in fpga_region_register_full()

[Xu Yilun]

On Thu, Sep 28, 2023 at 05:16:36PM +0800, Jinjie Ruan wrote:
> If device_register() fails in fpga_region_register_full(), the region
> allocated by kzalloc() and the id allocated by ida_alloc() also need be
> freed otherwise will cause memory leak.

How did you observe the memory leak? Please help provide some trace.

Thanks,
Yilun

> 
> Fixes: 8886a579744f ("fpga: region: Use standard dev_release for class driver")
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>  drivers/fpga/fpga-region.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
> index b364a929425c..9dc6314976ef 100644
> --- a/drivers/fpga/fpga-region.c
> +++ b/drivers/fpga/fpga-region.c
> @@ -228,12 +228,13 @@ fpga_region_register_full(struct device *parent, const struct fpga_region_info *
>  
>  	ret = device_register(&region->dev);
>  	if (ret) {
> -		put_device(&region->dev);
> -		return ERR_PTR(ret);
> +		goto err_put_device;
>  	}
>  
>  	return region;
>  
> +err_put_device:
> +	put_device(&region->dev);
>  err_remove:
>  	ida_free(&fpga_region_ida, id);
>  err_free:
> -- 
> 2.34.1
> 

Re: [PATCH RESEND] fpga: region: Fix possible memory leak in fpga_region_register_full()

[Russ Weight]

On 9/28/23 02:16, Jinjie Ruan wrote:
> If device_register() fails in fpga_region_register_full(), the region
> allocated by kzalloc() and the id allocated by ida_alloc() also need be
> freed otherwise will cause memory leak.
>
> Fixes: 8886a579744f ("fpga: region: Use standard dev_release for class driver")
> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
> ---
>  drivers/fpga/fpga-region.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
> index b364a929425c..9dc6314976ef 100644
> --- a/drivers/fpga/fpga-region.c
> +++ b/drivers/fpga/fpga-region.c
> @@ -228,12 +228,13 @@ fpga_region_register_full(struct device *parent, const struct fpga_region_info *
>  
>  	ret = device_register(&region->dev);

The comments for device_register() say:

 * NOTE: _Never_ directly free @dev after calling this function, even
 * if it returned an error! Always use put_device() to give up the
 * reference initialized in this function instead.

Note that dev is embedded in the region structure, so freeing region
means freeing dev.

The expectation is that after device_register() has been called, even
if it returns an error, put_device() is used to lower the reference
count. When the reference count is zero, the fpga_region_dev_release()
function is called. fpga_region_dev_release() frees calls ida_free()
and frees the region.

Have you observed different behavior? Do you have evidence of a memory
leak?

Thanks,
- Russ

>  	if (ret) {
> -		put_device(&region->dev);
> -		return ERR_PTR(ret);
> +		goto err_put_device;
>  	}
>  
>  	return region;
>  
> +err_put_device:
> +	put_device(&region->dev);
>  err_remove:
>  	ida_free(&fpga_region_ida, id);
>  err_free:

Re: [PATCH RESEND] fpga: region: Fix possible memory leak in fpga_region_register_full()

[Ruan Jinjie]

On 2023/9/28 23:45, Russ Weight wrote:
> 
> 
> On 9/28/23 02:16, Jinjie Ruan wrote:
>> If device_register() fails in fpga_region_register_full(), the region
>> allocated by kzalloc() and the id allocated by ida_alloc() also need be
>> freed otherwise will cause memory leak.
>>
>> Fixes: 8886a579744f ("fpga: region: Use standard dev_release for class driver")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
>> ---
>>  drivers/fpga/fpga-region.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
>> index b364a929425c..9dc6314976ef 100644
>> --- a/drivers/fpga/fpga-region.c
>> +++ b/drivers/fpga/fpga-region.c
>> @@ -228,12 +228,13 @@ fpga_region_register_full(struct device *parent, const struct fpga_region_info *
>>  
>>  	ret = device_register(&region->dev);
> 
> The comments for device_register() say:
> 
>  * NOTE: _Never_ directly free @dev after calling this function, even
>  * if it returned an error! Always use put_device() to give up the
>  * reference initialized in this function instead.
> 
> Note that dev is embedded in the region structure, so freeing region
> means freeing dev.
> 
> The expectation is that after device_register() has been called, even
> if it returns an error, put_device() is used to lower the reference
> count. When the reference count is zero, the fpga_region_dev_release()
> function is called. fpga_region_dev_release() frees calls ida_free()
> and frees the region.

Right!

> 
> Have you observed different behavior? Do you have evidence of a memory
> leak?

I have noticed a memory leak in using fpga_region_register_full() in
fpga-region-test.c. I'll send the patch sooner.

> 
> Thanks,
> - Russ
> 
>>  	if (ret) {
>> -		put_device(&region->dev);
>> -		return ERR_PTR(ret);
>> +		goto err_put_device;
>>  	}
>>  
>>  	return region;
>>  
>> +err_put_device:
>> +	put_device(&region->dev);
>>  err_remove:
>>  	ida_free(&fpga_region_ida, id);
>>  err_free:
>