2023-09-28 09:41:30

by Jinjie Ruan

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

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 <[email protected]>
---
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

2023-09-28 17:59:32

by Russ Weight

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

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 <[email protected]>
> ---
> 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:

2023-09-29 00:09:33

by Xu Yilun

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

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 <[email protected]>
> ---
> 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
>

2023-10-07 09:15:23

by Jinjie Ruan

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

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 <[email protected]>
>> ---
>> 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:
>