[PATCH -next] spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()

[PATCH -next] spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()

[weiyj_lk at 163.com]

From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>

Once a spi_master_get() call succeeds, we need an additional
spi_master_put() call to free the memory, otherwise we will
leak a reference to master. Fix by removing the unnecessary
spi_master_get() call.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
---
 drivers/spi/spi-s3c64xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index df88fa1..001c9eb 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -1211,7 +1211,7 @@ err0:
 
 static int s3c64xx_spi_remove(struct platform_device *pdev)
 {
-	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
+	struct spi_master *master = platform_get_drvdata(pdev);
 	struct s3c64xx_spi_driver_data *sdd = spi_master_get_devdata(master);
 
 	pm_runtime_get_sync(&pdev->dev);

[PATCH -next] spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()

[Andi Shyti]

Hi Wei,

> Once a spi_master_get() call succeeds, we need an additional
> spi_master_put() call to free the memory, otherwise we will
> leak a reference to master. Fix by removing the unnecessary
> spi_master_get() call.
> 
> Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>

The patch doesn't have anything wrong, but what you write in the
description is not what you are doing in the patch.

There is no memory allocated in spi_master_get and nothing leaks.
Besides master's resources are managed, so that there would
not be any need to call spi_master_put().

spi_master_put() has been, indeed, removed in this commit:
91800f0e90050a4db4c77e940796f501e02af8be.

But even if you correct the commit log, I don't see much
advantage for this patch on its own.

Thanks,
Andi

> ---
>  drivers/spi/spi-s3c64xx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> index df88fa1..001c9eb 100644
> --- a/drivers/spi/spi-s3c64xx.c
> +++ b/drivers/spi/spi-s3c64xx.c
> @@ -1211,7 +1211,7 @@ err0:
>  
>  static int s3c64xx_spi_remove(struct platform_device *pdev)
>  {
> -	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
> +	struct spi_master *master = platform_get_drvdata(pdev);
>  	struct s3c64xx_spi_driver_data *sdd = spi_master_get_devdata(master);
>  
>  	pm_runtime_get_sync(&pdev->dev);
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

[PATCH -next] spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()

[weiyj]

Hi Andi,

At 2016-07-13 12:50:30, "Andi Shyti" <andi.shyti@samsung.com> wrote:
>Hi Wei,
>
>> Once a spi_master_get() call succeeds, we need an additional
>> spi_master_put() call to free the memory, otherwise we will
>> leak a reference to master. Fix by removing the unnecessary
>> spi_master_get() call.
>> 
>> Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
>
>The patch doesn't have anything wrong, but what you write in the
>description is not what you are doing in the patch.
>
>There is no memory allocated in spi_master_get and nothing leaks.
>Besides master's resources are managed, so that there would
>not be any need to call spi_master_put().
>
>spi_master_put() has been, indeed, removed in this commit:
>91800f0e90050a4db4c77e940796f501e02af8be.
>

master allocated in spi_alloc_master() need device reference count to zero
to be freed.

The call sequence spi_alloc_master/spi_register_master/spi_unregister_master
is complete; it reduces the device reference count to zero, which results in
device memory being freed.

In commit 91800f0e90050a4db4c77e940796f501e02af8be, 
devm_spi_register_master() equal to spi_register_master() and auto call
spi_unregister_master() when remove. But  remove spi_master_put()
will cause the device reference count left no zero, since spi_master_get()
is callled at the begin of remove function already.

So I think we should either remove the spi_master_get() or add spi_master_put()
before return from remove function.

Regards,
Yongjun Wei

[PATCH -next] spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()

[Andi Shyti]

Hi Wei,

> >> Once a spi_master_get() call succeeds, we need an additional
> >> spi_master_put() call to free the memory, otherwise we will
> >> leak a reference to master. Fix by removing the unnecessary
> >> spi_master_get() call.
> >> 
> >> Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
> >
> >The patch doesn't have anything wrong, but what you write in the
> >description is not what you are doing in the patch.
> >
> >There is no memory allocated in spi_master_get and nothing leaks.
> >Besides master's resources are managed, so that there would
> >not be any need to call spi_master_put().
> >
> >spi_master_put() has been, indeed, removed in this commit:
> >91800f0e90050a4db4c77e940796f501e02af8be.
> >
> 
> master allocated in spi_alloc_master() need device reference count to zero
> to be freed.
> 
> The call sequence spi_alloc_master/spi_register_master/spi_unregister_master
> is complete; it reduces the device reference count to zero, which results in
> device memory being freed.
> 
> In commit 91800f0e90050a4db4c77e940796f501e02af8be, 
> devm_spi_register_master() equal to spi_register_master() and auto call
> spi_unregister_master() when remove. But  remove spi_master_put()
> will cause the device reference count left no zero, since spi_master_get()
> is callled at the begin of remove function already.
> 
> So I think we should either remove the spi_master_get() or add spi_master_put()
> before return from remove function.

Yes, you are right, I missed this part :)

Thanks,
Andi

[PATCH -next] spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()

[Andi Shyti]

On Tue, Jul 12, 2016 at 11:08:42AM +0000, weiyj_lk at 163.com wrote:
> From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
> 
> Once a spi_master_get() call succeeds, we need an additional
> spi_master_put() call to free the memory, otherwise we will
> leak a reference to master. Fix by removing the unnecessary
> spi_master_get() call.
> 
> Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>

After our discussion, I checked it again and feel free to add

Reviewed-by: Andi Shyti <andi.shyti@samsung.com>

Thanks,
Andi

> ---
>  drivers/spi/spi-s3c64xx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> index df88fa1..001c9eb 100644
> --- a/drivers/spi/spi-s3c64xx.c
> +++ b/drivers/spi/spi-s3c64xx.c
> @@ -1211,7 +1211,7 @@ err0:
>  
>  static int s3c64xx_spi_remove(struct platform_device *pdev)
>  {
> -	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
> +	struct spi_master *master = platform_get_drvdata(pdev);
>  	struct s3c64xx_spi_driver_data *sdd = spi_master_get_devdata(master);
>  
>  	pm_runtime_get_sync(&pdev->dev);
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in
> the body of a message to majordomo at vger.kernel.org
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> 

Applied "spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()" to the spi tree

[Mark Brown]

The patch

   spi: s3c64xx: fix reference leak to master in s3c64xx_spi_remove()

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From 9f135787b1d29b0069059b580c1c77965e5e8af4 Mon Sep 17 00:00:00 2001
From: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Date: Tue, 12 Jul 2016 11:08:42 +0000
Subject: [PATCH] spi: s3c64xx: fix reference leak to master in
 s3c64xx_spi_remove()

Once a spi_master_get() call succeeds, we need an additional
spi_master_put() call to free the memory, otherwise we will
leak a reference to master. Fix by removing the unnecessary
spi_master_get() call.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Reviewed-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/spi/spi-s3c64xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index df88fa161d8a..001c9ebf884d 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -1211,7 +1211,7 @@ err0:
 
 static int s3c64xx_spi_remove(struct platform_device *pdev)
 {
-	struct spi_master *master = spi_master_get(platform_get_drvdata(pdev));
+	struct spi_master *master = platform_get_drvdata(pdev);
 	struct s3c64xx_spi_driver_data *sdd = spi_master_get_devdata(master);
 
 	pm_runtime_get_sync(&pdev->dev);
-- 
2.8.1