[Patch v3 1/1] media: am437x-vpfe: Fix a race condition during release

[Patch v3 1/1] media: am437x-vpfe: Fix a race condition during release

[Benoit Parrot]

There was a race condition where during cleanup/release operation
on-going streaming would cause a kernel panic because the hardware
module was disabled prematurely with IRQ still pending.

Fixes: 417d2e507edc ("[media] media: platform: add VPFE capture driver support for AM437X")
Cc: <stable@vger.kernel.org> # v4.0+
Signed-off-by: Benoit Parrot <bparrot@ti.com>
---
Changes since v2:
- fix the stable commit reference syntax

 drivers/media/platform/am437x/am437x-vpfe.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/am437x/am437x-vpfe.c b/drivers/media/platform/am437x/am437x-vpfe.c
index a30cc2f7e4f1..eb25c43da126 100644
--- a/drivers/media/platform/am437x/am437x-vpfe.c
+++ b/drivers/media/platform/am437x/am437x-vpfe.c
@@ -1185,14 +1185,21 @@ static int vpfe_initialize_device(struct vpfe_device *vpfe)
 static int vpfe_release(struct file *file)
 {
 	struct vpfe_device *vpfe = video_drvdata(file);
+	bool fh_singular = v4l2_fh_is_singular_file(file);
 	int ret;
 
 	mutex_lock(&vpfe->lock);
 
-	if (v4l2_fh_is_singular_file(file))
-		vpfe_ccdc_close(&vpfe->ccdc, vpfe->pdev);
+	/* the release helper will cleanup any on-going streaming */
 	ret = _vb2_fop_release(file, NULL);
 
+	/*
+	 * If this was the last open file.
+	 * Then de-initialize hw module.
+	 */
+	if (fh_singular)
+		vpfe_ccdc_close(&vpfe->ccdc, vpfe->pdev);
+
 	mutex_unlock(&vpfe->lock);
 
 	return ret;
-- 
1.8.5.1

Re: [Patch v3 1/1] media: am437x-vpfe: Fix a race condition during release

[Lad, Prabhakar]

On Mon, Jun 29, 2015 at 10:18 PM, Benoit Parrot <bparrot@ti.com> wrote:
> There was a race condition where during cleanup/release operation
> on-going streaming would cause a kernel panic because the hardware
> module was disabled prematurely with IRQ still pending.
>
> Fixes: 417d2e507edc ("[media] media: platform: add VPFE capture driver support for AM437X")
> Cc: <stable@vger.kernel.org> # v4.0+
> Signed-off-by: Benoit Parrot <bparrot@ti.com>

Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>

Cheers,
--Prabhakar Lad

> ---
> Changes since v2:
> - fix the stable commit reference syntax
>
>  drivers/media/platform/am437x/am437x-vpfe.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/am437x/am437x-vpfe.c b/drivers/media/platform/am437x/am437x-vpfe.c
> index a30cc2f7e4f1..eb25c43da126 100644
> --- a/drivers/media/platform/am437x/am437x-vpfe.c
> +++ b/drivers/media/platform/am437x/am437x-vpfe.c
> @@ -1185,14 +1185,21 @@ static int vpfe_initialize_device(struct vpfe_device *vpfe)
>  static int vpfe_release(struct file *file)
>  {
>         struct vpfe_device *vpfe = video_drvdata(file);
> +       bool fh_singular = v4l2_fh_is_singular_file(file);
>         int ret;
>
>         mutex_lock(&vpfe->lock);
>
> -       if (v4l2_fh_is_singular_file(file))
> -               vpfe_ccdc_close(&vpfe->ccdc, vpfe->pdev);
> +       /* the release helper will cleanup any on-going streaming */
>         ret = _vb2_fop_release(file, NULL);
>
> +       /*
> +        * If this was the last open file.
> +        * Then de-initialize hw module.
> +        */
> +       if (fh_singular)
> +               vpfe_ccdc_close(&vpfe->ccdc, vpfe->pdev);
> +
>         mutex_unlock(&vpfe->lock);
>
>         return ret;
> --
> 1.8.5.1
>

Re: [Patch v3 1/1] media: am437x-vpfe: Fix a race condition during release

[Hans Verkuil]

On 06/29/2015 11:18 PM, Benoit Parrot wrote:
> There was a race condition where during cleanup/release operation
> on-going streaming would cause a kernel panic because the hardware
> module was disabled prematurely with IRQ still pending.
> 
> Fixes: 417d2e507edc ("[media] media: platform: add VPFE capture driver support for AM437X")
> Cc: <stable@vger.kernel.org> # v4.0+
> Signed-off-by: Benoit Parrot <bparrot@ti.com>
> ---
> Changes since v2:
> - fix the stable commit reference syntax
> 
>  drivers/media/platform/am437x/am437x-vpfe.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/am437x/am437x-vpfe.c b/drivers/media/platform/am437x/am437x-vpfe.c
> index a30cc2f7e4f1..eb25c43da126 100644
> --- a/drivers/media/platform/am437x/am437x-vpfe.c
> +++ b/drivers/media/platform/am437x/am437x-vpfe.c
> @@ -1185,14 +1185,21 @@ static int vpfe_initialize_device(struct vpfe_device *vpfe)
>  static int vpfe_release(struct file *file)
>  {
>  	struct vpfe_device *vpfe = video_drvdata(file);
> +	bool fh_singular = v4l2_fh_is_singular_file(file);

Close, but no cigar.

The assignment to fh_singular should be moved inside the mutex. Right now
there still is a race condition between setting fh_singular and taking
the lock.

Regards,

	Hans

>  	int ret;
>  
>  	mutex_lock(&vpfe->lock);
>  
> -	if (v4l2_fh_is_singular_file(file))
> -		vpfe_ccdc_close(&vpfe->ccdc, vpfe->pdev);
> +	/* the release helper will cleanup any on-going streaming */
>  	ret = _vb2_fop_release(file, NULL);
>  
> +	/*
> +	 * If this was the last open file.
> +	 * Then de-initialize hw module.
> +	 */
> +	if (fh_singular)
> +		vpfe_ccdc_close(&vpfe->ccdc, vpfe->pdev);
> +
>  	mutex_unlock(&vpfe->lock);
>  
>  	return ret;
>