2015-06-29 21:18:57

by Benoit Parrot

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

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: <[email protected]> # v4.0+
Signed-off-by: Benoit Parrot <[email protected]>
---
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

2015-07-07 11:13:10

by Lad, Prabhakar

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

On Mon, Jun 29, 2015 at 10:18 PM, Benoit Parrot <[email protected]> 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: <[email protected]> # v4.0+
> Signed-off-by: Benoit Parrot <[email protected]>

Acked-by: Lad, Prabhakar <[email protected]>

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
>

2015-07-13 09:22:38

by Hans Verkuil

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

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: <[email protected]> # v4.0+
> Signed-off-by: Benoit Parrot <[email protected]>
> ---
> 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;
>