2022-08-18 20:49:43

by Nicolas Dufresne

Subject: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()

From: Dmitry Osipenko <[email protected]>

The busy status bit may never de-assert if number of programmed skip
bits is incorrect, resulting in a kernel hang because the bit is polled
endlessly in the code. Fix it by adding timeout for the bit-polling.
This problem is reproducible by setting the data_bit_offset field of
the HEVC slice params to a wrong value by userspace.

Cc: [email protected]
Reported-by: Nicolas Dufresne <[email protected]>
Signed-off-by: Dmitry Osipenko <[email protected]>
Signed-off-by: Nicolas Dufresne <[email protected]>
---
drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
index f703c585d91c5..f0bc118021b0a 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
@@ -227,6 +227,7 @@ static void cedrus_h265_pred_weight_write(struct cedrus_dev *dev,
static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
{
int count = 0;
+ u32 reg;

while (count < num) {
int tmp = min(num - count, 32);
@@ -234,8 +235,9 @@ static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
cedrus_write(dev, VE_DEC_H265_TRIGGER,
VE_DEC_H265_TRIGGER_FLUSH_BITS |
VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
- while (cedrus_read(dev, VE_DEC_H265_STATUS) & VE_DEC_H265_STATUS_VLD_BUSY)
- udelay(1);
+
+ if (cedrus_wait_for(dev, VE_DEC_H265_STATUS, VE_DEC_H265_STATUS_VLD_BUSY))
+ dev_err_ratelimited(dev->dev, "timed out waiting to skip bits\n");

count += tmp;
}
--
2.37.2

2022-08-18 22:04:28

by Nicolas Dufresne

Subject: Re: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()

Le jeudi 18 août 2022 à 23:39 +0300, Dmitry Osipenko a écrit :
> On 8/18/22 23:33, Nicolas Dufresne wrote:
> > From: Dmitry Osipenko <[email protected]>
> >
> > The busy status bit may never de-assert if number of programmed skip
> > bits is incorrect, resulting in a kernel hang because the bit is polled
> > endlessly in the code. Fix it by adding timeout for the bit-polling.
> > This problem is reproducible by setting the data_bit_offset field of
> > the HEVC slice params to a wrong value by userspace.
> >
> > Cc: [email protected]
> > Reported-by: Nicolas Dufresne <[email protected]>
> > Signed-off-by: Dmitry Osipenko <[email protected]>
> > Signed-off-by: Nicolas Dufresne <[email protected]>
> > ---
> > drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > index f703c585d91c5..f0bc118021b0a 100644
> > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > @@ -227,6 +227,7 @@ static void cedrus_h265_pred_weight_write(struct cedrus_dev *dev,
> > static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
> > {
> > int count = 0;
> > + u32 reg;
>
> This "reg" variable isn't needed anymore after switching to
> cedrus_wait_for(). Sorry, I missed it :)

Good catch thanks, will fix.

>
> > while (count < num) {
> > int tmp = min(num - count, 32);
> > @@ -234,8 +235,9 @@ static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
> > cedrus_write(dev, VE_DEC_H265_TRIGGER,
> > VE_DEC_H265_TRIGGER_FLUSH_BITS |
> > VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
> > - while (cedrus_read(dev, VE_DEC_H265_STATUS) & VE_DEC_H265_STATUS_VLD_BUSY)
> > - udelay(1);
> > +
> > + if (cedrus_wait_for(dev, VE_DEC_H265_STATUS, VE_DEC_H265_STATUS_VLD_BUSY))
> > + dev_err_ratelimited(dev->dev, "timed out waiting to skip bits\n");
> >
> > count += tmp;
> > }
>
>

2022-08-18 22:04:33

by Dmitry Osipenko

Subject: Re: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()

On 8/18/22 23:33, Nicolas Dufresne wrote:
> From: Dmitry Osipenko <[email protected]>
>
> The busy status bit may never de-assert if number of programmed skip
> bits is incorrect, resulting in a kernel hang because the bit is polled
> endlessly in the code. Fix it by adding timeout for the bit-polling.
> This problem is reproducible by setting the data_bit_offset field of
> the HEVC slice params to a wrong value by userspace.
>
> Cc: [email protected]
> Reported-by: Nicolas Dufresne <[email protected]>
> Signed-off-by: Dmitry Osipenko <[email protected]>
> Signed-off-by: Nicolas Dufresne <[email protected]>
> ---
> drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> index f703c585d91c5..f0bc118021b0a 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> @@ -227,6 +227,7 @@ static void cedrus_h265_pred_weight_write(struct cedrus_dev *dev,
> static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
> {
> int count = 0;
> + u32 reg;

This "reg" variable isn't needed anymore after switching to
cedrus_wait_for(). Sorry, I missed it :)

> while (count < num) {
> int tmp = min(num - count, 32);
> @@ -234,8 +235,9 @@ static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
> cedrus_write(dev, VE_DEC_H265_TRIGGER,
> VE_DEC_H265_TRIGGER_FLUSH_BITS |
> VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
> - while (cedrus_read(dev, VE_DEC_H265_STATUS) & VE_DEC_H265_STATUS_VLD_BUSY)
> - udelay(1);
> +
> + if (cedrus_wait_for(dev, VE_DEC_H265_STATUS, VE_DEC_H265_STATUS_VLD_BUSY))
> + dev_err_ratelimited(dev->dev, "timed out waiting to skip bits\n");
>
> count += tmp;
> }


--
Best regards,
Dmitry

2022-08-19 04:47:02

by Jernej Škrabec

Subject: Re: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()

Dne četrtek, 18. avgust 2022 ob 22:33:08 CEST je Nicolas Dufresne napisal(a):
> From: Dmitry Osipenko <[email protected]>
>
> The busy status bit may never de-assert if number of programmed skip
> bits is incorrect, resulting in a kernel hang because the bit is polled
> endlessly in the code. Fix it by adding timeout for the bit-polling.
> This problem is reproducible by setting the data_bit_offset field of
> the HEVC slice params to a wrong value by userspace.
>
> Cc: [email protected]
> Reported-by: Nicolas Dufresne <[email protected]>
> Signed-off-by: Dmitry Osipenko <[email protected]>
> Signed-off-by: Nicolas Dufresne <[email protected]>

Fixes tag would be nice.

> ---
> drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c index
> f703c585d91c5..f0bc118021b0a 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> @@ -227,6 +227,7 @@ static void cedrus_h265_pred_weight_write(struct
> cedrus_dev *dev, static void cedrus_h265_skip_bits(struct cedrus_dev *dev,
> int num) {
> int count = 0;
> + u32 reg;
>
> while (count < num) {
> int tmp = min(num - count, 32);
> @@ -234,8 +235,9 @@ static void cedrus_h265_skip_bits(struct cedrus_dev
> *dev, int num) cedrus_write(dev, VE_DEC_H265_TRIGGER,
> VE_DEC_H265_TRIGGER_FLUSH_BITS |
> VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
> - while (cedrus_read(dev, VE_DEC_H265_STATUS) &
> VE_DEC_H265_STATUS_VLD_BUSY) - udelay(1);
> +
> + if (cedrus_wait_for(dev, VE_DEC_H265_STATUS,
> VE_DEC_H265_STATUS_VLD_BUSY)) +
dev_err_ratelimited(dev->dev, "timed out
> waiting to skip bits\n");

Reporting issue is nice, but better would be to propagate error, since there
is no way to properly decode this slice if above code block fails.

Best regards,
Jernej

>
> count += tmp;
> }

2022-08-19 15:42:01

by Nicolas Dufresne

Subject: Re: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()

Le vendredi 19 août 2022 à 06:16 +0200, Jernej Škrabec a écrit :
> Dne četrtek, 18. avgust 2022 ob 22:33:08 CEST je Nicolas Dufresne napisal(a):
> > From: Dmitry Osipenko <[email protected]>
> >
> > The busy status bit may never de-assert if number of programmed skip
> > bits is incorrect, resulting in a kernel hang because the bit is polled
> > endlessly in the code. Fix it by adding timeout for the bit-polling.
> > This problem is reproducible by setting the data_bit_offset field of
> > the HEVC slice params to a wrong value by userspace.
> >
> > Cc: [email protected]
> > Reported-by: Nicolas Dufresne <[email protected]>
> > Signed-off-by: Dmitry Osipenko <[email protected]>
> > Signed-off-by: Nicolas Dufresne <[email protected]>
>
> Fixes tag would be nice.
>
> > ---
> > drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c index
> > f703c585d91c5..f0bc118021b0a 100644
> > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > @@ -227,6 +227,7 @@ static void cedrus_h265_pred_weight_write(struct
> > cedrus_dev *dev, static void cedrus_h265_skip_bits(struct cedrus_dev *dev,
> > int num) {
> > int count = 0;
> > + u32 reg;
> >
> > while (count < num) {
> > int tmp = min(num - count, 32);
> > @@ -234,8 +235,9 @@ static void cedrus_h265_skip_bits(struct cedrus_dev
> > *dev, int num) cedrus_write(dev, VE_DEC_H265_TRIGGER,
> > VE_DEC_H265_TRIGGER_FLUSH_BITS |
> > VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
> > - while (cedrus_read(dev, VE_DEC_H265_STATUS) &
> > VE_DEC_H265_STATUS_VLD_BUSY) - udelay(1);
> > +
> > + if (cedrus_wait_for(dev, VE_DEC_H265_STATUS,
> > VE_DEC_H265_STATUS_VLD_BUSY)) +
> dev_err_ratelimited(dev->dev, "timed out
> > waiting to skip bits\n");
>
> Reporting issue is nice, but better would be to propagate error, since there
> is no way to properly decode this slice if above code block fails.

This mimic what was already there, mind if we do that later ? The propagation is
doing to be a lot more intrusive.

>
> Best regards,
> Jernej
>
> >
> > count += tmp;
> > }
>
>
>
>

2022-08-25 21:47:04

by Jernej Škrabec

Subject: Re: Re: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()

Dne petek, 19. avgust 2022 ob 17:39:25 CEST je Nicolas Dufresne napisal(a):
> Le vendredi 19 août 2022 à 06:16 +0200, Jernej Škrabec a écrit :
> > Dne četrtek, 18. avgust 2022 ob 22:33:08 CEST je Nicolas Dufresne
napisal(a):
> > > From: Dmitry Osipenko <[email protected]>
> > >
> > > The busy status bit may never de-assert if number of programmed skip
> > > bits is incorrect, resulting in a kernel hang because the bit is polled
> > > endlessly in the code. Fix it by adding timeout for the bit-polling.
> > > This problem is reproducible by setting the data_bit_offset field of
> > > the HEVC slice params to a wrong value by userspace.
> > >
> > > Cc: [email protected]
> > > Reported-by: Nicolas Dufresne <[email protected]>
> > > Signed-off-by: Dmitry Osipenko <[email protected]>
> > > Signed-off-by: Nicolas Dufresne <[email protected]>
> >
> > Fixes tag would be nice.
> >
> > > ---
> > >
> > > drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
> > > 1 file changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > > b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c index
> > > f703c585d91c5..f0bc118021b0a 100644
> > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > > @@ -227,6 +227,7 @@ static void cedrus_h265_pred_weight_write(struct
> > > cedrus_dev *dev, static void cedrus_h265_skip_bits(struct cedrus_dev
> > > *dev,
> > > int num) {
> > >
> > > int count = 0;
> > >
> > > + u32 reg;
> > >
> > > while (count < num) {
> > >
> > > int tmp = min(num - count, 32);
> > >
> > > @@ -234,8 +235,9 @@ static void cedrus_h265_skip_bits(struct cedrus_dev
> > > *dev, int num) cedrus_write(dev, VE_DEC_H265_TRIGGER,
> > >
> > > VE_DEC_H265_TRIGGER_FLUSH_BITS |
> > > VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
> > >
> > > - while (cedrus_read(dev, VE_DEC_H265_STATUS) &
> > > VE_DEC_H265_STATUS_VLD_BUSY) - udelay(1);
> > > +
> > > + if (cedrus_wait_for(dev, VE_DEC_H265_STATUS,
> > > VE_DEC_H265_STATUS_VLD_BUSY)) +
> >
> > dev_err_ratelimited(dev->dev, "timed out
> >
> > > waiting to skip bits\n");
> >
> > Reporting issue is nice, but better would be to propagate error, since
> > there is no way to properly decode this slice if above code block fails.
> This mimic what was already there, mind if we do that later ? The
> propagation is doing to be a lot more intrusive.

Since backporting fixes before 6.0 isn't priority, viability for backpporting
isn't that important. You would only need to return 0 or -ETIMEDOUT and check
for error in only one location. That doesn't sound very intrusive for me.

Best regards,
Jernej

>
> > Best regards,
> > Jernej
> >
> > > count += tmp;
> > >
> > > }