[04/25] iio:light:st_uvis25 Fix timestamp alignment and prevent data leak.
diff mbox series

Message ID 20200525170628.503283-5-jic23@kernel.org
State New
Headers show
Series
  • IIO: 2nd set of timestamp alignment fixes.
Related show

Commit Message

Jonathan Cameron May 25, 2020, 5:06 p.m. UTC
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

One of a class of bugs pointed out by Lars in a recent review.
iio_push_to_buffers_with_timestamp assumes the buffer used is aligned
to the size of the timestamp (8 bytes).  This is not guaranteed in
this driver which uses an array of smaller elements on the stack.
As Lars also noted this anti pattern can involve a leak of data to
userspace and that indeed can happen here.  We close both issues by
moving to a suitable structure in the iio_priv()

This data is allocated with kzalloc so no data can leak apart
from previous readings.

Fixes: 3025c8688c1e ("iio: light: add support for UVIS25 sensor")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
---
 drivers/iio/light/st_uvis25.h      | 5 +++++
 drivers/iio/light/st_uvis25_core.c | 6 +++---
 2 files changed, 8 insertions(+), 3 deletions(-)

Comments

Lorenzo Bianconi May 26, 2020, 7:55 a.m. UTC | #1
> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> One of a class of bugs pointed out by Lars in a recent review.
> iio_push_to_buffers_with_timestamp assumes the buffer used is aligned
> to the size of the timestamp (8 bytes).  This is not guaranteed in
> this driver which uses an array of smaller elements on the stack.
> As Lars also noted this anti pattern can involve a leak of data to
> userspace and that indeed can happen here.  We close both issues by
> moving to a suitable structure in the iio_priv()
> 
> This data is allocated with kzalloc so no data can leak apart
> from previous readings.
> 
> Fixes: 3025c8688c1e ("iio: light: add support for UVIS25 sensor")
> Reported-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>

Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>

> ---
>  drivers/iio/light/st_uvis25.h      | 5 +++++
>  drivers/iio/light/st_uvis25_core.c | 6 +++---
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/light/st_uvis25.h b/drivers/iio/light/st_uvis25.h
> index 78bc56aad129..f7027e4c4493 100644
> --- a/drivers/iio/light/st_uvis25.h
> +++ b/drivers/iio/light/st_uvis25.h
> @@ -27,6 +27,11 @@ struct st_uvis25_hw {
>  	struct iio_trigger *trig;
>  	bool enabled;
>  	int irq;
> +	/* Ensure timestamp is naturally aligned */
> +	struct {
> +		u8 chan;
> +		s64 ts;
> +	} scan;
>  };
>  
>  extern const struct dev_pm_ops st_uvis25_pm_ops;
> diff --git a/drivers/iio/light/st_uvis25_core.c b/drivers/iio/light/st_uvis25_core.c
> index d262c254b895..fe1f2dc970c7 100644
> --- a/drivers/iio/light/st_uvis25_core.c
> +++ b/drivers/iio/light/st_uvis25_core.c
> @@ -234,17 +234,17 @@ static const struct iio_buffer_setup_ops st_uvis25_buffer_ops = {
>  
>  static irqreturn_t st_uvis25_buffer_handler_thread(int irq, void *p)
>  {
> -	u8 buffer[ALIGN(sizeof(u8), sizeof(s64)) + sizeof(s64)];
>  	struct iio_poll_func *pf = p;
>  	struct iio_dev *iio_dev = pf->indio_dev;
>  	struct st_uvis25_hw *hw = iio_priv(iio_dev);
>  	int err;
>  
> -	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR, (int *)buffer);
> +	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR,
> +			  (unsigned int *)&hw->scan.chan);
>  	if (err < 0)
>  		goto out;
>  
> -	iio_push_to_buffers_with_timestamp(iio_dev, buffer,
> +	iio_push_to_buffers_with_timestamp(iio_dev, &hw->scan,
>  					   iio_get_time_ns(iio_dev));
>  
>  out:
> -- 
> 2.26.2
>
Jonathan Cameron May 26, 2020, 4:53 p.m. UTC | #2
On Tue, 26 May 2020 09:55:05 +0200
Lorenzo Bianconi <lorenzo@kernel.org> wrote:

> > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > 
> > One of a class of bugs pointed out by Lars in a recent review.
> > iio_push_to_buffers_with_timestamp assumes the buffer used is aligned
> > to the size of the timestamp (8 bytes).  This is not guaranteed in
> > this driver which uses an array of smaller elements on the stack.
> > As Lars also noted this anti pattern can involve a leak of data to
> > userspace and that indeed can happen here.  We close both issues by
> > moving to a suitable structure in the iio_priv()
> > 
> > This data is allocated with kzalloc so no data can leak apart
> > from previous readings.
> > 
> > Fixes: 3025c8688c1e ("iio: light: add support for UVIS25 sensor")
> > Reported-by: Lars-Peter Clausen <lars@metafoo.de>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>  
> 
> Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>

Unfortunately this is wrong (as Andy Schevchenko pointed out in one
of the other patches).  On x86_32 s64 is only aligned to 4 bytes
so the size of the structure will end up too small for the IIO alignment
rules.

There will be a v2 once we've figure out the best, consistent solution.

Sorry about that!

Jonathan

> 
> > ---
> >  drivers/iio/light/st_uvis25.h      | 5 +++++
> >  drivers/iio/light/st_uvis25_core.c | 6 +++---
> >  2 files changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/iio/light/st_uvis25.h b/drivers/iio/light/st_uvis25.h
> > index 78bc56aad129..f7027e4c4493 100644
> > --- a/drivers/iio/light/st_uvis25.h
> > +++ b/drivers/iio/light/st_uvis25.h
> > @@ -27,6 +27,11 @@ struct st_uvis25_hw {
> >  	struct iio_trigger *trig;
> >  	bool enabled;
> >  	int irq;
> > +	/* Ensure timestamp is naturally aligned */
> > +	struct {
> > +		u8 chan;
> > +		s64 ts;
> > +	} scan;
> >  };
> >  
> >  extern const struct dev_pm_ops st_uvis25_pm_ops;
> > diff --git a/drivers/iio/light/st_uvis25_core.c b/drivers/iio/light/st_uvis25_core.c
> > index d262c254b895..fe1f2dc970c7 100644
> > --- a/drivers/iio/light/st_uvis25_core.c
> > +++ b/drivers/iio/light/st_uvis25_core.c
> > @@ -234,17 +234,17 @@ static const struct iio_buffer_setup_ops st_uvis25_buffer_ops = {
> >  
> >  static irqreturn_t st_uvis25_buffer_handler_thread(int irq, void *p)
> >  {
> > -	u8 buffer[ALIGN(sizeof(u8), sizeof(s64)) + sizeof(s64)];
> >  	struct iio_poll_func *pf = p;
> >  	struct iio_dev *iio_dev = pf->indio_dev;
> >  	struct st_uvis25_hw *hw = iio_priv(iio_dev);
> >  	int err;
> >  
> > -	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR, (int *)buffer);
> > +	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR,
> > +			  (unsigned int *)&hw->scan.chan);
> >  	if (err < 0)
> >  		goto out;
> >  
> > -	iio_push_to_buffers_with_timestamp(iio_dev, buffer,
> > +	iio_push_to_buffers_with_timestamp(iio_dev, &hw->scan,
> >  					   iio_get_time_ns(iio_dev));
> >  
> >  out:
> > -- 
> > 2.26.2
> >   
>
Jonathan Cameron June 7, 2020, 2:37 p.m. UTC | #3
On Tue, 26 May 2020 17:53:26 +0100
Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:

> On Tue, 26 May 2020 09:55:05 +0200
> Lorenzo Bianconi <lorenzo@kernel.org> wrote:
> 
> > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > 
> > > One of a class of bugs pointed out by Lars in a recent review.
> > > iio_push_to_buffers_with_timestamp assumes the buffer used is aligned
> > > to the size of the timestamp (8 bytes).  This is not guaranteed in
> > > this driver which uses an array of smaller elements on the stack.
> > > As Lars also noted this anti pattern can involve a leak of data to
> > > userspace and that indeed can happen here.  We close both issues by
> > > moving to a suitable structure in the iio_priv()
> > > 
> > > This data is allocated with kzalloc so no data can leak apart
> > > from previous readings.
> > > 
> > > Fixes: 3025c8688c1e ("iio: light: add support for UVIS25 sensor")
> > > Reported-by: Lars-Peter Clausen <lars@metafoo.de>
> > > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>    
> > 
> > Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>  
> 
> Unfortunately this is wrong (as Andy Schevchenko pointed out in one
> of the other patches).  On x86_32 s64 is only aligned to 4 bytes
> so the size of the structure will end up too small for the IIO alignment
> rules.
> 
> There will be a v2 once we've figure out the best, consistent solution.

Given the change is fairly small I've kept acks etc from V1. Hopefully
no one minds that.

Jonathan

> 
> Sorry about that!
> 
> Jonathan
> 
> >   
> > > ---
> > >  drivers/iio/light/st_uvis25.h      | 5 +++++
> > >  drivers/iio/light/st_uvis25_core.c | 6 +++---
> > >  2 files changed, 8 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/iio/light/st_uvis25.h b/drivers/iio/light/st_uvis25.h
> > > index 78bc56aad129..f7027e4c4493 100644
> > > --- a/drivers/iio/light/st_uvis25.h
> > > +++ b/drivers/iio/light/st_uvis25.h
> > > @@ -27,6 +27,11 @@ struct st_uvis25_hw {
> > >  	struct iio_trigger *trig;
> > >  	bool enabled;
> > >  	int irq;
> > > +	/* Ensure timestamp is naturally aligned */
> > > +	struct {
> > > +		u8 chan;
> > > +		s64 ts;
> > > +	} scan;
> > >  };
> > >  
> > >  extern const struct dev_pm_ops st_uvis25_pm_ops;
> > > diff --git a/drivers/iio/light/st_uvis25_core.c b/drivers/iio/light/st_uvis25_core.c
> > > index d262c254b895..fe1f2dc970c7 100644
> > > --- a/drivers/iio/light/st_uvis25_core.c
> > > +++ b/drivers/iio/light/st_uvis25_core.c
> > > @@ -234,17 +234,17 @@ static const struct iio_buffer_setup_ops st_uvis25_buffer_ops = {
> > >  
> > >  static irqreturn_t st_uvis25_buffer_handler_thread(int irq, void *p)
> > >  {
> > > -	u8 buffer[ALIGN(sizeof(u8), sizeof(s64)) + sizeof(s64)];
> > >  	struct iio_poll_func *pf = p;
> > >  	struct iio_dev *iio_dev = pf->indio_dev;
> > >  	struct st_uvis25_hw *hw = iio_priv(iio_dev);
> > >  	int err;
> > >  
> > > -	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR, (int *)buffer);
> > > +	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR,
> > > +			  (unsigned int *)&hw->scan.chan);
> > >  	if (err < 0)
> > >  		goto out;
> > >  
> > > -	iio_push_to_buffers_with_timestamp(iio_dev, buffer,
> > > +	iio_push_to_buffers_with_timestamp(iio_dev, &hw->scan,
> > >  					   iio_get_time_ns(iio_dev));
> > >  
> > >  out:
> > > -- 
> > > 2.26.2
> > >     
> >   
> 
>

Patch
diff mbox series

diff --git a/drivers/iio/light/st_uvis25.h b/drivers/iio/light/st_uvis25.h
index 78bc56aad129..f7027e4c4493 100644
--- a/drivers/iio/light/st_uvis25.h
+++ b/drivers/iio/light/st_uvis25.h
@@ -27,6 +27,11 @@  struct st_uvis25_hw {
 	struct iio_trigger *trig;
 	bool enabled;
 	int irq;
+	/* Ensure timestamp is naturally aligned */
+	struct {
+		u8 chan;
+		s64 ts;
+	} scan;
 };
 
 extern const struct dev_pm_ops st_uvis25_pm_ops;
diff --git a/drivers/iio/light/st_uvis25_core.c b/drivers/iio/light/st_uvis25_core.c
index d262c254b895..fe1f2dc970c7 100644
--- a/drivers/iio/light/st_uvis25_core.c
+++ b/drivers/iio/light/st_uvis25_core.c
@@ -234,17 +234,17 @@  static const struct iio_buffer_setup_ops st_uvis25_buffer_ops = {
 
 static irqreturn_t st_uvis25_buffer_handler_thread(int irq, void *p)
 {
-	u8 buffer[ALIGN(sizeof(u8), sizeof(s64)) + sizeof(s64)];
 	struct iio_poll_func *pf = p;
 	struct iio_dev *iio_dev = pf->indio_dev;
 	struct st_uvis25_hw *hw = iio_priv(iio_dev);
 	int err;
 
-	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR, (int *)buffer);
+	err = regmap_read(hw->regmap, ST_UVIS25_REG_OUT_ADDR,
+			  (unsigned int *)&hw->scan.chan);
 	if (err < 0)
 		goto out;
 
-	iio_push_to_buffers_with_timestamp(iio_dev, buffer,
+	iio_push_to_buffers_with_timestamp(iio_dev, &hw->scan,
 					   iio_get_time_ns(iio_dev));
 
 out: