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* [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply
@ 2019-10-22 11:49 Colin King
  2019-10-22 12:46 ` walter harms
  2019-10-29 19:40 ` Daniel Lezcano
  0 siblings, 2 replies; 4+ messages in thread
From: Colin King @ 2019-10-22 11:49 UTC (permalink / raw)
  To: Amit Kucheria, Andy Gross, Zhang Rui, Eduardo Valentin,
	Daniel Lezcano, Stephen Boyd, linux-pm, linux-arm-msm
  Cc: kernel-janitors, linux-kernel

From: Colin Ian King <colin.king@canonical.com>

Currently a multiply operation is being performed on two int values
and the result is being assigned to a u64, presumably because the
end result is expected to be probably larger than an int. However,
because the multiply is an int multiply one can get overflow. Avoid
the overflow by casting degc to a u64 to force a u64 multiply.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: fbfe1a042cfd ("drivers: thermal: tsens: Add interrupt support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/thermal/qcom/tsens-common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/thermal/qcom/tsens-common.c b/drivers/thermal/qcom/tsens-common.c
index 03bf1b8133ea..3d7855106ecd 100644
--- a/drivers/thermal/qcom/tsens-common.c
+++ b/drivers/thermal/qcom/tsens-common.c
@@ -92,7 +92,7 @@ void compute_intercept_slope(struct tsens_priv *priv, u32 *p1,
 
 static inline u32 degc_to_code(int degc, const struct tsens_sensor *s)
 {
-	u64 code = (degc * s->slope + s->offset) / SLOPE_FACTOR;
+	u64 code = ((u64)degc * s->slope + s->offset) / SLOPE_FACTOR;
 
 	pr_debug("%s: raw_code: 0x%llx, degc:%d\n", __func__, code, degc);
 	return clamp_val(code, THRESHOLD_MIN_ADC_CODE, THRESHOLD_MAX_ADC_CODE);
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 4+ messages in thread
* Re: [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply
  2019-10-22 11:49 [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply Colin King
@ 2019-10-22 12:46 ` walter harms
  2019-10-29 19:40 ` Daniel Lezcano
  1 sibling, 0 replies; 4+ messages in thread
From: walter harms @ 2019-10-22 12:46 UTC (permalink / raw)
  To: Colin King
  Cc: Amit Kucheria, Andy Gross, Zhang Rui, Eduardo Valentin,
	Daniel Lezcano, Stephen Boyd, linux-pm, linux-arm-msm,
	kernel-janitors, linux-kernel



Am 22.10.2019 13:49, schrieb Colin King:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently a multiply operation is being performed on two int values
> and the result is being assigned to a u64, presumably because the
> end result is expected to be probably larger than an int. However,
> because the multiply is an int multiply one can get overflow. Avoid
> the overflow by casting degc to a u64 to force a u64 multiply.
> 
> Addresses-Coverity: ("Unintentional integer overflow")
> Fixes: fbfe1a042cfd ("drivers: thermal: tsens: Add interrupt support")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/thermal/qcom/tsens-common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/qcom/tsens-common.c b/drivers/thermal/qcom/tsens-common.c
> index 03bf1b8133ea..3d7855106ecd 100644
> --- a/drivers/thermal/qcom/tsens-common.c
> +++ b/drivers/thermal/qcom/tsens-common.c
> @@ -92,7 +92,7 @@ void compute_intercept_slope(struct tsens_priv *priv, u32 *p1,
>  
>  static inline u32 degc_to_code(int degc, const struct tsens_sensor *s)
>  {
> -	u64 code = (degc * s->slope + s->offset) / SLOPE_FACTOR;
> +	u64 code = ((u64)degc * s->slope + s->offset) / SLOPE_FACTOR;
>  
looks ok
just to offer an alternative to avoid the cast;
	u64 code = degc;

	code = code * s->slope + s->offset;
	code/=SLOPE_FACTOR;

ym2c
re,
wh


>  	pr_debug("%s: raw_code: 0x%llx, degc:%d\n", __func__, code, degc);
>  	return clamp_val(code, THRESHOLD_MIN_ADC_CODE, THRESHOLD_MAX_ADC_CODE);

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply
  2019-10-22 11:49 [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply Colin King
  2019-10-22 12:46 ` walter harms
@ 2019-10-29 19:40 ` Daniel Lezcano
  2019-10-30 12:52   ` Amit Kucheria
  1 sibling, 1 reply; 4+ messages in thread
From: Daniel Lezcano @ 2019-10-29 19:40 UTC (permalink / raw)
  To: Colin King, Amit Kucheria, Andy Gross, Zhang Rui,
	Eduardo Valentin, Stephen Boyd, linux-pm, linux-arm-msm
  Cc: kernel-janitors, linux-kernel

On 22/10/2019 13:49, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently a multiply operation is being performed on two int values
> and the result is being assigned to a u64, presumably because the
> end result is expected to be probably larger than an int. However,
> because the multiply is an int multiply one can get overflow. Avoid
> the overflow by casting degc to a u64 to force a u64 multiply.
> 
> Addresses-Coverity: ("Unintentional integer overflow")
> Fixes: fbfe1a042cfd ("drivers: thermal: tsens: Add interrupt support")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/thermal/qcom/tsens-common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/qcom/tsens-common.c b/drivers/thermal/qcom/tsens-common.c
> index 03bf1b8133ea..3d7855106ecd 100644
> --- a/drivers/thermal/qcom/tsens-common.c
> +++ b/drivers/thermal/qcom/tsens-common.c
> @@ -92,7 +92,7 @@ void compute_intercept_slope(struct tsens_priv *priv, u32 *p1,
>  
>  static inline u32 degc_to_code(int degc, const struct tsens_sensor *s)
>  {
> -	u64 code = (degc * s->slope + s->offset) / SLOPE_FACTOR;
> +	u64 code = ((u64)degc * s->slope + s->offset) / SLOPE_FACTOR;


-       u64 code = ((u64)degc * s->slope + s->offset) / SLOPE_FACTOR;
+       u64 code = div_u64(((u64)degc * s->slope + s->offset),
SLOPE_FACTOR);


>  
>  	pr_debug("%s: raw_code: 0x%llx, degc:%d\n", __func__, code, degc);
>  	return clamp_val(code, THRESHOLD_MIN_ADC_CODE, THRESHOLD_MAX_ADC_CODE);
> 


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^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply
  2019-10-29 19:40 ` Daniel Lezcano
@ 2019-10-30 12:52   ` Amit Kucheria
  0 siblings, 0 replies; 4+ messages in thread
From: Amit Kucheria @ 2019-10-30 12:52 UTC (permalink / raw)
  To: Daniel Lezcano
  Cc: Colin King, Andy Gross, Zhang Rui, Eduardo Valentin,
	Stephen Boyd, Linux PM list, linux-arm-msm, kernel-janitors,
	LKML

On Wed, Oct 30, 2019 at 1:10 AM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> On 22/10/2019 13:49, Colin King wrote:
> > From: Colin Ian King <colin.king@canonical.com>
> >
> > Currently a multiply operation is being performed on two int values
> > and the result is being assigned to a u64, presumably because the
> > end result is expected to be probably larger than an int. However,
> > because the multiply is an int multiply one can get overflow. Avoid
> > the overflow by casting degc to a u64 to force a u64 multiply.
> >
> > Addresses-Coverity: ("Unintentional integer overflow")
> > Fixes: fbfe1a042cfd ("drivers: thermal: tsens: Add interrupt support")
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> > ---
> >  drivers/thermal/qcom/tsens-common.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/thermal/qcom/tsens-common.c b/drivers/thermal/qcom/tsens-common.c
> > index 03bf1b8133ea..3d7855106ecd 100644
> > --- a/drivers/thermal/qcom/tsens-common.c
> > +++ b/drivers/thermal/qcom/tsens-common.c
> > @@ -92,7 +92,7 @@ void compute_intercept_slope(struct tsens_priv *priv, u32 *p1,
> >
> >  static inline u32 degc_to_code(int degc, const struct tsens_sensor *s)
> >  {
> > -     u64 code = (degc * s->slope + s->offset) / SLOPE_FACTOR;
> > +     u64 code = ((u64)degc * s->slope + s->offset) / SLOPE_FACTOR;
>
>
> -       u64 code = ((u64)degc * s->slope + s->offset) / SLOPE_FACTOR;
> +       u64 code = div_u64(((u64)degc * s->slope + s->offset),
> SLOPE_FACTOR);

This implementation should handle 32-bit architectures too. Colin,
could you respin?

Regards,
Amit

^ permalink raw reply	[flat|nested] 4+ messages in thread
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2019-10-22 11:49 [PATCH][next] drivers: thermal: tsens: fix potential integer overflow on multiply Colin King
2019-10-22 12:46 ` walter harms
2019-10-29 19:40 ` Daniel Lezcano
2019-10-30 12:52   ` Amit Kucheria

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