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* [PATCH][next] i2c: mediatek: fix integer overflow on an integer multiplication
@ 2020-05-18 16:55 Colin King
  2020-05-18 16:59 ` Wolfram Sang
  0 siblings, 1 reply; 3+ messages in thread
From: Colin King @ 2020-05-18 16:55 UTC (permalink / raw)
  To: Matthias Brugger, Wolfram Sang, linux-i2c, linux-arm-kernel,
	linux-mediatek
  Cc: kernel-janitors, linux-kernel

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

Currently the calculation of sample_ns is using a 32 bit integer
multiplication and can potentially overflow. Fix this by making the
constant a long long to use a 64 bit multiply and hence
avoid an overflow.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: 5f1ae73d538a ("i2c: mediatek: Add i2c ac-timing adjust support")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/i2c/busses/i2c-mt65xx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
index 702061805925..c93492b997ce 100644
--- a/drivers/i2c/busses/i2c-mt65xx.c
+++ b/drivers/i2c/busses/i2c-mt65xx.c
@@ -551,7 +551,7 @@ static int mtk_i2c_check_ac_timing(struct mtk_i2c *i2c,
 	const struct i2c_spec_values *spec;
 	unsigned int su_sta_cnt, low_cnt, high_cnt, max_step_cnt;
 	unsigned int sda_max, sda_min, clk_ns, max_sta_cnt = 0x3f;
-	long long sample_ns = (1000000000 * (sample_cnt + 1)) / clk_src;
+	long long sample_ns = (1000000000LL * (sample_cnt + 1)) / clk_src;
 
 	if (!i2c->dev_comp->timing_adjust)
 		return 0;
-- 
2.25.1


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH][next] i2c: mediatek: fix integer overflow on an integer multiplication
  2020-05-18 16:55 [PATCH][next] i2c: mediatek: fix integer overflow on an integer multiplication Colin King
@ 2020-05-18 16:59 ` Wolfram Sang
  2020-05-18 17:11   ` Joe Perches
  0 siblings, 1 reply; 3+ messages in thread
From: Wolfram Sang @ 2020-05-18 16:59 UTC (permalink / raw)
  To: Colin King, qii.wang
  Cc: Matthias Brugger, linux-i2c, linux-arm-kernel, linux-mediatek,
	kernel-janitors, linux-kernel


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On Mon, May 18, 2020 at 05:55:29PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> Currently the calculation of sample_ns is using a 32 bit integer
> multiplication and can potentially overflow. Fix this by making the
> constant a long long to use a 64 bit multiply and hence
> avoid an overflow.
> 
> Addresses-Coverity: ("Unintentional integer overflow")
> Fixes: 5f1ae73d538a ("i2c: mediatek: Add i2c ac-timing adjust support")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

CCing the patch author.

> ---
>  drivers/i2c/busses/i2c-mt65xx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> index 702061805925..c93492b997ce 100644
> --- a/drivers/i2c/busses/i2c-mt65xx.c
> +++ b/drivers/i2c/busses/i2c-mt65xx.c
> @@ -551,7 +551,7 @@ static int mtk_i2c_check_ac_timing(struct mtk_i2c *i2c,
>  	const struct i2c_spec_values *spec;
>  	unsigned int su_sta_cnt, low_cnt, high_cnt, max_step_cnt;
>  	unsigned int sda_max, sda_min, clk_ns, max_sta_cnt = 0x3f;
> -	long long sample_ns = (1000000000 * (sample_cnt + 1)) / clk_src;
> +	long long sample_ns = (1000000000LL * (sample_cnt + 1)) / clk_src;
>  
>  	if (!i2c->dev_comp->timing_adjust)
>  		return 0;
> -- 
> 2.25.1
> 

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH][next] i2c: mediatek: fix integer overflow on an integer multiplication
  2020-05-18 16:59 ` Wolfram Sang
@ 2020-05-18 17:11   ` Joe Perches
  0 siblings, 0 replies; 3+ messages in thread
From: Joe Perches @ 2020-05-18 17:11 UTC (permalink / raw)
  To: Wolfram Sang, Colin King, qii.wang
  Cc: Matthias Brugger, linux-i2c, linux-arm-kernel, linux-mediatek,
	kernel-janitors, linux-kernel

On Mon, 2020-05-18 at 18:59 +0200, Wolfram Sang wrote:
> On Mon, May 18, 2020 at 05:55:29PM +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@canonical.com>
> > 
> > Currently the calculation of sample_ns is using a 32 bit integer
> > multiplication and can potentially overflow. Fix this by making the
> > constant a long long to use a 64 bit multiply and hence
> > avoid an overflow.
> > 
> > Addresses-Coverity: ("Unintentional integer overflow")
> > Fixes: 5f1ae73d538a ("i2c: mediatek: Add i2c ac-timing adjust support")
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> 
> CCing the patch author.
> 
> > ---
> >  drivers/i2c/busses/i2c-mt65xx.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> > index 702061805925..c93492b997ce 100644
> > --- a/drivers/i2c/busses/i2c-mt65xx.c
> > +++ b/drivers/i2c/busses/i2c-mt65xx.c
> > @@ -551,7 +551,7 @@ static int mtk_i2c_check_ac_timing(struct mtk_i2c *i2c,
> >  	const struct i2c_spec_values *spec;
> >  	unsigned int su_sta_cnt, low_cnt, high_cnt, max_step_cnt;
> >  	unsigned int sda_max, sda_min, clk_ns, max_sta_cnt = 0x3f;
> > -	long long sample_ns = (1000000000 * (sample_cnt + 1)) / clk_src;
> > +	long long sample_ns = (1000000000LL * (sample_cnt + 1)) / clk_src;

unsigned long long?



^ permalink raw reply	[flat|nested] 3+ messages in thread

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2020-05-18 16:55 [PATCH][next] i2c: mediatek: fix integer overflow on an integer multiplication Colin King
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2020-05-18 17:11   ` Joe Perches

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