2024-03-12 09:50:54

by Roman Smirnov

Subject: [PATCH] fixp-arith: prevent division by zero in fixp_sin32_rad()

The parameter twopi can have a zero value. It is necessary
to prevent division by zero.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Signed-off-by: Roman Smirnov <[email protected]>
---
include/linux/fixp-arith.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/fixp-arith.h b/include/linux/fixp-arith.h
index e485fb0c1201..434eee8bd9ef 100644
--- a/include/linux/fixp-arith.h
+++ b/include/linux/fixp-arith.h
@@ -118,8 +118,9 @@ static inline s32 fixp_sin32_rad(u32 radians, u32 twopi)

/*
* Avoid too large values for twopi, as we don't want overflows.
+ * Also prevent division by zero.
*/
- BUG_ON(twopi > 1 << 18);
+ BUG_ON(!twopi || twopi > 1 << 18);

degrees = (radians * 360) / twopi;
tmp = radians - (degrees * twopi) / 360;
--
2.34.1

2024-03-13 19:13:38

by Sergey Shtylyov

Subject: Re: [PATCH] fixp-arith: prevent division by zero in fixp_sin32_rad()

On 3/12/24 12:48 PM, Roman Smirnov wrote:

> The parameter twopi can have a zero value. It is necessary
> to prevent division by zero.
>
> Found by Linux Verification Center (linuxtesting.org) with Svace.
>
> Signed-off-by: Roman Smirnov <[email protected]>
> ---
> include/linux/fixp-arith.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/fixp-arith.h b/include/linux/fixp-arith.h
> index e485fb0c1201..434eee8bd9ef 100644
> --- a/include/linux/fixp-arith.h
> +++ b/include/linux/fixp-arith.h
> @@ -118,8 +118,9 @@ static inline s32 fixp_sin32_rad(u32 radians, u32 twopi)
>
> /*
> * Avoid too large values for twopi, as we don't want overflows.
> + * Also prevent division by zero.
> */
> - BUG_ON(twopi > 1 << 18);
> + BUG_ON(!twopi || twopi > 1 << 18);

Not really sure ATM that BUG_ON() is better than division by 0
(which should cause exception 0 on x86 but I'm not sure about e.g.
ARM32/64)...

>
> degrees = (radians * 360) / twopi;
> tmp = radians - (degrees * twopi) / 360;
>

Reviewed-by: Sergey Shtylyov <[email protected]>

[...]

MBR, Sergey