Re: [PATCH 6.1.y] HID: core: Harden s32ton() against conversion to 0 bits

[syzbot <syzbot+b63d677d63bcac06cf90@syzkaller.appspotmail.com>]

> #syz test: 

This bug is already marked as fixed. No point in testing.

> git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git linux-6.1.y
>
> drivers/hid/hid-core.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index ed65523d77c2..c8cca0c7ec67 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -1354,7 +1354,12 @@ EXPORT_SYMBOL_GPL(hid_snto32);
>
>   static u32 s32ton(__s32 value, unsigned n)
>   {
> -    s32 a = value >> (n - 1);
> +    s32 a;
> +    if (!value || !n)
> +        return 0;
> +
> +    a = value >> (n - 1);
> +
>       if (a && a != -1)
>           return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1;
>       return value & ((1 << n) - 1);
> -- 
> 2.43.0
>
>