[lvc-project] [PATCH] wifi: b43: fix cordic arithmetic

[Larry Finger]

On 6/27/23 08:00, Dmitry Antipov wrote:
> In 'lpphy_start_tx_tone()', 'CORDIC_FLOAT((sample.i * max) & 0xFF)'
> is invalid because it is (<32-bit> & 0xff) shifted right by 15 bits
> and so always evaluates to zero. Looking through brcmsmac's
> 'wlc_lcnphy_start_tx_tone()', the result should be masked instead,
> i. e. 'CORDIC_FLOAT(sample[i].max) & 0xFF'.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Suggested-by: Jonas Gorski <jonas.gorski at gmail.com>
> Signed-off-by: Dmitry Antipov <dmantipov at yandex.ru>
> ---
>   drivers/net/wireless/broadcom/b43/phy_lp.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/broadcom/b43/phy_lp.c b/drivers/net/wireless/broadcom/b43/phy_lp.c
> index 0e5c076e7544..e8ef04e509aa 100644
> --- a/drivers/net/wireless/broadcom/b43/phy_lp.c
> +++ b/drivers/net/wireless/broadcom/b43/phy_lp.c
> @@ -1788,8 +1788,8 @@ static void lpphy_start_tx_tone(struct b43_wldev *dev, s32 freq, u16 max)
>   	for (i = 0; i < samples; i++) {
>   		sample = cordic_calc_iq(CORDIC_FIXED(theta));
>   		theta += rotation;
> -		buf[i] = CORDIC_FLOAT((sample.i * max) & 0xFF) << 8;
> -		buf[i] |= CORDIC_FLOAT((sample.q * max) & 0xFF);
> +		buf[i] = (u16)((CORDIC_FLOAT(sample.i * max) & 0xFF) << 8);
> +		buf[i] |= (u16)(CORDIC_FLOAT(sample.q * max) & 0xFF);
>   	}
>   
>   	b43_lptab_write_bulk(dev, B43_LPTAB16(5, 0), samples, buf);

This has not yet been tested, but it does need a "Fixes:" tag, and a Cc for stable.

Larry