RE: [PATCH 6.0 681/862] wifi: rtw88: phy: fix warning of possible buffer overflow

[Ping-Ke Shih]

> -----Original Message-----
> From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Sent: Wednesday, October 19, 2022 4:33 PM
> To: linux-kernel@xxxxxxxxxxxxxxx
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; stable@xxxxxxxxxxxxxxx; Kevin Yang
> <kevin_yang@xxxxxxxxxxx>; Ping-Ke Shih <pkshih@xxxxxxxxxxx>; Kalle Valo <kvalo@xxxxxxxxxx>; Sasha Levin
> <sashal@xxxxxxxxxx>
> Subject: [PATCH 6.0 681/862] wifi: rtw88: phy: fix warning of possible buffer overflow
> 
> From: Zong-Zhe Yang <kevin_yang@xxxxxxxxxxx>
> 
> [ Upstream commit 86331c7e0cd819bf0c1d0dcf895e0c90b0aa9a6f ]
> 
> reported by smatch
> 
> phy.c:854 rtw_phy_linear_2_db() error: buffer overflow 'db_invert_table[i]'
> 8 <= 8 (assuming for loop doesn't break)
> 
> However, it seems to be a false alarm because we prevent it originally via
>        if (linear >= db_invert_table[11][7])
>                return 96; /* maximum 96 dB */
> 
> Still, we adjust the code to be more readable and avoid smatch warning.

Like Pavel mentioned [1], this patch is to avoid smatch warning, not a really
bug. So, shouldn't take this patch. 

[1] https://lore.kernel.org/linux-wireless/20221018093921.GD1264@xxxxxxxxxx/

> 
> Signed-off-by: Zong-Zhe Yang <kevin_yang@xxxxxxxxxxx>
> Signed-off-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>
> Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20220727065003.28340-5-pkshih@xxxxxxxxxxx
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>  drivers/net/wireless/realtek/rtw88/phy.c | 21 ++++++++-------------
>  1 file changed, 8 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtw88/phy.c b/drivers/net/wireless/realtek/rtw88/phy.c
> index 8982e0c98dac..da1efec0aa85 100644
> --- a/drivers/net/wireless/realtek/rtw88/phy.c
> +++ b/drivers/net/wireless/realtek/rtw88/phy.c
> @@ -816,23 +816,18 @@ static u8 rtw_phy_linear_2_db(u64 linear)
>  	u8 j;
>  	u32 dB;
> 
> -	if (linear >= db_invert_table[11][7])
> -		return 96; /* maximum 96 dB */
> -
>  	for (i = 0; i < 12; i++) {
> -		if (i <= 2 && (linear << FRAC_BITS) <= db_invert_table[i][7])
> -			break;
> -		else if (i > 2 && linear <= db_invert_table[i][7])
> -			break;
> +		for (j = 0; j < 8; j++) {
> +			if (i <= 2 && (linear << FRAC_BITS) <= db_invert_table[i][j])
> +				goto cnt;
> +			else if (i > 2 && linear <= db_invert_table[i][j])
> +				goto cnt;
> +		}
>  	}
> 
> -	for (j = 0; j < 8; j++) {
> -		if (i <= 2 && (linear << FRAC_BITS) <= db_invert_table[i][j])
> -			break;
> -		else if (i > 2 && linear <= db_invert_table[i][j])
> -			break;
> -	}
> +	return 96; /* maximum 96 dB */
> 
> +cnt:
>  	if (j == 0 && i == 0)
>  		goto end;
> 
> --
> 2.35.1
> 
> 
> 
> 
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