linux-kernel - Re: [PATCH v2 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <cb551005-eff0-1391-92a0-d956b3d2b930@nfschina.com>
Date:   Fri, 24 Nov 2023 18:06:11 +0800
From:   Su Hui <suhui@...china.com>
To:     Ping-Ke Shih <pkshih@...ltek.com>,
        "dan.carpenter@...aro.org" <dan.carpenter@...aro.org>,
        "kvalo@...nel.org" <kvalo@...nel.org>,
        "nathan@...nel.org" <nathan@...nel.org>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "trix@...hat.com" <trix@...hat.com>
Cc:     "lizetao1@...wei.com" <lizetao1@...wei.com>,
        "linville@...driver.com" <linville@...driver.com>,
        "Larry.Finger@...inger.net" <Larry.Finger@...inger.net>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined
 bitwise shift behavior

On 2023/11/24 16:51, Ping-Ke Shih wrote:
> Subject: [PATCH v2 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior
>
> [...]
>> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
>> b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
>> index 6df270e29e66..52ab1b0761c0 100644
>> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
>> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c
>> @@ -31,7 +31,12 @@ static u32 _rtl8821ae_phy_calculate_bit_shift(u32 bitmask)
>>   {
>>          u32 i = ffs(bitmask);
>>
>> -       return i ? i - 1 : 32;
>> +       if (!i) {
>> +               WARN_ON_ONCE(1);
>> +               return 0;
>> +       }
>> +
>> +       return i - 1;
>>   }
> Personally, I prefer to use __ffs(), because in normal case no need additional '-1',
> and abnormal cases should not happen.

Hi,  Ping-Ke

Replace _rtl8821ae_phy_calculate_bit_shift() by __ffs(bitmask) is better,
but I'm not sure what callers should do when callers check bitmask is 0 before calling.
Maybe this check is useless?

I can send a v3 patch if using  __ffs(bitmask) and no check for bitmask is fine.
Or could you send this patch if you have a better idea?
Thanks for your suggestion!

Su Hui