linux-kernel - Re: [PATCH] rtlwifi: rtl8192de: Fix initialization of place in _rtl92c_phy_get

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Date:   Wed, 25 Aug 2021 19:36:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Ping-Ke Shih <pkshih@...ltek.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Colin Ian King <colin.king@...onical.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] rtlwifi: rtl8192de: Fix initialization of place in
 _rtl92c_phy_get_rightchnlplace()

On Mon, Aug 23, 2021 at 03:20:14PM -0700, Nathan Chancellor wrote:
> Clang warns:
> 
> drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c:901:6: warning:
> variable 'place' is used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>         if (chnl > 14) {
>             ^~~~~~~~~
> drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c:909:9: note:
> uninitialized use occurs here
>         return place;
>                ^~~~~
> drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c:901:2: note: remove
> the 'if' if its condition is always true
>         if (chnl > 14) {
>         ^~~~~~~~~~~~~~~
> drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c:899:10: note:
> initialize the variable 'place' to silence this warning
>         u8 place;
>                 ^
>                  = '\0'
> 1 warning generated.
> 
> Commit 369956ae5720 ("rtlwifi: rtl8192de: Remove redundant variable
> initializations") removed the initialization of place but it appears
> that this removal was in the wrong function.
> 
> _rtl92c_phy_get_rightchnlplace() returns place's value at the end of the
> function so now if the if statement is false, place never gets
> initialized. Add that initialization back to address the warning.
> 
> place's initialization is not necessary in
> rtl92d_get_rightchnlplace_for_iqk() as place is only used within the if
> statement so it can be removed, which is likely what was intended in the
> first place.
> 
> Fixes: 369956ae5720 ("rtlwifi: rtl8192de: Remove redundant variable initializations")
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

Thanks, I tripped over this too.

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c
> index 8ae69d914312..9b83c710c9b8 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c
> @@ -896,7 +896,7 @@ static void _rtl92d_ccxpower_index_check(struct ieee80211_hw *hw,
>  
>  static u8 _rtl92c_phy_get_rightchnlplace(u8 chnl)
>  {
> -	u8 place;
> +	u8 place = chnl;
>  
>  	if (chnl > 14) {
>  		for (place = 14; place < sizeof(channel5g); place++) {
> @@ -1363,7 +1363,7 @@ static void _rtl92d_phy_switch_rf_setting(struct ieee80211_hw *hw, u8 channel)
>  
>  u8 rtl92d_get_rightchnlplace_for_iqk(u8 chnl)
>  {
> -	u8 place = chnl;
> +	u8 place;
>  
>  	if (chnl > 14) {
>  		for (place = 14; place < sizeof(channel_all); place++) {
> 
> base-commit: 609c1308fbc6446fd6d8fec42b80e157768a5362
> -- 
> 2.33.0
> 

-- 
Kees Cook