linux-kernel - Re: [PATCH] mac80211: initialize variable have_higher_than

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Date:   Thu, 23 Dec 2021 12:30:01 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     trix@...hat.com
Cc:     johannes@...solutions.net, davem@...emloft.net, kuba@...nel.org,
        nathan@...nel.org, linville@...driver.com,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] mac80211: initialize variable have_higher_than_11mbit

On Thu, Dec 23, 2021 at 8:29 AM <trix@...hat.com> wrote:
>
> From: Tom Rix <trix@...hat.com>
>
> Clang static analysis reports this warnings
>
> mlme.c:5332:7: warning: Branch condition evaluates to a
>   garbage value
>     have_higher_than_11mbit)
>     ^~~~~~~~~~~~~~~~~~~~~~~
>
> have_higher_than_11mbit is only set to true some of the time in
> ieee80211_get_rates() but is checked all of the time.  So
> have_higher_than_11mbit needs to be initialized to false.

LGTM. There's only one caller of ieee80211_get_rates() today; if there
were others, they could make a similar mistake in the future. An
alternate approach: ieee80211_get_rates() could unconditionally write
false before the loop that could later write true. Then call sites
don't need to worry about this conditional assignment. Perhaps that
would be preferable? If not:

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Fixes: 5d6a1b069b7f ("mac80211: set basic rates earlier")
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  net/mac80211/mlme.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
> index 51f55c4ee3c6e..766cbbc9c3a72 100644
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -5279,7 +5279,7 @@ static int ieee80211_prep_connection(struct ieee80211_sub_if_data *sdata,
>          */
>         if (new_sta) {
>                 u32 rates = 0, basic_rates = 0;
> -               bool have_higher_than_11mbit;
> +               bool have_higher_than_11mbit = false;
>                 int min_rate = INT_MAX, min_rate_index = -1;
>                 const struct cfg80211_bss_ies *ies;
>                 int shift = ieee80211_vif_get_shift(&sdata->vif);
> --
> 2.26.3
>


-- 
Thanks,
~Nick Desaulniers