linux-kernel - Re: [PATCH 04/10] rtlwifi: rtl8192cu: Remove uninitialized

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Date:   Thu, 4 Jun 2020 13:16:08 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Joe Perches <joe@...ches.com>,
        Andy Whitcroft <apw@...onical.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        drbd-dev@...ts.linbit.com, linux-block@...r.kernel.org,
        b43-dev@...ts.infradead.org,
        Network Development <netdev@...r.kernel.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        linux-ide@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-spi@...r.kernel.org,
        Linux Memory Management List <linux-mm@...ck.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH 04/10] rtlwifi: rtl8192cu: Remove uninitialized_var() usage

On Wed, Jun 3, 2020 at 4:32 PM Kees Cook <keescook@...omium.org> wrote:
>
> Using uninitialized_var() is dangerous as it papers over real bugs[1]
> (or can in the future), and suppresses unrelated compiler warnings (e.g.
> "unused variable"). If the compiler thinks it is uninitialized, either
> simply initialize the variable or make compiler changes. As a precursor
> to removing[2] this[3] macro[4], just initialize this variable to NULL,
> and avoid sending garbage by returning.
>
> [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
> [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
> [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
> [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Fixes: dc0313f46664 ("rtlwifi: rtl8192cu: Add routine hw")

> ---
>  drivers/net/wireless/realtek/rtlwifi/rtl8192cu/hw.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8192cu/hw.c b/drivers/net/wireless/realtek/rtlwifi/rtl8192cu/hw.c
> index f070f25bb735..5b071b70bc08 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8192cu/hw.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8192cu/hw.c
> @@ -592,7 +592,7 @@ static void _rtl92cu_init_chipn_one_out_ep_priority(struct ieee80211_hw *hw,
>                                                     bool wmm_enable,
>                                                     u8 queue_sel)
>  {
> -       u16 uninitialized_var(value);
> +       u16 value;
>
>         switch (queue_sel) {
>         case TX_SELE_HQ:
> @@ -606,7 +606,7 @@ static void _rtl92cu_init_chipn_one_out_ep_priority(struct ieee80211_hw *hw,
>                 break;
>         default:
>                 WARN_ON(1); /* Shall not reach here! */
> -               break;
> +               return;
>         }
>         _rtl92c_init_chipn_reg_priority(hw, value, value, value, value,
>                                         value, value);

Whew! Nothing like passing the same value 6 times! (Other callers do
use distinct values though, just curious seeing this instance.)

-- 
Thanks,
~Nick Desaulniers