linux-kernel - Re: [PATCH v2 04/16] b43: Remove uninitialized

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Message-ID: <CAKwvOdmsXuqx-3Rt_KNFq4psAeFjG2-7qQaqkJ7dDqqmscUFNw@mail.gmail.com>
Date:   Mon, 22 Jun 2020 10:04:18 -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 Doc Mailing List <linux-doc@...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 v2 04/16] b43: Remove uninitialized_var() usage

On Fri, Jun 19, 2020 at 8:30 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.
> No later NULL deref is possible due to the early returns outside of the
> (phy->rev >= 7 && phy->rev < 19) case, which explicitly tests for NULL.
>
> [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/
>
> Fixes: 58619b14d106 ("b43: move under broadcom vendor directory")
> Signed-off-by: Kees Cook <keescook@...omium.org>

I see three total uses of uninitialized_var() in this file, do we want
to eliminate all of them?

> ---
>  drivers/net/wireless/broadcom/b43/phy_n.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/broadcom/b43/phy_n.c b/drivers/net/wireless/broadcom/b43/phy_n.c
> index c33b4235839d..46db91846007 100644
> --- a/drivers/net/wireless/broadcom/b43/phy_n.c
> +++ b/drivers/net/wireless/broadcom/b43/phy_n.c
> @@ -4222,7 +4222,7 @@ static void b43_nphy_tx_gain_table_upload(struct b43_wldev *dev)
>         u32 rfpwr_offset;
>         u8 pga_gain, pad_gain;
>         int i;
> -       const s16 *uninitialized_var(rf_pwr_offset_table);
> +       const s16 *rf_pwr_offset_table = NULL;
>
>         table = b43_nphy_get_tx_gain_table(dev);
>         if (!table)
> --

-- 
Thanks,
~Nick Desaulniers