linux-kernel - Re: [PATCH 02/10] drbd: Remove uninitialized

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Message-ID: <CAKwvOdmfOSGAZiuapXOaiU74AQVMDgimrnCiRDjzw4p4oh1vaw@mail.gmail.com>
Date:   Thu, 4 Jun 2020 12:56:11 -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 02/10] drbd: 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.
>
> [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: a29728463b25 ("drbd: Backport the "events2" command")

> ---
>  drivers/block/drbd/drbd_state.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
> index eeaa3b49b264..0067d328f0b5 100644
> --- a/drivers/block/drbd/drbd_state.c
> +++ b/drivers/block/drbd/drbd_state.c
> @@ -1604,7 +1604,7 @@ static void broadcast_state_change(struct drbd_state_change *state_change)
>         unsigned int n_device, n_connection, n_peer_device, n_peer_devices;
>         void (*last_func)(struct sk_buff *, unsigned int, void *,
>                           enum drbd_notification_type) = NULL;
> -       void *uninitialized_var(last_arg);
> +       void *last_arg = NULL;
>
>  #define HAS_CHANGED(state) ((state)[OLD] != (state)[NEW])
>  #define FINAL_STATE_CHANGE(type) \
> --
> 2.25.1
>
> --
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-- 
Thanks,
~Nick Desaulniers