linux-kernel - Re: [PATCH v3] kdb: remove unnecessary null check of dbg_io

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Message-ID: <CAFA6WYPDTKQ4cm+TMmRt+qDiF+s3gggCsW1gfzCaaOdP9rJgdQ@mail.gmail.com>
Date:   Tue, 30 Jun 2020 17:06:31 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Cengiz Can <cengiz@...nel.wtf>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        kgdb-bugreport@...ts.sourceforge.net,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH v3] kdb: remove unnecessary null check of dbg_io_ops

On Tue, 30 Jun 2020 at 14:00, Cengiz Can <cengiz@...nel.wtf> wrote:
>
> `kdb_msg_write` operates on a global `struct kgdb_io *` called
> `dbg_io_ops`.
>
> It's initialized in `debug_core.c` and checked throughout the debug
> flow.
>
> There's a null check in `kdb_msg_write` which triggers static analyzers
> and gives the (almost entirely wrong) impression that it can be null.
>
> Coverity scanner caught this as CID 1465042.
>
> I have removed the unnecessary null check and eliminated false-positive
> forward null dereference warning.
>
> Signed-off-by: Cengiz Can <cengiz@...nel.wtf>
> ---
>  kernel/debug/kdb/kdb_io.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>

Reviewed-by: Sumit Garg <sumit.garg@...aro.org>

> diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
> index 683a799618ad..81783ecaec58 100644
> --- a/kernel/debug/kdb/kdb_io.c
> +++ b/kernel/debug/kdb/kdb_io.c
> @@ -545,18 +545,18 @@ static int kdb_search_string(char *searched, char *searchfor)
>  static void kdb_msg_write(const char *msg, int msg_len)
>  {
>         struct console *c;
> +       const char *cp;
> +       int len;
>
>         if (msg_len == 0)
>                 return;
>
> -       if (dbg_io_ops) {
> -               const char *cp = msg;
> -               int len = msg_len;
> +       cp = msg;
> +       len = msg_len;
>
> -               while (len--) {
> -                       dbg_io_ops->write_char(*cp);
> -                       cp++;
> -               }
> +       while (len--) {
> +               dbg_io_ops->write_char(*cp);
> +               cp++;
>         }
>
>         for_each_console(c) {
> --
> 2.27.0
>