linux-kernel - Re: [PATCH v5] kconfig: avoid an infinite loop in oldconfig/syncconfig

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Message-ID: <CAK7LNAS6J5Nh8nOUHbaf123yd1Z-1q--FvB1ok8GQcoNorAROw@mail.gmail.com>
Date:   Sun, 5 Nov 2023 16:55:57 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Yoann Congal <yoann.congal@...le.fr>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Randy Dunlap <rdunlap@...radead.org>,
        Brandon Maier <brandon.maier@...lins.com>
Subject: Re: [PATCH v5] kconfig: avoid an infinite loop in oldconfig/syncconfig

On Sun, Nov 5, 2023 at 7:27 AM Yoann Congal <yoann.congal@...le.fr> wrote:
>
> Exit on error when asking for value and reading stdin returns an error
> (mainly if it has reached EOF or is closed).
>
> This infinite loop happens in particular for hex/int configs without an
> explicit default value.
>
> Previously, this case would loop:
> * oldconfig prompts for the value but stdin has reached EOF
> * It gets the global default value : an empty string
> * This is not a valid hex/int value so it prompts again, hence the
>   infinite loop.
>
> This case happens with a configuration like this (a hex config without a
> valid default value):
>   config TEST_KCONFIG
>        hex "Test KConfig"
>        # default 0x0
>
> And using:
>   make oldconfig < /dev/null
>
> This was discovered when working on Yocto bug[0] on a downstream
> kconfig user (U-boot)
>
> [0]: https://bugzilla.yoctoproject.org/show_bug.cgi?id=14136
>
> CC: Brandon Maier <brandon.maier@...lins.com>
> Signed-off-by: Yoann Congal <yoann.congal@...le.fr>

Applied to linux-kbuild.
Thanks.


> ---
> v4->v5:
>  * Switched to Masahiro Yamada's suggested code.
> v3->v4:
>  * Added Brandon Maier's "Tested-by". Thanks!
> v2->v3:
>  * Simplify the patch by fusing comments of :
>    * Masahiro Yamada : Exit as soon as reading stdin hits an error
>    * Randy Dunlap : Display the name of the currently read symbol
> v1->v2:
>  * Improve coding style
>  * Put more info in the commit message
> ---
>  scripts/kconfig/conf.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
> index 33d19e419908..62de1fbaff97 100644
> --- a/scripts/kconfig/conf.c
> +++ b/scripts/kconfig/conf.c
> @@ -76,8 +76,10 @@ static void strip(char *str)
>  /* Helper function to facilitate fgets() by Jean Sacren. */
>  static void xfgets(char *str, int size, FILE *in)
>  {
> -       if (!fgets(str, size, in))
> +       if (!fgets(str, size, in)) {
>                 fprintf(stderr, "\nError in reading or end of file.\n");
> +               exit(1);
> +       }
>
>         if (!tty_stdio)
>                 printf("%s", str);
> --
> 2.30.2
>


-- 
Best Regards
Masahiro Yamada