linux-kernel - Re: [PATCH] Make initramfs honor CONFIG_DEVTMPFS

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Date:   Thu, 4 May 2017 16:34:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Rob Landley <rob@...dley.net>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Prarit Bhargava <prarit@...hat.com>,
        Yang Shi <yang.shi@...aro.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Emese Revfy <re.emese@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Fabian Frederick <fabf@...net.be>
Subject: Re: [PATCH] Make initramfs honor CONFIG_DEVTMPFS_MOUNT

On Thu, May 4, 2017 at 2:09 PM, Rob Landley <rob@...dley.net> wrote:
> From: Rob Landley <rob@...dley.net>
>
> Make initramfs honor CONFIG_DEVTMPFS_MOUNT, and move
> /dev/console open after devtmpfs mount.
>
> Signed-off-by: Rob Landley <rob@...dley.net>

Seems sensible.

Reviewed-by: Kees Cook <keescook@...omium.org>


-Kees

> ---
>
>  init/main.c |   15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/init/main.c b/init/main.c
> index 2858be7..71ed0d7 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1016,12 +1016,6 @@ static noinline void __init kernel_init_freeable(void)
>
>         do_basic_setup();
>
> -       /* Open the /dev/console on the rootfs, this should never fail */
> -       if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
> -               pr_err("Warning: unable to open an initial console.\n");
> -
> -       (void) sys_dup(0);
> -       (void) sys_dup(0);
>         /*
>          * check if there is an early userspace init.  If yes, let it do all
>          * the work
> @@ -1033,8 +1027,17 @@ static noinline void __init kernel_init_freeable(void)
>         if (sys_access((const char __user *) ramdisk_execute_command, 0) != 0) {
>                 ramdisk_execute_command = NULL;
>                 prepare_namespace();
> +       } else if (IS_ENABLED(CONFIG_DEVTMPFS_MOUNT)) {
> +               sys_mkdir("/dev", 0755);
> +               sys_mount("dev", "dev", "devtmpfs", MS_SILENT, NULL);
>         }
>
> +       /* Open the /dev/console on the rootfs, this should never fail */
> +       if (sys_open((const char __user *) "/dev/console", O_RDWR, 0) < 0)
> +               pr_err("Warning: unable to open an initial console.\n");
> +       (void) sys_dup(0);
> +       (void) sys_dup(0);
> +
>         /*
>          * Ok, we have completed the initial bootup, and
>          * we're essentially up and running. Get rid of the



-- 
Kees Cook
Pixel Security