linux-kernel - Re: [PATCH 03/20] reboot: Remove the unreachable panic after do

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Message-ID: <202110210903.64145A81@keescook>
Date:   Thu, 21 Oct 2021 09:05:03 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 03/20] reboot: Remove the unreachable panic after do_exit
 in reboot(2)

On Wed, Oct 20, 2021 at 12:43:49PM -0500, Eric W. Biederman wrote:
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> ---
>  kernel/reboot.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/kernel/reboot.c b/kernel/reboot.c
> index f7440c0c7e43..d6e0f9fb7f04 100644
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -359,7 +359,6 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
>  	case LINUX_REBOOT_CMD_HALT:
>  		kernel_halt();
>  		do_exit(0);
> -		panic("cannot halt");

This looks like it was here for robustness (i.e. panic if do_exit
somehow fails)? But since do_exit() is marked __no_return, it doesn't
make sense to keep it. If we wanted to keep _something_ here, maybe just
add unreachable() ?

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

>  
>  	case LINUX_REBOOT_CMD_POWER_OFF:
>  		kernel_power_off();
> -- 
> 2.20.1
> 

-- 
Kees Cook