linux-kernel - Re: [PATCH 07/24] kexec: Disable at runtime if the kernel is locked down

Open Source and information security mailing list archives

Date:   Fri, 7 Apr 2017 11:07:05 +0800
From:   Dave Young <dyoung@...hat.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-kernel@...r.kernel.org, matthew.garrett@...ula.com,
        linux-efi@...r.kernel.org, gnomes@...rguk.ukuu.org.uk,
        gregkh@...uxfoundation.org, kexec@...ts.infradead.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH 07/24] kexec: Disable at runtime if the kernel is locked
 down

On 04/05/17 at 09:15pm, David Howells wrote:
> From: Matthew Garrett <matthew.garrett@...ula.com>
> 
> kexec permits the loading and execution of arbitrary code in ring 0, which
> is something that lock-down is meant to prevent. It makes sense to disable
> kexec in this situation.
> 
> This does not affect kexec_file_load() which can check for a signature on the
> image to be booted.
> 
> Signed-off-by: Matthew Garrett <matthew.garrett@...ula.com>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: kexec@...ts.infradead.org
> ---
> 
>  kernel/kexec.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index 980936a90ee6..46de8e6b42f4 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -194,6 +194,13 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
>  		return -EPERM;
>  
>  	/*
> +	 * kexec can be used to circumvent module loading restrictions, so
> +	 * prevent loading in that case
> +	 */
> +	if (kernel_is_locked_down())
> +		return -EPERM;
> +
> +	/*
>  	 * Verify we have a legal set of flags
>  	 * This leaves us room for future extensions.
>  	 */
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Acked-by: Dave Young <dyoung@...hat.com>

Thanks
Dave

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