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From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: Matthew Garrett <mjg@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org, linux-efi@vger.kernel.org
Subject: Re: [PATCH 07/11] kexec: Disable in a secure boot environment
Date: Wed, 05 Sep 2012 17:13:49 -0400	[thread overview]
Message-ID: <1346879629.2054.22.camel@falcor.watson.ibm.com> (raw)
In-Reply-To: <1346774117-2277-8-git-send-email-mjg@redhat.com>

On Tue, 2012-09-04 at 11:55 -0400, Matthew Garrett wrote:
> kexec could be used as a vector for a malicious user to use a signed kernel
> to circumvent the secure boot trust model. In the long run we'll want to
> support signed kexec payloads, but for the moment we should just disable
> loading entirely in that situation.
> 
> Signed-off-by: Matthew Garrett <mjg@redhat.com>
> ---
>  kernel/kexec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index 0668d58..48852ec 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -944,7 +944,7 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
>  	int result;
> 
>  	/* We only trust the superuser with rebooting the system. */
> -	if (!capable(CAP_SYS_BOOT))
> +	if (!capable(CAP_SYS_BOOT) || !capable(CAP_SECURE_FIRMWARE))
>  		return -EPERM;
> 
>  	/*

Normally capabilities provide additional permissions. So if you don't
have the capability, an errno is returned.  CAP_SYS_BOOT is a good
example.  With CAP_SECURE_FIRMWARE, it reads backwards - if not
CAP_SECURE_FIRMWARE, return error.  I think you want to invert the name
to CAP_NOT_SECURE_FIRMWARE, CAP_NOT_SECURE_BOOT or perhaps
CAP_UNSECURED_BOOT.

Mimi


  parent reply	other threads:[~2012-09-05 21:16 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-04 15:55 [RFC] First attempt at kernel secure boot support Matthew Garrett
2012-09-04 15:55 ` [PATCH 01/11] Secure boot: Add new capability Matthew Garrett
2012-09-04 15:55 ` [PATCH 02/11] PCI: Lock down BAR access in secure boot environments Matthew Garrett
2012-10-01 21:00   ` Pavel Machek
2012-09-04 15:55 ` [PATCH 03/11] x86: Lock down IO port " Matthew Garrett
2012-09-04 16:16   ` Alan Cox
2012-09-04 16:16     ` Matthew Garrett
2012-09-04 15:55 ` [PATCH 04/11] ACPI: Limit access to custom_method Matthew Garrett
2012-09-04 15:55 ` [PATCH 05/11] asus-wmi: Restrict debugfs interface Matthew Garrett
2012-09-04 16:12   ` Alan Cox
2012-09-04 16:13     ` Matthew Garrett
2012-09-04 15:55 ` [PATCH 06/11] Restrict /dev/mem and /dev/kmem in secure boot setups Matthew Garrett
2012-09-04 15:55 ` [PATCH 07/11] kexec: Disable in a secure boot environment Matthew Garrett
2012-09-04 20:13   ` Eric W. Biederman
2012-09-04 20:22     ` Matthew Garrett
2012-09-04 21:13       ` Eric W. Biederman
2012-09-04 21:27         ` Matthew Garrett
2012-09-04 22:12           ` Eric W. Biederman
2012-09-04 23:25             ` Matthew Garrett
2012-09-05  4:33               ` Eric W. Biederman
2012-09-05  5:16                 ` Matthew Garrett
2012-09-05  7:00                   ` Eric W. Biederman
2012-09-05  7:03                     ` Matthew Garrett
2012-09-04 21:39         ` Alan Cox
2012-09-04 21:40           ` Matthew Garrett
2012-09-05 15:43             ` Roland Eggner
2012-09-05 15:46               ` Matthew Garrett
2012-09-05 21:13   ` Mimi Zohar [this message]
2012-09-05 21:41     ` Matthew Garrett
2012-09-05 21:49       ` Eric Paris
2012-09-04 15:55 ` [PATCH 08/11] Secure boot: Add a dummy kernel parameter that will switch on Secure Boot mode Matthew Garrett
2012-09-04 15:55 ` [PATCH 09/11] efi: Enable secure boot lockdown automatically when enabled in firmware Matthew Garrett
2012-09-04 15:55 ` [PATCH 10/11] acpi: Ignore acpi_rsdp kernel parameter in a secure boot environment Matthew Garrett
2012-09-04 16:30   ` Shuah Khan
2012-09-04 16:38     ` Matthew Garrett
2012-09-04 16:44       ` Shuah Khan
2012-09-04 20:37         ` Alan Cox
2012-09-04 20:37           ` Matthew Garrett
2012-09-04 20:50             ` Josh Boyer
2012-09-04 15:55 ` [PATCH 11/11] SELinux: define mapping for new Secure Boot capability Matthew Garrett
2012-09-04 16:08 ` [RFC] First attempt at kernel secure boot support Alan Cox
2012-09-04 16:12   ` Matthew Garrett
2012-10-01 21:07     ` Pavel Machek

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