Re: [PATCH V35 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down
From: Dave Young <hidden>
Date: 2019-07-16 02:59:36
Also in:
linux-acpi, linux-security-module, lkml
Hi, On 07/15/19 at 12:59pm, Matthew Garrett wrote:
quoted hunk ↗ jump to hunk
From: Josh Boyer <redacted> This option allows userspace to pass the RSDP address to the kernel, which makes it possible for a user to modify the workings of hardware . Reject the option when the kernel is locked down. Signed-off-by: Josh Boyer <redacted> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <redacted> Reviewed-by: Kees Cook <redacted> cc: Dave Young <redacted> cc: linux-acpi@vger.kernel.org --- drivers/acpi/osl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index 9c0edf2fc0dd..06e7cffc4386 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c@@ -26,6 +26,7 @@ #include <linux/list.h> #include <linux/jiffies.h> #include <linux/semaphore.h> +#include <linux/security.h> #include <asm/io.h> #include <linux/uaccess.h>@@ -180,7 +181,7 @@ acpi_physical_address __init acpi_os_get_root_pointer(void) acpi_physical_address pa; #ifdef CONFIG_KEXEC - if (acpi_rsdp) + if (acpi_rsdp && !security_locked_down(LOCKDOWN_ACPI_TABLES)) return acpi_rsdp;
I'm very sorry I noticed this late, but have to say this will not work for
X86 with latest kernel code.
acpi_physical_address __init acpi_os_get_root_pointer(void)
{
acpi_physical_address pa;
#ifdef CONFIG_KEXEC
if (acpi_rsdp)
return acpi_rsdp;
#endif
pa = acpi_arch_get_root_pointer();
if (pa)
return pa;
[snip]
In above code, the later acpi_arch_get_root_pointer still get acpi_rsdp
from cmdline param if provided.
You can check the arch/x86/boot/compressed/acpi.c, and
arch/x86/kernel/acpi/boot.c
In X86 early code, cmdline provided acpi_rsdp pointer will be saved in boot_params.acpi_rsdp_addr;
and the used in x86_default_get_root_pointer
#endif pa = acpi_arch_get_root_pointer(); -- 2.22.0.510.g264f2c817a-goog
Thanks Dave