Messages in this thread | | | Date | Tue, 16 Jul 2019 10:59:23 +0800 | From | Dave Young <> | Subject | Re: [PATCH V35 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down |
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Hi, On 07/15/19 at 12:59pm, Matthew Garrett wrote: > From: Josh Boyer <jwboyer@redhat.com> > > 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 <jwboyer@redhat.com> > Signed-off-by: David Howells <dhowells@redhat.com> > Signed-off-by: Matthew Garrett <mjg59@google.com> > Reviewed-by: Kees Cook <keescook@chromium.org> > cc: Dave Young <dyoung@redhat.com> > 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
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