7 files changed, 49 insertions, 7 deletions

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index ad84239e595e..e726e9b44bb1 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -26,7 +26,7 @@ struct mem_vector immovable_mem[MAX_NUMNODES*2];
  */
 #define MAX_ADDR_LEN 19
 
-static acpi_physical_address get_acpi_rsdp(void)
+static acpi_physical_address get_cmdline_acpi_rsdp(void)
 {
         acpi_physical_address addr = 0;
 
@@ -215,10 +215,7 @@ acpi_physical_address get_rsdp_addr(void)
 {
         acpi_physical_address pa;
 
-        pa = get_acpi_rsdp();
-
-        if (!pa)
-                pa = boot_params->acpi_rsdp_addr;
+        pa = boot_params->acpi_rsdp_addr;
 
         if (!pa)
                 pa = efi_get_rsdp_addr();
@@ -240,7 +237,17 @@ static unsigned long get_acpi_srat_table(void)
         char arg[10];
         u8 *entry;
 
-        rsdp = (struct acpi_table_rsdp *)(long)boot_params->acpi_rsdp_addr;
+        /*
+         * Check whether we were given an RSDP on the command line. We don't
+         * stash this in boot params because the kernel itself may have
+         * different ideas about whether to trust a command-line parameter.
+         */
+        rsdp = (struct acpi_table_rsdp *)get_cmdline_acpi_rsdp();
+
+        if (!rsdp)
+                rsdp = (struct acpi_table_rsdp *)(long)
+                        boot_params->acpi_rsdp_addr;
+
         if (!rsdp)
                 return 0;
 
diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
index aac686e1e005..bc9693c9107e 100644
--- a/arch/x86/include/asm/acpi.h
+++ b/arch/x86/include/asm/acpi.h
@@ -117,6 +117,12 @@ static inline bool acpi_has_cpu_in_madt(void)
         return !!acpi_lapic;
 }
 
+#define ACPI_HAVE_ARCH_SET_ROOT_POINTER
+static inline void acpi_arch_set_root_pointer(u64 addr)
+{
+        x86_init.acpi.set_root_pointer(addr);
+}
+
 #define ACPI_HAVE_ARCH_GET_ROOT_POINTER
 static inline u64 acpi_arch_get_root_pointer(void)
 {
@@ -125,6 +131,7 @@ static inline u64 acpi_arch_get_root_pointer(void)
 
 void acpi_generic_reduced_hw_init(void);
 
+void x86_default_set_root_pointer(u64 addr);
 u64 x86_default_get_root_pointer(void);
 
 #else /* !CONFIG_ACPI */
@@ -138,6 +145,8 @@ static inline void disable_acpi(void) { }
 
 static inline void acpi_generic_reduced_hw_init(void) { }
 
+static inline void x86_default_set_root_pointer(u64 addr) { }
+
 static inline u64 x86_default_get_root_pointer(void)
 {
         return 0;
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index b85a7c54c6a1..d584128435cb 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -134,10 +134,12 @@ struct x86_hyper_init {
 
 /**
  * struct x86_init_acpi - x86 ACPI init functions
+ * @set_root_poitner:           set RSDP address
  * @get_root_pointer:           get RSDP address
  * @reduced_hw_early_init:      hardware reduced platform early init
  */
 struct x86_init_acpi {
+        void (*set_root_pointer)(u64 addr);
         u64 (*get_root_pointer)(void);
         void (*reduced_hw_early_init)(void);
 };
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 17b33ef604f3..04205ce127a1 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1760,6 +1760,11 @@ void __init arch_reserve_mem_area(acpi_physical_address addr, size_t size)
         e820__update_table_print();
 }
 
+void x86_default_set_root_pointer(u64 addr)
+{
+        boot_params.acpi_rsdp_addr = addr;
+}
+
 u64 x86_default_get_root_pointer(void)
 {
         return boot_params.acpi_rsdp_addr;
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index 50a2b492fdd6..d0b8f5585a73 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -95,6 +95,7 @@ struct x86_init_ops x86_init __initdata = {
         },
 
         .acpi = {
+                .set_root_pointer       = x86_default_set_root_pointer,
                 .get_root_pointer       = x86_default_get_root_pointer,
                 .reduced_hw_early_init  = acpi_generic_reduced_hw_init,
         },
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index cc7507091dec..b7c3aeb175dd 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>
@@ -180,8 +181,19 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
         acpi_physical_address pa;
 
 #ifdef CONFIG_KEXEC
-        if (acpi_rsdp)
+        /*
+         * We may have been provided with an RSDP on the command line,
+         * but if a malicious user has done so they may be pointing us
+         * at modified ACPI tables that could alter kernel behaviour -
+         * so, we check the lockdown status before making use of
+         * it. If we trust it then also stash it in an architecture
+         * specific location (if appropriate) so it can be carried
+         * over further kexec()s.
+         */
+        if (acpi_rsdp && !security_locked_down(LOCKDOWN_ACPI_TABLES)) {
+                acpi_arch_set_root_pointer(acpi_rsdp);
                 return acpi_rsdp;
+        }
 #endif
         pa = acpi_arch_get_root_pointer();
         if (pa)
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index d315d86844e4..268a4d91f54c 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -632,6 +632,12 @@ bool acpi_gtdt_c3stop(int type);
 int acpi_arch_timer_mem_init(struct arch_timer_mem *timer_mem, int *timer_count);
 #endif
 
+#ifndef ACPI_HAVE_ARCH_SET_ROOT_POINTER
+static inline void acpi_arch_set_root_pointer(u64 addr)
+{
+}
+#endif
+
 #ifndef ACPI_HAVE_ARCH_GET_ROOT_POINTER
 static inline u64 acpi_arch_get_root_pointer(void)
 {