[PATCH] x86/acpi: check rsdp address received via bootparams to be valid

[Juergen Gross <jgross@suse.com>]

There seem to exist several grub2 versions trashing
boot_params.hdr.acpi_rsdp_addr.

So don't just believe this address to be valid, but verify it pointing
to a valid RSDP table.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
To be applied on top of my RSDP series currently in tip.git x86/boot
Mike Galbraith has tested this patch to repair his broken boot
---
 drivers/acpi/acpica/tbxfroot.c | 36 ++++++++++++++++++++++++++++++++++++
 drivers/acpi/osl.c             |  2 +-
 include/acpi/acpixf.h          |  5 +++++
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpica/tbxfroot.c b/drivers/acpi/acpica/tbxfroot.c
index f9f9a7da2cad..9edc71780a38 100644
--- a/drivers/acpi/acpica/tbxfroot.c
+++ b/drivers/acpi/acpica/tbxfroot.c
@@ -249,6 +249,42 @@ ACPI_EXPORT_SYMBOL_INIT(acpi_find_root_pointer)
 
 /*******************************************************************************
  *
+ * FUNCTION:    acpi_verify_root_pointer
+ *
+ *
+ * PARAMETERS:  rsdp_address        - Pointer to suspected RSDP
+ *
+ * RETURN:      AE_OK if rsdp_address really points to a RSDP, AE_NOT_FOUND
+ *              else
+ *
+ * DESCRIPTION: Verify a physical address being a valid RSDP
+ *
+ ******************************************************************************/
+
+acpi_status ACPI_INIT_FUNCTION
+acpi_verify_root_pointer(acpi_physical_address rsdp_address)
+{
+	acpi_status status;
+	struct acpi_table_rsdp *rsdp;
+
+	ACPI_FUNCTION_TRACE(acpi_verify_root_pointer);
+
+	rsdp = acpi_os_map_memory(rsdp_address, sizeof(*rsdp));
+
+	if (!rsdp)
+		return_ACPI_STATUS(AE_NO_MEMORY);
+
+	status = acpi_tb_validate_rsdp(rsdp);
+
+	acpi_os_unmap_memory(rsdp, sizeof(*rsdp));
+
+	return_ACPI_STATUS(status);
+}
+
+ACPI_EXPORT_SYMBOL_INIT(acpi_verify_root_pointer)
+
+/*******************************************************************************
+ *
  * FUNCTION:    acpi_tb_scan_memory_for_rsdp
  *
  * PARAMETERS:  start_address       - Starting pointer for search
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 2b77db914752..facff5c11f32 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -201,7 +201,7 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
 		return acpi_rsdp;
 #endif
 	pa = acpi_arch_get_root_pointer();
-	if (pa)
+	if (pa && acpi_verify_root_pointer(pa) == AE_OK)
 		return pa;
 
 	if (efi_enabled(EFI_CONFIG_TABLES)) {
diff --git a/include/acpi/acpixf.h b/include/acpi/acpixf.h
index e1dd1a8d42b6..1edc47bd13c1 100644
--- a/include/acpi/acpixf.h
+++ b/include/acpi/acpixf.h
@@ -505,6 +505,11 @@ ACPI_EXTERNAL_RETURN_STATUS(acpi_status ACPI_INIT_FUNCTION
 ACPI_EXTERNAL_RETURN_STATUS(acpi_status ACPI_INIT_FUNCTION
 			    acpi_find_root_pointer(acpi_physical_address
 						   *rsdp_address))
+
+ACPI_EXTERNAL_RETURN_OK(acpi_status ACPI_INIT_FUNCTION
+			acpi_verify_root_pointer(acpi_physical_address
+						 rsdp_address))
+
 ACPI_EXTERNAL_RETURN_STATUS(acpi_status
 			     acpi_get_table_header(acpi_string signature,
 						   u32 instance,
-- 
2.13.6