ACPI: Add access checking (Andi Kleen)

drivers/acpi/osl.c

@@ -38,6 +38,7 @@
 #include <acpi/acpi.h>
 #include <asm/io.h>
 #include <acpi/acpi_bus.h>
+#include <asm/uaccess.h>
 
 #ifdef CONFIG_ACPI_EFI
 #include <linux/efi.h>
@@ -948,19 +949,22 @@ acpi_os_get_line(char *buffer)
 	return 0;
 }
 
-/*
- * We just have to assume we're dealing with valid memory
- */
-
+/* Assumes no unreadable holes inbetween */
 BOOLEAN
 acpi_os_readable(void *ptr, u32 len)
 {
+#if defined(__i386__) || defined(__x86_64__) 
+	char tmp;
+	return !__get_user(tmp, (char *)ptr) && !__get_user(tmp, (char *)ptr + len - 1);
+#endif
 	return 1;
 }
 
 BOOLEAN
 acpi_os_writable(void *ptr, u32 len)
 {
+	/* could do dummy write (racy) or a kernel page table lookup.
+	   The later may be difficult at early boot when kmap doesn't work yet. */
 	return 1;
 }