Merge branch 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 kaslr update from Ingo Molnar:
 "This adds kernel module load address randomization"

* 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, kaslr: fix module lock ordering problem
  x86, kaslr: randomize module base load address

2 files changed, 45 insertions, 5 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 06600cc9a26c..67755ea834a7 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2060,8 +2060,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         IOAPICs that may be present in the system.
 
         nokaslr         [X86]
-                        Disable kernel base offset ASLR (Address Space
-                        Layout Randomization) if built into the kernel.
+                        Disable kernel and module base offset ASLR (Address
+                        Space Layout Randomization) if built into the kernel.
 
         noautogroup     Disable scheduler automatic task group creation.
 
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 18be189368bb..e69f9882bf95 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -28,6 +28,7 @@
 #include <linux/mm.h>
 #include <linux/gfp.h>
 #include <linux/jump_label.h>
+#include <linux/random.h>
 
 #include <asm/page.h>
 #include <asm/pgtable.h>
@@ -43,13 +44,52 @@ do {							\
 } while (0)
 #endif
 
+#ifdef CONFIG_RANDOMIZE_BASE
+static unsigned long module_load_offset;
+static int randomize_modules = 1;
+
+/* Mutex protects the module_load_offset. */
+static DEFINE_MUTEX(module_kaslr_mutex);
+
+static int __init parse_nokaslr(char *p)
+{
+        randomize_modules = 0;
+        return 0;
+}
+early_param("nokaslr", parse_nokaslr);
+
+static unsigned long int get_module_load_offset(void)
+{
+        if (randomize_modules) {
+                mutex_lock(&module_kaslr_mutex);
+                /*
+                 * Calculate the module_load_offset the first time this
+                 * code is called. Once calculated it stays the same until
+                 * reboot.
+                 */
+                if (module_load_offset == 0)
+                        module_load_offset =
+                                (get_random_int() % 1024 + 1) * PAGE_SIZE;
+                mutex_unlock(&module_kaslr_mutex);
+        }
+        return module_load_offset;
+}
+#else
+static unsigned long int get_module_load_offset(void)
+{
+        return 0;
+}
+#endif
+
 void *module_alloc(unsigned long size)
 {
         if (PAGE_ALIGN(size) > MODULES_LEN)
                 return NULL;
-        return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
-                                GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
-                                NUMA_NO_NODE, __builtin_return_address(0));
+        return __vmalloc_node_range(size, 1,
+                                    MODULES_VADDR + get_module_load_offset(),
+                                    MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
+                                    PAGE_KERNEL_EXEC, NUMA_NO_NODE,
+                                    __builtin_return_address(0));
 }
 
 #ifdef CONFIG_X86_32