lkdtm: adjust usercopy tests to bypass const checks

[cascardo/linux.git] / drivers / misc / lkdtm_usercopy.c

diff --git a/drivers/misc/lkdtm_usercopy.c b/drivers/misc/lkdtm_usercopy.c
index 5525a20..1dd6114 100644 (file)
--- a/drivers/misc/lkdtm_usercopy.c
+++ b/drivers/misc/lkdtm_usercopy.c
@@ -9,7 +9,15 @@
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
 
-static size_t cache_size = 1024;
+/*
+ * Many of the tests here end up using const sizes, but those would
+ * normally be ignored by hardened usercopy, so force the compiler
+ * into choosing the non-const path to make sure we trigger the
+ * hardened usercopy checks by added "unconst" to all the const copies,
+ * and making sure "cache_size" isn't optimized into a const.
+ */
+static volatile size_t unconst = 0;
+static volatile size_t cache_size = 1024;
 static struct kmem_cache *bad_cache;
 
 static const unsigned char test_text[] = "This is a test.\n";
@@ -67,14 +75,14 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
        if (to_user) {
                pr_info("attempting good copy_to_user of local stack\n");
                if (copy_to_user((void __user *)user_addr, good_stack,
-                                sizeof(good_stack))) {
+                                unconst + sizeof(good_stack))) {
                        pr_warn("copy_to_user failed unexpectedly?!\n");
                        goto free_user;
                }
 
                pr_info("attempting bad copy_to_user of distant stack\n");
                if (copy_to_user((void __user *)user_addr, bad_stack,
-                                sizeof(good_stack))) {
+                                unconst + sizeof(good_stack))) {
                        pr_warn("copy_to_user failed, but lacked Oops\n");
                        goto free_user;
                }
@@ -88,14 +96,14 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame)
 
                pr_info("attempting good copy_from_user of local stack\n");
                if (copy_from_user(good_stack, (void __user *)user_addr,
-                                  sizeof(good_stack))) {
+                                  unconst + sizeof(good_stack))) {
                        pr_warn("copy_from_user failed unexpectedly?!\n");
                        goto free_user;
                }
 
                pr_info("attempting bad copy_from_user of distant stack\n");
                if (copy_from_user(bad_stack, (void __user *)user_addr,
-                                  sizeof(good_stack))) {
+                                  unconst + sizeof(good_stack))) {
                        pr_warn("copy_from_user failed, but lacked Oops\n");
                        goto free_user;
                }
@@ -109,7 +117,7 @@ static void do_usercopy_heap_size(bool to_user)
 {
        unsigned long user_addr;
        unsigned char *one, *two;
-       const size_t size = 1024;
+       size_t size = unconst + 1024;
 
        one = kmalloc(size, GFP_KERNEL);
        two = kmalloc(size, GFP_KERNEL);
@@ -285,13 +293,14 @@ void lkdtm_USERCOPY_KERNEL(void)
 
        pr_info("attempting good copy_to_user from kernel rodata\n");
        if (copy_to_user((void __user *)user_addr, test_text,
-                        sizeof(test_text))) {
+                        unconst + sizeof(test_text))) {
                pr_warn("copy_to_user failed unexpectedly?!\n");
                goto free_user;
        }
 
        pr_info("attempting bad copy_to_user from kernel text\n");
-       if (copy_to_user((void __user *)user_addr, vm_mmap, PAGE_SIZE)) {
+       if (copy_to_user((void __user *)user_addr, vm_mmap,
+                        unconst + PAGE_SIZE)) {
                pr_warn("copy_to_user failed, but lacked Oops\n");
                goto free_user;
        }