1 files changed, 104 insertions, 27 deletions

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 2dede2ef658f..e1f5e9abb301 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -9,7 +9,9 @@
 #include <linux/vmalloc.h>
 #include <linux/mman.h>
 #include <linux/uaccess.h>
+#include <linux/objtool.h>
 #include <asm/cacheflush.h>
+#include <asm/sections.h>
 
 /* Whether or not to fill the target memory area with do_nothing(). */
 #define CODE_WRITE	true
@@ -21,65 +23,98 @@
 /* This is non-const, so it will end up in the .data section. */
 static u8 data_area[EXEC_SIZE];
 
-/* This is cost, so it will end up in the .rodata section. */
+/* This is const, so it will end up in the .rodata section. */
 static const unsigned long rodata = 0xAA55AA55;
 
 /* This is marked __ro_after_init, so it should ultimately be .rodata. */
 static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
 
 /*
+ * This is a pointer to do_nothing() which is initialized at runtime rather
+ * than build time to avoid objtool IBT validation warnings caused by an
+ * inlined unrolled memcpy() in execute_location().
+ */
+static void __ro_after_init *do_nothing_ptr;
+
+/*
  * This just returns to the caller. It is designed to be copied into
  * non-executable memory regions.
  */
-static void do_nothing(void)
+static noinline void do_nothing(void)
 {
 	return;
 }
 
 /* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
+static noinline void do_overwritten(void)
 {
 	pr_info("do_overwritten wasn't overwritten!\n");
 	return;
 }
 
-static noinline void execute_location(void *dst, bool write)
+static noinline void do_almost_nothing(void)
+{
+	pr_info("do_nothing was hijacked!\n");
+}
+
+static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
 {
-	void (*func)(void) = dst;
+	if (!have_function_descriptors())
+		return dst;
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	memcpy(fdesc, do_nothing, sizeof(*fdesc));
+	fdesc->addr = (unsigned long)dst;
+	barrier();
+
+	return fdesc;
+}
+
+static noinline __nocfi void execute_location(void *dst, bool write)
+{
+	void (*func)(void);
+	func_desc_t fdesc;
+
+	pr_info("attempting ok execution at %px\n", do_nothing_ptr);
 	do_nothing();
 
 	if (write == CODE_WRITE) {
-		memcpy(dst, do_nothing, EXEC_SIZE);
+		memcpy(dst, do_nothing_ptr, EXEC_SIZE);
 		flush_icache_range((unsigned long)dst,
 				   (unsigned long)dst + EXEC_SIZE);
 	}
-	pr_info("attempting bad execution at %px\n", func);
+	pr_info("attempting bad execution at %px\n", dst);
+	func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
+/*
+ * Explicitly doing the wrong thing for testing.
+ */
+ANNOTATE_NOCFI_SYM(execute_location);
 
 static void execute_user_location(void *dst)
 {
 	int copied;
 
 	/* Intentionally crossing kernel/user memory boundary. */
-	void (*func)(void) = dst;
+	void (*func)(void);
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
-	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
+	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
 				   EXEC_SIZE, FOLL_WRITE);
 	if (copied < EXEC_SIZE)
 		return;
-	pr_info("attempting bad execution at %px\n", func);
+	pr_info("attempting bad execution at %px\n", dst);
+	func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
 
-void lkdtm_WRITE_RO(void)
+static void lkdtm_WRITE_RO(void)
 {
 	/* Explicitly cast away "const" for the test and make volatile. */
 	volatile unsigned long *ptr = (unsigned long *)&rodata;
@@ -89,7 +124,7 @@ void lkdtm_WRITE_RO(void)
 	pr_err("FAIL: survived bad write\n");
 }
 
-void lkdtm_WRITE_RO_AFTER_INIT(void)
+static void lkdtm_WRITE_RO_AFTER_INIT(void)
 {
 	volatile unsigned long *ptr = &ro_after_init;
 
@@ -108,13 +143,14 @@ void lkdtm_WRITE_RO_AFTER_INIT(void)
 	pr_err("FAIL: survived bad write\n");
 }
 
-void lkdtm_WRITE_KERN(void)
+static void lkdtm_WRITE_KERN(void)
 {
 	size_t size;
 	volatile unsigned char *ptr;
 
-	size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
-	ptr = (unsigned char *)do_overwritten;
+	size = (unsigned long)dereference_function_descriptor(do_overwritten) -
+	       (unsigned long)dereference_function_descriptor(do_nothing);
+	ptr = dereference_function_descriptor(do_overwritten);
 
 	pr_info("attempting bad %zu byte write at %px\n", size, ptr);
 	memcpy((void *)ptr, (unsigned char *)do_nothing, size);
@@ -124,37 +160,55 @@ void lkdtm_WRITE_KERN(void)
 	do_overwritten();
 }
 
-void lkdtm_EXEC_DATA(void)
+static void lkdtm_WRITE_OPD(void)
+{
+	size_t size = sizeof(func_desc_t);
+	void (*func)(void) = do_nothing;
+
+	if (!have_function_descriptors()) {
+		pr_info("XFAIL: Platform doesn't use function descriptors.\n");
+		return;
+	}
+	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
+	memcpy(do_nothing, do_almost_nothing, size);
+	pr_err("FAIL: survived bad write\n");
+
+	asm("" : "=m"(func));
+	func();
+}
+
+static void lkdtm_EXEC_DATA(void)
 {
 	execute_location(data_area, CODE_WRITE);
 }
 
-void lkdtm_EXEC_STACK(void)
+static void lkdtm_EXEC_STACK(void)
 {
 	u8 stack_area[EXEC_SIZE];
 	execute_location(stack_area, CODE_WRITE);
 }
 
-void lkdtm_EXEC_KMALLOC(void)
+static void lkdtm_EXEC_KMALLOC(void)
 {
 	u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
 	execute_location(kmalloc_area, CODE_WRITE);
 	kfree(kmalloc_area);
 }
 
-void lkdtm_EXEC_VMALLOC(void)
+static void lkdtm_EXEC_VMALLOC(void)
 {
 	u32 *vmalloc_area = vmalloc(EXEC_SIZE);
 	execute_location(vmalloc_area, CODE_WRITE);
 	vfree(vmalloc_area);
 }
 
-void lkdtm_EXEC_RODATA(void)
+static void lkdtm_EXEC_RODATA(void)
 {
-	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+	execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing),
+			 CODE_AS_IS);
 }
 
-void lkdtm_EXEC_USERSPACE(void)
+static void lkdtm_EXEC_USERSPACE(void)
 {
 	unsigned long user_addr;
 
@@ -169,12 +223,12 @@ void lkdtm_EXEC_USERSPACE(void)
 	vm_munmap(user_addr, PAGE_SIZE);
 }
 
-void lkdtm_EXEC_NULL(void)
+static void lkdtm_EXEC_NULL(void)
 {
 	execute_location(NULL, CODE_AS_IS);
 }
 
-void lkdtm_ACCESS_USERSPACE(void)
+static void lkdtm_ACCESS_USERSPACE(void)
 {
 	unsigned long user_addr, tmp = 0;
 	unsigned long *ptr;
@@ -207,7 +261,7 @@ void lkdtm_ACCESS_USERSPACE(void)
 	vm_munmap(user_addr, PAGE_SIZE);
 }
 
-void lkdtm_ACCESS_NULL(void)
+static void lkdtm_ACCESS_NULL(void)
 {
 	unsigned long tmp;
 	volatile unsigned long *ptr = (unsigned long *)NULL;
@@ -224,6 +278,29 @@ void lkdtm_ACCESS_NULL(void)
 
 void __init lkdtm_perms_init(void)
 {
+	do_nothing_ptr = dereference_function_descriptor(do_nothing);
+
 	/* Make sure we can write to __ro_after_init values during __init */
 	ro_after_init |= 0xAA;
 }
+
+static struct crashtype crashtypes[] = {
+	CRASHTYPE(WRITE_RO),
+	CRASHTYPE(WRITE_RO_AFTER_INIT),
+	CRASHTYPE(WRITE_KERN),
+	CRASHTYPE(WRITE_OPD),
+	CRASHTYPE(EXEC_DATA),
+	CRASHTYPE(EXEC_STACK),
+	CRASHTYPE(EXEC_KMALLOC),
+	CRASHTYPE(EXEC_VMALLOC),
+	CRASHTYPE(EXEC_RODATA),
+	CRASHTYPE(EXEC_USERSPACE),
+	CRASHTYPE(EXEC_NULL),
+	CRASHTYPE(ACCESS_USERSPACE),
+	CRASHTYPE(ACCESS_NULL),
+};
+
+struct crashtype_category perms_crashtypes = {
+	.crashtypes = crashtypes,
+	.len	    = ARRAY_SIZE(crashtypes),
+};