lkdtm: split memory permissions tests to separate file

This splits the EXEC_*, WRITE_* and related tests into the new lkdtm_perms.c
file to help separate things better for readability.

Signed-off-by: Kees Cook <keescook@chromium.org>

drivers/misc/Makefile

@@ -59,6 +59,7 @@ obj-$(CONFIG_CXL_BASE)		+= cxl/
 obj-$(CONFIG_PANEL)             += panel.o
 
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_core.o
+lkdtm-$(CONFIG_LKDTM)		+= lkdtm_perms.o
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_rodata_objcopy.o
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_usercopy.o
 

drivers/misc/lkdtm.h

@@ -1,6 +1,19 @@
 #ifndef __LKDTM_H
 #define __LKDTM_H
 
+/* lkdtm_perms.c */
+void __init lkdtm_perms_init(void);
+void lkdtm_WRITE_RO(void);
+void lkdtm_WRITE_RO_AFTER_INIT(void);
+void lkdtm_WRITE_KERN(void);
+void lkdtm_EXEC_DATA(void);
+void lkdtm_EXEC_STACK(void);
+void lkdtm_EXEC_KMALLOC(void);
+void lkdtm_EXEC_VMALLOC(void);
+void lkdtm_EXEC_RODATA(void);
+void lkdtm_EXEC_USERSPACE(void);
+void lkdtm_ACCESS_USERSPACE(void);
+
 /* lkdtm_rodata.c */
 void lkdtm_rodata_do_nothing(void);
 
@@ -16,4 +29,5 @@ void lkdtm_USERCOPY_STACK_FRAME_FROM(void);
 void lkdtm_USERCOPY_STACK_BEYOND(void);
 void lkdtm_USERCOPY_KERNEL(void);
 
+
 #endif

drivers/misc/lkdtm_core.c

@@ -44,9 +44,6 @@
 #include <linux/slab.h>
 #include <scsi/scsi_cmnd.h>
 #include <linux/debugfs.h>
-#include <linux/vmalloc.h>
-#include <linux/mman.h>
-#include <asm/cacheflush.h>
 
 #ifdef CONFIG_IDE
 #include <linux/ide.h>
@@ -67,7 +64,6 @@
 #define REC_NUM_DEFAULT ((THREAD_SIZE / REC_STACK_SIZE) * 2)
 
 #define DEFAULT_COUNT 10
-#define EXEC_SIZE 64
 
 enum cname {
 	CN_INVALID,
@@ -191,11 +187,6 @@ static int count = DEFAULT_COUNT;
 static DEFINE_SPINLOCK(count_lock);
 static DEFINE_SPINLOCK(lock_me_up);
 
-static u8 data_area[EXEC_SIZE];
-
-static const unsigned long rodata = 0xAA55AA55;
-static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
-
 module_param(recur_count, int, 0644);
 MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test");
 module_param(cpoint_name, charp, 0444);
@@ -348,18 +339,6 @@ static int recursive_loop(int remaining)
 		return recursive_loop(remaining - 1);
 }
 
-static void do_nothing(void)
-{
-	return;
-}
-
-/* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
-{
-	pr_info("do_overwritten wasn't overwritten!\n");
-	return;
-}
-
 static noinline void corrupt_stack(void)
 {
 	/* Use default char array length that triggers stack protection. */
@@ -368,38 +347,6 @@ static noinline void corrupt_stack(void)
 	memset((void *)data, 0, 64);
 }
 
-static noinline void execute_location(void *dst, bool write)
-{
-	void (*func)(void) = dst;
-
-	pr_info("attempting ok execution at %p\n", do_nothing);
-	do_nothing();
-
-	if (write) {
-		memcpy(dst, do_nothing, EXEC_SIZE);
-		flush_icache_range((unsigned long)dst,
-				   (unsigned long)dst + EXEC_SIZE);
-	}
-	pr_info("attempting bad execution at %p\n", func);
-	func();
-}
-
-static void execute_user_location(void *dst)
-{
-	/* Intentionally crossing kernel/user memory boundary. */
-	void (*func)(void) = dst;
-
-	pr_info("attempting ok execution at %p\n", do_nothing);
-	do_nothing();
-
-	if (copy_to_user((void __user *)dst, do_nothing, EXEC_SIZE))
-		return;
-	flush_icache_range((unsigned long)dst, (unsigned long)dst + EXEC_SIZE);
-	pr_info("attempting bad execution at %p\n", func);
-	func();
-}
-
-
 static void lkdtm_do_action(enum ctype which)
 {
 	switch (which) {
@@ -577,116 +524,35 @@ static void lkdtm_do_action(enum ctype which)
 		schedule();
 		break;
 	case CT_EXEC_DATA:
-		execute_location(data_area, true);
+		lkdtm_EXEC_DATA();
 		break;
-	case CT_EXEC_STACK: {
-		u8 stack_area[EXEC_SIZE];
-		execute_location(stack_area, true);
+	case CT_EXEC_STACK:
+		lkdtm_EXEC_STACK();
 		break;
-	}
-	case CT_EXEC_KMALLOC: {
-		u32 *kmalloc_area = kmalloc(EXEC_SIZE, GFP_KERNEL);
-		execute_location(kmalloc_area, true);
-		kfree(kmalloc_area);
+	case CT_EXEC_KMALLOC:
+		lkdtm_EXEC_KMALLOC();
 		break;
-	}
-	case CT_EXEC_VMALLOC: {
-		u32 *vmalloc_area = vmalloc(EXEC_SIZE);
-		execute_location(vmalloc_area, true);
-		vfree(vmalloc_area);
+	case CT_EXEC_VMALLOC:
+		lkdtm_EXEC_VMALLOC();
 		break;
-	}
 	case CT_EXEC_RODATA:
-		execute_location(lkdtm_rodata_do_nothing, false);
+		lkdtm_EXEC_RODATA();
 		break;
-	case CT_EXEC_USERSPACE: {
-		unsigned long user_addr;
-
-		user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
-				    PROT_READ | PROT_WRITE | PROT_EXEC,
-				    MAP_ANONYMOUS | MAP_PRIVATE, 0);
-		if (user_addr >= TASK_SIZE) {
-			pr_warn("Failed to allocate user memory\n");
-			return;
-		}
-		execute_user_location((void *)user_addr);
-		vm_munmap(user_addr, PAGE_SIZE);
+	case CT_EXEC_USERSPACE:
+		lkdtm_EXEC_USERSPACE();
 		break;
-	}
-	case CT_ACCESS_USERSPACE: {
-		unsigned long user_addr, tmp = 0;
-		unsigned long *ptr;
-
-		user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
-				    PROT_READ | PROT_WRITE | PROT_EXEC,
-				    MAP_ANONYMOUS | MAP_PRIVATE, 0);
-		if (user_addr >= TASK_SIZE) {
-			pr_warn("Failed to allocate user memory\n");
-			return;
-		}
-
-		if (copy_to_user((void __user *)user_addr, &tmp, sizeof(tmp))) {
-			pr_warn("copy_to_user failed\n");
-			vm_munmap(user_addr, PAGE_SIZE);
-			return;
-		}
-
-		ptr = (unsigned long *)user_addr;
-
-		pr_info("attempting bad read at %p\n", ptr);
-		tmp = *ptr;
-		tmp += 0xc0dec0de;
-
-		pr_info("attempting bad write at %p\n", ptr);
-		*ptr = tmp;
-
-		vm_munmap(user_addr, PAGE_SIZE);
-
+	case CT_ACCESS_USERSPACE:
+		lkdtm_ACCESS_USERSPACE();
 		break;
-	}
-	case CT_WRITE_RO: {
-		/* Explicitly cast away "const" for the test. */
-		unsigned long *ptr = (unsigned long *)&rodata;
-
-		pr_info("attempting bad rodata write at %p\n", ptr);
-		*ptr ^= 0xabcd1234;
-
+	case CT_WRITE_RO:
+		lkdtm_WRITE_RO();
 		break;
-	}
-	case CT_WRITE_RO_AFTER_INIT: {
-		unsigned long *ptr = &ro_after_init;
-
-		/*
-		 * Verify we were written to during init. Since an Oops
-		 * is considered a "success", a failure is to just skip the
-		 * real test.
-		 */
-		if ((*ptr & 0xAA) != 0xAA) {
-			pr_info("%p was NOT written during init!?\n", ptr);
-			break;
-		}
-
-		pr_info("attempting bad ro_after_init write at %p\n", ptr);
-		*ptr ^= 0xabcd1234;
-
+	case CT_WRITE_RO_AFTER_INIT:
+		lkdtm_WRITE_RO_AFTER_INIT();
 		break;
-	}
-	case CT_WRITE_KERN: {
-		size_t size;
-		unsigned char *ptr;
-
-		size = (unsigned long)do_overwritten -
-		       (unsigned long)do_nothing;
-		ptr = (unsigned char *)do_overwritten;
-
-		pr_info("attempting bad %zu byte write at %p\n", size, ptr);
-		memcpy(ptr, (unsigned char *)do_nothing, size);
-		flush_icache_range((unsigned long)ptr,
-				   (unsigned long)(ptr + size));
-
-		do_overwritten();
+	case CT_WRITE_KERN:
+		lkdtm_WRITE_KERN();
 		break;
-	}
 	case CT_ATOMIC_UNDERFLOW: {
 		atomic_t under = ATOMIC_INIT(INT_MIN);
 
@@ -1024,11 +890,9 @@ static int __init lkdtm_module_init(void)
 	int i;
 
 	/* Handle test-specific initialization. */
+	lkdtm_perms_init();
 	lkdtm_usercopy_init();
 
-	/* Make sure we can write to __ro_after_init values during __init */
-	ro_after_init |= 0xAA;
-
 	/* Register debugfs interface */
 	lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);
 	if (!lkdtm_debugfs_root) {

drivers/misc/lkdtm_perms.c

@@ -0,0 +1,203 @@
+/*
+ * This is for all the tests related to validating kernel memory
+ * permissions: non-executable regions, non-writable regions, and
+ * even non-readable regions.
+ */
+#define pr_fmt(fmt) "lkdtm: " fmt
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/mman.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+
+#include "lkdtm.h"
+
+/* Whether or not to fill the target memory area with do_nothing(). */
+#define CODE_WRITE	true
+#define CODE_AS_IS	false
+
+/* How many bytes to copy to be sure we've copied enough of do_nothing(). */
+#define EXEC_SIZE 64
+
+/* 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. */
+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 just returns to the caller. It is designed to be copied into
+ * non-executable memory regions.
+ */
+static void do_nothing(void)
+{
+	return;
+}
+
+/* Must immediately follow do_nothing for size calculuations to work out. */
+static void do_overwritten(void)
+{
+	pr_info("do_overwritten wasn't overwritten!\n");
+	return;
+}
+
+static noinline void execute_location(void *dst, bool write)
+{
+	void (*func)(void) = dst;
+
+	pr_info("attempting ok execution at %p\n", do_nothing);
+	do_nothing();
+
+	if (write == CODE_WRITE) {
+		memcpy(dst, do_nothing, EXEC_SIZE);
+		flush_icache_range((unsigned long)dst,
+				   (unsigned long)dst + EXEC_SIZE);
+	}
+	pr_info("attempting bad execution at %p\n", func);
+	func();
+}
+
+static void execute_user_location(void *dst)
+{
+	/* Intentionally crossing kernel/user memory boundary. */
+	void (*func)(void) = dst;
+
+	pr_info("attempting ok execution at %p\n", do_nothing);
+	do_nothing();
+
+	if (copy_to_user((void __user *)dst, do_nothing, EXEC_SIZE))
+		return;
+	flush_icache_range((unsigned long)dst, (unsigned long)dst + EXEC_SIZE);
+	pr_info("attempting bad execution at %p\n", func);
+	func();
+}
+
+void lkdtm_WRITE_RO(void)
+{
+	/* Explicitly cast away "const" for the test. */
+	unsigned long *ptr = (unsigned long *)&rodata;
+
+	pr_info("attempting bad rodata write at %p\n", ptr);
+	*ptr ^= 0xabcd1234;
+}
+
+void lkdtm_WRITE_RO_AFTER_INIT(void)
+{
+	unsigned long *ptr = &ro_after_init;
+
+	/*
+	 * Verify we were written to during init. Since an Oops
+	 * is considered a "success", a failure is to just skip the
+	 * real test.
+	 */
+	if ((*ptr & 0xAA) != 0xAA) {
+		pr_info("%p was NOT written during init!?\n", ptr);
+		return;
+	}
+
+	pr_info("attempting bad ro_after_init write at %p\n", ptr);
+	*ptr ^= 0xabcd1234;
+}
+
+void lkdtm_WRITE_KERN(void)
+{
+	size_t size;
+	unsigned char *ptr;
+
+	size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
+	ptr = (unsigned char *)do_overwritten;
+
+	pr_info("attempting bad %zu byte write at %p\n", size, ptr);
+	memcpy(ptr, (unsigned char *)do_nothing, size);
+	flush_icache_range((unsigned long)ptr, (unsigned long)(ptr + size));
+
+	do_overwritten();
+}
+
+void lkdtm_EXEC_DATA(void)
+{
+	execute_location(data_area, CODE_WRITE);
+}
+
+void lkdtm_EXEC_STACK(void)
+{
+	u8 stack_area[EXEC_SIZE];
+	execute_location(stack_area, CODE_WRITE);
+}
+
+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)
+{
+	u32 *vmalloc_area = vmalloc(EXEC_SIZE);
+	execute_location(vmalloc_area, CODE_WRITE);
+	vfree(vmalloc_area);
+}
+
+void lkdtm_EXEC_RODATA(void)
+{
+	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+}
+
+void lkdtm_EXEC_USERSPACE(void)
+{
+	unsigned long user_addr;
+
+	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+			    PROT_READ | PROT_WRITE | PROT_EXEC,
+			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
+	if (user_addr >= TASK_SIZE) {
+		pr_warn("Failed to allocate user memory\n");
+		return;
+	}
+	execute_user_location((void *)user_addr);
+	vm_munmap(user_addr, PAGE_SIZE);
+}
+
+void lkdtm_ACCESS_USERSPACE(void)
+{
+	unsigned long user_addr, tmp = 0;
+	unsigned long *ptr;
+
+	user_addr = vm_mmap(NULL, 0, PAGE_SIZE,
+			    PROT_READ | PROT_WRITE | PROT_EXEC,
+			    MAP_ANONYMOUS | MAP_PRIVATE, 0);
+	if (user_addr >= TASK_SIZE) {
+		pr_warn("Failed to allocate user memory\n");
+		return;
+	}
+
+	if (copy_to_user((void __user *)user_addr, &tmp, sizeof(tmp))) {
+		pr_warn("copy_to_user failed\n");
+		vm_munmap(user_addr, PAGE_SIZE);
+		return;
+	}
+
+	ptr = (unsigned long *)user_addr;
+
+	pr_info("attempting bad read at %p\n", ptr);
+	tmp = *ptr;
+	tmp += 0xc0dec0de;
+
+	pr_info("attempting bad write at %p\n", ptr);
+	*ptr = tmp;
+
+	vm_munmap(user_addr, PAGE_SIZE);
+}
+
+void __init lkdtm_perms_init(void)
+{
+	/* Make sure we can write to __ro_after_init values during __init */
+	ro_after_init |= 0xAA;
+
+}