// SPDX-License-Identifier: GPL-2.0/* * This is for all the tests related to copy_to_user() and copy_from_user() * hardening. */#include "lkdtm.h"#include <linux/slab.h>#include <linux/highmem.h>#include <linux/vmalloc.h>#include <linux/sched/task_stack.h>#include <linux/mman.h>#include <linux/uaccess.h>#include <asm/cacheflush.h> /* * 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;static volatile size_t cache_size = 1024;static struct kmem_cache *whitelist_cache; static const unsigned char test_text[] = "This is a test.\n"; /* * Instead of adding -Wno-return-local-addr, just pass the stack address * through a function to obfuscate it from the compiler. */static noinline unsigned char *trick_compiler(unsigned char *stack){	return stack + unconst;} static noinline unsigned char *do_usercopy_stack_callee(int value){	unsigned char buf[128];	int i; 	/* Exercise stack to avoid everything living in registers. */	for (i = 0; i < sizeof(buf); i++) {		buf[i] = value & 0xff;	} 	/*	 * Put the target buffer in the middle of stack allocation	 * so that we don't step on future stack users regardless	 * of stack growth direction.	 */	return trick_compiler(&buf[(128/2)-32]);} static noinline void do_usercopy_stack(bool to_user, bool bad_frame){	unsigned long user_addr;	unsigned char good_stack[32];	unsigned char *bad_stack;	int i; 	/* Exercise stack to avoid everything living in registers. */	for (i = 0; i < sizeof(good_stack); i++)		good_stack[i] = test_text[i % sizeof(test_text)]; 	/* This is a pointer to outside our current stack frame. */	if (bad_frame) {		bad_stack = do_usercopy_stack_callee((uintptr_t)&bad_stack);	} else {		/* Put start address just inside stack. */		bad_stack = task_stack_page(current) + THREAD_SIZE;		bad_stack -= sizeof(unsigned long);	} #ifdef ARCH_HAS_CURRENT_STACK_POINTER	pr_info("stack     : %px\n", (void *)current_stack_pointer);#endif	pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack));	pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack)); 	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 (to_user) {		pr_info("attempting good copy_to_user of local stack\n");		if (copy_to_user((void __user *)user_addr, 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,				 unconst + sizeof(good_stack))) {			pr_warn("copy_to_user failed, but lacked Oops\n");			goto free_user;		}	} else {		/*		 * There isn't a safe way to not be protected by usercopy		 * if we're going to write to another thread's stack.		 */		if (!bad_frame)			goto free_user; 		pr_info("attempting good copy_from_user of local stack\n");		if (copy_from_user(good_stack, (void __user *)user_addr,				   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,				   unconst + sizeof(good_stack))) {			pr_warn("copy_from_user failed, but lacked Oops\n");			goto free_user;		}	} free_user:	vm_munmap(user_addr, PAGE_SIZE);} /* * This checks for whole-object size validation with hardened usercopy, * with or without usercopy whitelisting. */static void do_usercopy_slab_size(bool to_user){	unsigned long user_addr;	unsigned char *one, *two;	void __user *test_user_addr;	void *test_kern_addr;	size_t size = unconst + 1024; 	one = kmalloc(size, GFP_KERNEL);	two = kmalloc(size, GFP_KERNEL);	if (!one || !two) {		pr_warn("Failed to allocate kernel memory\n");		goto free_kernel;	} 	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");		goto free_kernel;	} 	memset(one, 'A', size);	memset(two, 'B', size); 	test_user_addr = (void __user *)(user_addr + 16);	test_kern_addr = one + 16; 	if (to_user) {		pr_info("attempting good copy_to_user of correct size\n");		if (copy_to_user(test_user_addr, test_kern_addr, size / 2)) {			pr_warn("copy_to_user failed unexpectedly?!\n");			goto free_user;		} 		pr_info("attempting bad copy_to_user of too large size\n");		if (copy_to_user(test_user_addr, test_kern_addr, size)) {			pr_warn("copy_to_user failed, but lacked Oops\n");			goto free_user;		}	} else {		pr_info("attempting good copy_from_user of correct size\n");		if (copy_from_user(test_kern_addr, test_user_addr, size / 2)) {			pr_warn("copy_from_user failed unexpectedly?!\n");			goto free_user;		} 		pr_info("attempting bad copy_from_user of too large size\n");		if (copy_from_user(test_kern_addr, test_user_addr, size)) {			pr_warn("copy_from_user failed, but lacked Oops\n");			goto free_user;		}	}	pr_err("FAIL: bad usercopy not detected!\n");	pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy"); free_user:	vm_munmap(user_addr, PAGE_SIZE);free_kernel:	kfree(one);	kfree(two);} /* * This checks for the specific whitelist window within an object. If this * test passes, then do_usercopy_slab_size() tests will pass too. */static void do_usercopy_slab_whitelist(bool to_user){	unsigned long user_alloc;	unsigned char *buf = NULL;	unsigned char __user *user_addr;	size_t offset, size; 	/* Make sure cache was prepared. */	if (!whitelist_cache) {		pr_warn("Failed to allocate kernel cache\n");		return;	} 	/*	 * Allocate a buffer with a whitelisted window in the buffer.	 */	buf = kmem_cache_alloc(whitelist_cache, GFP_KERNEL);	if (!buf) {		pr_warn("Failed to allocate buffer from whitelist cache\n");		goto free_alloc;	} 	/* Allocate user memory we'll poke at. */	user_alloc = vm_mmap(NULL, 0, PAGE_SIZE,			    PROT_READ | PROT_WRITE | PROT_EXEC,			    MAP_ANONYMOUS | MAP_PRIVATE, 0);	if (user_alloc >= TASK_SIZE) {		pr_warn("Failed to allocate user memory\n");		goto free_alloc;	}	user_addr = (void __user *)user_alloc; 	memset(buf, 'B', cache_size); 	/* Whitelisted window in buffer, from kmem_cache_create_usercopy. */	offset = (cache_size / 4) + unconst;	size = (cache_size / 16) + unconst; 	if (to_user) {		pr_info("attempting good copy_to_user inside whitelist\n");		if (copy_to_user(user_addr, buf + offset, size)) {			pr_warn("copy_to_user failed unexpectedly?!\n");			goto free_user;		} 		pr_info("attempting bad copy_to_user outside whitelist\n");		if (copy_to_user(user_addr, buf + offset - 1, size)) {			pr_warn("copy_to_user failed, but lacked Oops\n");			goto free_user;		}	} else {		pr_info("attempting good copy_from_user inside whitelist\n");		if (copy_from_user(buf + offset, user_addr, size)) {			pr_warn("copy_from_user failed unexpectedly?!\n");			goto free_user;		} 		pr_info("attempting bad copy_from_user outside whitelist\n");		if (copy_from_user(buf + offset - 1, user_addr, size)) {			pr_warn("copy_from_user failed, but lacked Oops\n");			goto free_user;		}	}	pr_err("FAIL: bad usercopy not detected!\n");	pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy"); free_user:	vm_munmap(user_alloc, PAGE_SIZE);free_alloc:	if (buf)		kmem_cache_free(whitelist_cache, buf);} /* Callable tests. */static void lkdtm_USERCOPY_SLAB_SIZE_TO(void){	do_usercopy_slab_size(true);} static void lkdtm_USERCOPY_SLAB_SIZE_FROM(void){	do_usercopy_slab_size(false);} static void lkdtm_USERCOPY_SLAB_WHITELIST_TO(void){	do_usercopy_slab_whitelist(true);} static void lkdtm_USERCOPY_SLAB_WHITELIST_FROM(void){	do_usercopy_slab_whitelist(false);} static void lkdtm_USERCOPY_STACK_FRAME_TO(void){	do_usercopy_stack(true, true);} static void lkdtm_USERCOPY_STACK_FRAME_FROM(void){	do_usercopy_stack(false, true);} static void lkdtm_USERCOPY_STACK_BEYOND(void){	do_usercopy_stack(true, false);} static void lkdtm_USERCOPY_KERNEL(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;	} 	pr_info("attempting good copy_to_user from kernel rodata: %px\n",		test_text);	if (copy_to_user((void __user *)user_addr, 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: %px\n",		vm_mmap);	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;	}	pr_err("FAIL: bad copy_to_user() not detected!\n");	pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy"); free_user:	vm_munmap(user_addr, PAGE_SIZE);} /* * This expects "kaddr" to point to a PAGE_SIZE allocation, which means * a more complete test that would include copy_from_user() would risk * memory corruption. Just test copy_to_user() here, as that exercises * almost exactly the same code paths. */static void do_usercopy_page_span(const char *name, void *kaddr){	unsigned long uaddr; 	uaddr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE,			MAP_ANONYMOUS | MAP_PRIVATE, 0);	if (uaddr >= TASK_SIZE) {		pr_warn("Failed to allocate user memory\n");		return;	} 	/* Initialize contents. */	memset(kaddr, 0xAA, PAGE_SIZE); 	/* Bump the kaddr forward to detect a page-spanning overflow. */	kaddr += PAGE_SIZE / 2; 	pr_info("attempting good copy_to_user() from kernel %s: %px\n",		name, kaddr);	if (copy_to_user((void __user *)uaddr, kaddr,			 unconst + (PAGE_SIZE / 2))) {		pr_err("copy_to_user() failed unexpectedly?!\n");		goto free_user;	} 	pr_info("attempting bad copy_to_user() from kernel %s: %px\n",		name, kaddr);	if (copy_to_user((void __user *)uaddr, kaddr, unconst + PAGE_SIZE)) {		pr_warn("Good, copy_to_user() failed, but lacked Oops(?!)\n");		goto free_user;	} 	pr_err("FAIL: bad copy_to_user() not detected!\n");	pr_expected_config_param(CONFIG_HARDENED_USERCOPY, "hardened_usercopy"); free_user:	vm_munmap(uaddr, PAGE_SIZE);} static void lkdtm_USERCOPY_VMALLOC(void){	void *addr; 	addr = vmalloc(PAGE_SIZE);	if (!addr) {		pr_err("vmalloc() failed!?\n");		return;	}	do_usercopy_page_span("vmalloc", addr);	vfree(addr);} static void lkdtm_USERCOPY_FOLIO(void){	struct folio *folio;	void *addr; 	/*	 * FIXME: Folio checking currently misses 0-order allocations, so	 * allocate and bump forward to the last page.	 */	folio = folio_alloc(GFP_KERNEL | __GFP_ZERO, 1);	if (!folio) {		pr_err("folio_alloc() failed!?\n");		return;	}	addr = folio_address(folio);	if (addr)		do_usercopy_page_span("folio", addr + PAGE_SIZE);	else		pr_err("folio_address() failed?!\n");	folio_put(folio);} void __init lkdtm_usercopy_init(void){	/* Prepare cache that lacks SLAB_USERCOPY flag. */	whitelist_cache =		kmem_cache_create_usercopy("lkdtm-usercopy", cache_size,					   0, 0,					   cache_size / 4,					   cache_size / 16,					   NULL);} void __exit lkdtm_usercopy_exit(void){	kmem_cache_destroy(whitelist_cache);} static struct crashtype crashtypes[] = {	CRASHTYPE(USERCOPY_SLAB_SIZE_TO),	CRASHTYPE(USERCOPY_SLAB_SIZE_FROM),	CRASHTYPE(USERCOPY_SLAB_WHITELIST_TO),	CRASHTYPE(USERCOPY_SLAB_WHITELIST_FROM),	CRASHTYPE(USERCOPY_STACK_FRAME_TO),	CRASHTYPE(USERCOPY_STACK_FRAME_FROM),	CRASHTYPE(USERCOPY_STACK_BEYOND),	CRASHTYPE(USERCOPY_VMALLOC),	CRASHTYPE(USERCOPY_FOLIO),	CRASHTYPE(USERCOPY_KERNEL),}; struct crashtype_category usercopy_crashtypes = {	.crashtypes = crashtypes,	.len	    = ARRAY_SIZE(crashtypes),};