// SPDX-License-Identifier: GPL-2.0/* * Clang Control Flow Integrity (CFI) error and slowpath handling. * * Copyright (C) 2021 Google LLC */ #include <linux/hardirq.h>#include <linux/kallsyms.h>#include <linux/module.h>#include <linux/mutex.h>#include <linux/printk.h>#include <linux/ratelimit.h>#include <linux/rcupdate.h>#include <linux/vmalloc.h>#include <asm/cacheflush.h>#include <asm/set_memory.h> /* Compiler-defined handler names */#ifdef CONFIG_CFI_PERMISSIVE#define cfi_failure_handler	__ubsan_handle_cfi_check_fail#else#define cfi_failure_handler	__ubsan_handle_cfi_check_fail_abort#endif static inline void handle_cfi_failure(void *ptr){	if (IS_ENABLED(CONFIG_CFI_PERMISSIVE))		WARN_RATELIMIT(1, "CFI failure (target: %pS):\n", ptr);	else		panic("CFI failure (target: %pS)\n", ptr);} #ifdef CONFIG_MODULES#ifdef CONFIG_CFI_CLANG_SHADOW/* * Index type. A 16-bit index can address at most (2^16)-2 pages (taking * into account SHADOW_INVALID), i.e. ~256M with 4k pages. */typedef u16 shadow_t;#define SHADOW_INVALID		((shadow_t)~0UL) struct cfi_shadow {	/* Page index for the beginning of the shadow */	unsigned long base;	/* An array of __cfi_check locations (as indices to the shadow) */	shadow_t shadow[1];} __packed; /* * The shadow covers ~128M from the beginning of the module region. If * the region is larger, we fall back to __module_address for the rest. */#define __SHADOW_RANGE		(_UL(SZ_128M) >> PAGE_SHIFT) /* The in-memory size of struct cfi_shadow, always at least one page */#define __SHADOW_PAGES		((__SHADOW_RANGE * sizeof(shadow_t)) >> PAGE_SHIFT)#define SHADOW_PAGES		max(1UL, __SHADOW_PAGES)#define SHADOW_SIZE		(SHADOW_PAGES << PAGE_SHIFT) /* The actual size of the shadow array, minus metadata */#define SHADOW_ARR_SIZE		(SHADOW_SIZE - offsetof(struct cfi_shadow, shadow))#define SHADOW_ARR_SLOTS	(SHADOW_ARR_SIZE / sizeof(shadow_t)) static DEFINE_MUTEX(shadow_update_lock);static struct cfi_shadow __rcu *cfi_shadow __read_mostly; /* Returns the index in the shadow for the given address */static inline int ptr_to_shadow(const struct cfi_shadow *s, unsigned long ptr){	unsigned long index;	unsigned long page = ptr >> PAGE_SHIFT; 	if (unlikely(page < s->base))		return -1; /* Outside of module area */ 	index = page - s->base; 	if (index >= SHADOW_ARR_SLOTS)		return -1; /* Cannot be addressed with shadow */ 	return (int)index;} /* Returns the page address for an index in the shadow */static inline unsigned long shadow_to_ptr(const struct cfi_shadow *s,	int index){	if (unlikely(index < 0 || index >= SHADOW_ARR_SLOTS))		return 0; 	return (s->base + index) << PAGE_SHIFT;} /* Returns the __cfi_check function address for the given shadow location */static inline unsigned long shadow_to_check_fn(const struct cfi_shadow *s,	int index){	if (unlikely(index < 0 || index >= SHADOW_ARR_SLOTS))		return 0; 	if (unlikely(s->shadow[index] == SHADOW_INVALID))		return 0; 	/* __cfi_check is always page aligned */	return (s->base + s->shadow[index]) << PAGE_SHIFT;} static void prepare_next_shadow(const struct cfi_shadow __rcu *prev,		struct cfi_shadow *next){	int i, index, check; 	/* Mark everything invalid */	memset(next->shadow, 0xFF, SHADOW_ARR_SIZE); 	if (!prev)		return; /* No previous shadow */ 	/* If the base address didn't change, an update is not needed */	if (prev->base == next->base) {		memcpy(next->shadow, prev->shadow, SHADOW_ARR_SIZE);		return;	} 	/* Convert the previous shadow to the new address range */	for (i = 0; i < SHADOW_ARR_SLOTS; ++i) {		if (prev->shadow[i] == SHADOW_INVALID)			continue; 		index = ptr_to_shadow(next, shadow_to_ptr(prev, i));		if (index < 0)			continue; 		check = ptr_to_shadow(next,				shadow_to_check_fn(prev, prev->shadow[i]));		if (check < 0)			continue; 		next->shadow[index] = (shadow_t)check;	}} static void add_module_to_shadow(struct cfi_shadow *s, struct module *mod,			unsigned long min_addr, unsigned long max_addr){	int check_index;	unsigned long check = (unsigned long)mod->cfi_check;	unsigned long ptr; 	if (unlikely(!PAGE_ALIGNED(check))) {		pr_warn("cfi: not using shadow for module %s\n", mod->name);		return;	} 	check_index = ptr_to_shadow(s, check);	if (check_index < 0)		return; /* Module not addressable with shadow */ 	/* For each page, store the check function index in the shadow */	for (ptr = min_addr; ptr <= max_addr; ptr += PAGE_SIZE) {		int index = ptr_to_shadow(s, ptr); 		if (index >= 0) {			/* Each page must only contain one module */			WARN_ON_ONCE(s->shadow[index] != SHADOW_INVALID);			s->shadow[index] = (shadow_t)check_index;		}	}} static void remove_module_from_shadow(struct cfi_shadow *s, struct module *mod,		unsigned long min_addr, unsigned long max_addr){	unsigned long ptr; 	for (ptr = min_addr; ptr <= max_addr; ptr += PAGE_SIZE) {		int index = ptr_to_shadow(s, ptr); 		if (index >= 0)			s->shadow[index] = SHADOW_INVALID;	}} typedef void (*update_shadow_fn)(struct cfi_shadow *, struct module *,			unsigned long min_addr, unsigned long max_addr); static void update_shadow(struct module *mod, unsigned long base_addr,		update_shadow_fn fn){	struct cfi_shadow *prev;	struct cfi_shadow *next;	unsigned long min_addr, max_addr; 	next = vmalloc(SHADOW_SIZE); 	mutex_lock(&shadow_update_lock);	prev = rcu_dereference_protected(cfi_shadow,					 mutex_is_locked(&shadow_update_lock)); 	if (next) {		next->base = base_addr >> PAGE_SHIFT;		prepare_next_shadow(prev, next); 		min_addr = (unsigned long)mod->core_layout.base;		max_addr = min_addr + mod->core_layout.text_size;		fn(next, mod, min_addr & PAGE_MASK, max_addr & PAGE_MASK); 		set_memory_ro((unsigned long)next, SHADOW_PAGES);	} 	rcu_assign_pointer(cfi_shadow, next);	mutex_unlock(&shadow_update_lock);	synchronize_rcu(); 	if (prev) {		set_memory_rw((unsigned long)prev, SHADOW_PAGES);		vfree(prev);	}} void cfi_module_add(struct module *mod, unsigned long base_addr){	update_shadow(mod, base_addr, add_module_to_shadow);} void cfi_module_remove(struct module *mod, unsigned long base_addr){	update_shadow(mod, base_addr, remove_module_from_shadow);} static inline cfi_check_fn ptr_to_check_fn(const struct cfi_shadow __rcu *s,	unsigned long ptr){	int index; 	if (unlikely(!s))		return NULL; /* No shadow available */ 	index = ptr_to_shadow(s, ptr);	if (index < 0)		return NULL; /* Cannot be addressed with shadow */ 	return (cfi_check_fn)shadow_to_check_fn(s, index);} static inline cfi_check_fn find_shadow_check_fn(unsigned long ptr){	cfi_check_fn fn; 	rcu_read_lock_sched_notrace();	fn = ptr_to_check_fn(rcu_dereference_sched(cfi_shadow), ptr);	rcu_read_unlock_sched_notrace(); 	return fn;} #else /* !CONFIG_CFI_CLANG_SHADOW */ static inline cfi_check_fn find_shadow_check_fn(unsigned long ptr){	return NULL;} #endif /* CONFIG_CFI_CLANG_SHADOW */ static inline cfi_check_fn find_module_check_fn(unsigned long ptr){	cfi_check_fn fn = NULL;	struct module *mod; 	rcu_read_lock_sched_notrace();	mod = __module_address(ptr);	if (mod)		fn = mod->cfi_check;	rcu_read_unlock_sched_notrace(); 	return fn;} static inline cfi_check_fn find_check_fn(unsigned long ptr){	cfi_check_fn fn = NULL; 	if (is_kernel_text(ptr))		return __cfi_check; 	/*	 * Indirect call checks can happen when RCU is not watching. Both	 * the shadow and __module_address use RCU, so we need to wake it	 * up if necessary.	 */	RCU_NONIDLE({		if (IS_ENABLED(CONFIG_CFI_CLANG_SHADOW))			fn = find_shadow_check_fn(ptr); 		if (!fn)			fn = find_module_check_fn(ptr);	}); 	return fn;} void __cfi_slowpath_diag(uint64_t id, void *ptr, void *diag){	cfi_check_fn fn = find_check_fn((unsigned long)ptr); 	if (likely(fn))		fn(id, ptr, diag);	else /* Don't allow unchecked modules */		handle_cfi_failure(ptr);}EXPORT_SYMBOL(__cfi_slowpath_diag); #else /* !CONFIG_MODULES */ void __cfi_slowpath_diag(uint64_t id, void *ptr, void *diag){	handle_cfi_failure(ptr); /* No modules */}EXPORT_SYMBOL(__cfi_slowpath_diag); #endif /* CONFIG_MODULES */ void cfi_failure_handler(void *data, void *ptr, void *vtable){	handle_cfi_failure(ptr);}EXPORT_SYMBOL(cfi_failure_handler);