Merge tag 'kcfi-v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull kcfi updates from Kees Cook:
 "This replaces the prior support for Clang's standard Control Flow
  Integrity (CFI) instrumentation, which has required a lot of special
  conditions (e.g. LTO) and work-arounds.

  The new implementation ("Kernel CFI") is specific to C, directly
  designed for the Linux kernel, and takes advantage of architectural
  features like x86's IBT. This series retains arm64 support and adds
  x86 support.

  GCC support is expected in the future[1], and additional "generic"
  architectural support is expected soon[2].

  Summary:

   - treewide: Remove old CFI support details

   - arm64: Replace Clang CFI support with Clang KCFI support

   - x86: Introduce Clang KCFI support"

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107048 [1]
Link: https://github.com/samitolvanen/llvm-project/commits/kcfi_generic [2]

* tag 'kcfi-v6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (22 commits)
  x86: Add support for CONFIG_CFI_CLANG
  x86/purgatory: Disable CFI
  x86: Add types to indirectly called assembly functions
  x86/tools/relocs: Ignore __kcfi_typeid_ relocations
  kallsyms: Drop CONFIG_CFI_CLANG workarounds
  objtool: Disable CFI warnings
  objtool: Preserve special st_shndx indexes in elf_update_symbol
  treewide: Drop __cficanonical
  treewide: Drop WARN_ON_FUNCTION_MISMATCH
  treewide: Drop function_nocfi
  init: Drop __nocfi from __init
  arm64: Drop unneeded __nocfi attributes
  arm64: Add CFI error handling
  arm64: Add types to indirect called assembly functions
  psci: Fix the function type for psci_initcall_t
  lkdtm: Emit an indirect call for CFI tests
  cfi: Add type helper macros
  cfi: Switch to -fsanitize=kcfi
  cfi: Drop __CFI_ADDRESSABLE
  cfi: Remove CONFIG_CFI_CLANG_SHADOW
  ...

5 files changed, 62 insertions, 362 deletions

diff --git a/kernel/cfi.c b/kernel/cfi.c
index 2046276ee234..08caad776717 100644
--- a/kernel/cfi.c
+++ b/kernel/cfi.c
@@ -1,339 +1,101 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Clang Control Flow Integrity (CFI) error and slowpath handling.
+ * Clang Control Flow Integrity (CFI) error handling.
  *
- * Copyright (C) 2021 Google LLC
+ * Copyright (C) 2022 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>
+#include <linux/cfi.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)
+enum bug_trap_type report_cfi_failure(struct pt_regs *regs, unsigned long addr,
+				      unsigned long *target, u32 type)
 {
-	if (IS_ENABLED(CONFIG_CFI_PERMISSIVE))
-		WARN_RATELIMIT(1, "CFI failure (target: %pS):\n", ptr);
+	if (target)
+		pr_err("CFI failure at %pS (target: %pS; expected type: 0x%08x)\n",
+		       (void *)addr, (void *)*target, type);
 	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;
+		pr_err("CFI failure at %pS (no target information)\n",
+		       (void *)addr);
 
-/* 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;
+	if (IS_ENABLED(CONFIG_CFI_PERMISSIVE)) {
+		__warn(NULL, 0, (void *)addr, 0, regs, NULL);
+		return BUG_TRAP_TYPE_WARN;
 	}
 
-	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;
-		}
-	}
+	return BUG_TRAP_TYPE_BUG;
 }
 
-static void remove_module_from_shadow(struct cfi_shadow *s, struct module *mod,
-		unsigned long min_addr, unsigned long max_addr)
+#ifdef CONFIG_ARCH_USES_CFI_TRAPS
+static inline unsigned long trap_address(s32 *p)
 {
-	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;
-	}
+	return (unsigned long)((long)p + (long)*p);
 }
 
-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)
+static bool is_trap(unsigned long addr, s32 *start, s32 *end)
 {
-	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);
+	s32 *p;
 
-		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);
+	for (p = start; p < end; ++p) {
+		if (trap_address(p) == addr)
+			return true;
 	}
-}
 
-void cfi_module_add(struct module *mod, unsigned long base_addr)
-{
-	update_shadow(mod, base_addr, add_module_to_shadow);
+	return false;
 }
 
-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)
+#ifdef CONFIG_MODULES
+/* Populates `kcfi_trap(_end)?` fields in `struct module`. */
+void module_cfi_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
+			 struct module *mod)
 {
-	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 */
+	char *secstrings;
+	unsigned int i;
 
-	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;
+	mod->kcfi_traps = NULL;
+	mod->kcfi_traps_end = NULL;
 
-	rcu_read_lock_sched_notrace();
-	fn = ptr_to_check_fn(rcu_dereference_sched(cfi_shadow), ptr);
-	rcu_read_unlock_sched_notrace();
+	secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 
-	return fn;
-}
-
-#else /* !CONFIG_CFI_CLANG_SHADOW */
+	for (i = 1; i < hdr->e_shnum; i++) {
+		if (strcmp(secstrings + sechdrs[i].sh_name, "__kcfi_traps"))
+			continue;
 
-static inline cfi_check_fn find_shadow_check_fn(unsigned long ptr)
-{
-	return NULL;
+		mod->kcfi_traps = (s32 *)sechdrs[i].sh_addr;
+		mod->kcfi_traps_end = (s32 *)(sechdrs[i].sh_addr + sechdrs[i].sh_size);
+		break;
+	}
 }
 
-#endif /* CONFIG_CFI_CLANG_SHADOW */
-
-static inline cfi_check_fn find_module_check_fn(unsigned long ptr)
+static bool is_module_cfi_trap(unsigned long addr)
 {
-	cfi_check_fn fn = NULL;
 	struct module *mod;
+	bool found = false;
 
 	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;
-	unsigned long flags;
-	bool rcu_idle;
-
-	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_idle = !rcu_is_watching();
-	if (rcu_idle) {
-		local_irq_save(flags);
-		ct_irq_enter();
-	}
-
-	if (IS_ENABLED(CONFIG_CFI_CLANG_SHADOW))
-		fn = find_shadow_check_fn(ptr);
-	if (!fn)
-		fn = find_module_check_fn(ptr);
+	mod = __module_address(addr);
+	if (mod)
+		found = is_trap(addr, mod->kcfi_traps, mod->kcfi_traps_end);
 
-	if (rcu_idle) {
-		ct_irq_exit();
-		local_irq_restore(flags);
-	}
+	rcu_read_unlock_sched_notrace();
 
-	return fn;
+	return found;
 }
-
-void __cfi_slowpath_diag(uint64_t id, void *ptr, void *diag)
+#else /* CONFIG_MODULES */
+static inline bool is_module_cfi_trap(unsigned long addr)
 {
-	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);
+	return false;
 }
-EXPORT_SYMBOL(__cfi_slowpath_diag);
+#endif /* CONFIG_MODULES */
 
-#else /* !CONFIG_MODULES */
+extern s32 __start___kcfi_traps[];
+extern s32 __stop___kcfi_traps[];
 
-void __cfi_slowpath_diag(uint64_t id, void *ptr, void *diag)
+bool is_cfi_trap(unsigned long addr)
 {
-	handle_cfi_failure(ptr); /* No modules */
-}
-EXPORT_SYMBOL(__cfi_slowpath_diag);
+	if (is_trap(addr, __start___kcfi_traps, __stop___kcfi_traps))
+		return true;
 
-#endif /* CONFIG_MODULES */
-
-void cfi_failure_handler(void *data, void *ptr, void *vtable)
-{
-	handle_cfi_failure(ptr);
+	return is_module_cfi_trap(addr);
 }
-EXPORT_SYMBOL(cfi_failure_handler);
+#endif /* CONFIG_ARCH_USES_CFI_TRAPS */
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index fc5e26348d25..60c20f301a6b 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -177,7 +177,6 @@ static bool cleanup_symbol_name(char *s)
 	 * character in an identifier in C. Suffixes observed:
 	 * - foo.llvm.[0-9a-f]+
 	 * - foo.[0-9a-f]+
-	 * - foo.[0-9a-f]+.cfi_jt
 	 */
 	res = strchr(s, '.');
 	if (res) {
@@ -185,22 +184,6 @@ static bool cleanup_symbol_name(char *s)
 		return true;
 	}
 
-	if (!IS_ENABLED(CONFIG_CFI_CLANG) ||
-	    !IS_ENABLED(CONFIG_LTO_CLANG_THIN) ||
-	    CONFIG_CLANG_VERSION >= 130000)
-		return false;
-
-	/*
-	 * Prior to LLVM 13, the following suffixes were observed when thinLTO
-	 * and CFI are both enabled:
-	 * - foo$[0-9]+
-	 */
-	res = strrchr(s, '$');
-	if (res) {
-		*res = '\0';
-		return true;
-	}
-
 	return false;
 }
 
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3c677918d8f2..28a6b7ab4a0f 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -1050,8 +1050,7 @@ static void __kthread_queue_delayed_work(struct kthread_worker *worker,
 	struct timer_list *timer = &dwork->timer;
 	struct kthread_work *work = &dwork->work;
 
-	WARN_ON_FUNCTION_MISMATCH(timer->function,
-				  kthread_delayed_work_timer_fn);
+	WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
 
 	/*
 	 * If @delay is 0, queue @dwork->work immediately.  This is for
diff --git a/kernel/module/main.c b/kernel/module/main.c
index a4e4d84b6f4e..70c0b2c6fef8 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -53,6 +53,7 @@
 #include <linux/bsearch.h>
 #include <linux/dynamic_debug.h>
 #include <linux/audit.h>
+#include <linux/cfi.h>
 #include <uapi/linux/module.h>
 #include "internal.h"
 
@@ -1144,8 +1145,6 @@ void __weak module_arch_freeing_init(struct module *mod)
 {
 }
 
-static void cfi_cleanup(struct module *mod);
-
 /* Free a module, remove from lists, etc. */
 static void free_module(struct module *mod)
 {
@@ -1190,9 +1189,6 @@ static void free_module(struct module *mod)
 		       mod->name);
 	mutex_unlock(&module_mutex);
 
-	/* Clean up CFI for the module. */
-	cfi_cleanup(mod);
-
 	/* This may be empty, but that's OK */
 	module_arch_freeing_init(mod);
 	module_memfree(mod->init_layout.base);
@@ -2602,8 +2598,9 @@ static int complete_formation(struct module *mod, struct load_info *info)
 	if (err < 0)
 		goto out;
 
-	/* This relies on module_mutex for list integrity. */
+	/* These rely on module_mutex for list integrity. */
 	module_bug_finalize(info->hdr, info->sechdrs, mod);
+	module_cfi_finalize(info->hdr, info->sechdrs, mod);
 
 	if (module_check_misalignment(mod))
 		goto out_misaligned;
@@ -2665,8 +2662,6 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
 	return 0;
 }
 
-static void cfi_init(struct module *mod);
-
 /*
  * Allocate and load the module: note that size of section 0 is always
  * zero, and we rely on this for optional sections.
@@ -2796,9 +2791,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
 
 	flush_module_icache(mod);
 
-	/* Setup CFI for the module. */
-	cfi_init(mod);
-
 	/* Now copy in args */
 	mod->args = strndup_user(uargs, ~0UL >> 1);
 	if (IS_ERR(mod->args)) {
@@ -2875,7 +2867,6 @@ static int load_module(struct load_info *info, const char __user *uargs,
 	synchronize_rcu();
 	kfree(mod->args);
  free_arch_cleanup:
-	cfi_cleanup(mod);
 	module_arch_cleanup(mod);
  free_modinfo:
 	free_modinfo(mod);
@@ -2961,41 +2952,6 @@ static inline int within(unsigned long addr, void *start, unsigned long size)
 	return ((void *)addr >= start && (void *)addr < start + size);
 }
 
-static void cfi_init(struct module *mod)
-{
-#ifdef CONFIG_CFI_CLANG
-	initcall_t *init;
-#ifdef CONFIG_MODULE_UNLOAD
-	exitcall_t *exit;
-#endif
-
-	rcu_read_lock_sched();
-	mod->cfi_check = (cfi_check_fn)
-		find_kallsyms_symbol_value(mod, "__cfi_check");
-	init = (initcall_t *)
-		find_kallsyms_symbol_value(mod, "__cfi_jt_init_module");
-	/* Fix init/exit functions to point to the CFI jump table */
-	if (init)
-		mod->init = *init;
-#ifdef CONFIG_MODULE_UNLOAD
-	exit = (exitcall_t *)
-		find_kallsyms_symbol_value(mod, "__cfi_jt_cleanup_module");
-	if (exit)
-		mod->exit = *exit;
-#endif
-	rcu_read_unlock_sched();
-
-	cfi_module_add(mod, mod_tree.addr_min);
-#endif
-}
-
-static void cfi_cleanup(struct module *mod)
-{
-#ifdef CONFIG_CFI_CLANG
-	cfi_module_remove(mod, mod_tree.addr_min);
-#endif
-}
-
 /* Keep in sync with MODULE_FLAGS_BUF_SIZE !!! */
 char *module_flags(struct module *mod, char *buf, bool show_state)
 {
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 39060a5d0905..7cd5f5e7e0a1 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1651,7 +1651,7 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
 	struct work_struct *work = &dwork->work;
 
 	WARN_ON_ONCE(!wq);
-	WARN_ON_FUNCTION_MISMATCH(timer->function, delayed_work_timer_fn);
+	WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
 	WARN_ON_ONCE(timer_pending(timer));
 	WARN_ON_ONCE(!list_empty(&work->entry));