--- /dev/null
+/*
+ * CFI (Control Flow Integrity) error and slowpath handling
+ *
+ * Copyright (C) 2017 Google, Inc.
+ */
+
+#include <linux/gfp.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/ratelimit.h>
+#include <linux/rcupdate.h>
+#include <linux/spinlock.h>
+#include <asm/bug.h>
+#include <asm/cacheflush.h>
+#include <asm/memory.h>
+#include <asm/set_memory.h>
+
+/* Compiler-defined handler names */
+#ifdef CONFIG_CFI_PERMISSIVE
+#define cfi_failure_handler __ubsan_handle_cfi_check_fail
+#define cfi_slowpath_handler __cfi_slowpath_diag
+#else /* enforcing */
+#define cfi_failure_handler __ubsan_handle_cfi_check_fail_abort
+#define cfi_slowpath_handler __cfi_slowpath
+#endif /* CONFIG_CFI_PERMISSIVE */
+
+static inline void handle_cfi_failure()
+{
+#ifdef CONFIG_CFI_PERMISSIVE
+ WARN_RATELIMIT(1, "CFI failure:\n");
+#else
+ pr_err("CFI failure:\n");
+ BUG();
+#endif
+}
+
+#ifdef CONFIG_MODULES
+#ifdef CONFIG_CFI_CLANG_SHADOW
+struct shadow_range {
+ /* Module address range */
+ unsigned long mod_min_addr;
+ unsigned long mod_max_addr;
+ /* Module page range */
+ unsigned long min_page;
+ unsigned long max_page;
+};
+
+#define SHADOW_ORDER 1
+#define SHADOW_PAGES (1 << SHADOW_ORDER)
+#define SHADOW_SIZE \
+ ((SHADOW_PAGES * PAGE_SIZE - sizeof(struct shadow_range)) / sizeof(u16))
+#define SHADOW_INVALID 0xFFFF
+
+struct cfi_shadow {
+ /* Page range covered by the shadow */
+ struct shadow_range r;
+ /* Page offsets to __cfi_check functions in modules */
+ u16 shadow[SHADOW_SIZE];
+};
+
+static DEFINE_SPINLOCK(shadow_update_lock);
+static struct cfi_shadow __rcu *cfi_shadow __read_mostly = NULL;
+
+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->r.min_page))
+ return -1; /* Outside of module area */
+
+ index = page - s->r.min_page;
+
+ if (index >= SHADOW_SIZE)
+ return -1; /* Cannot be addressed with shadow */
+
+ return (int)index;
+}
+
+static inline unsigned long shadow_to_ptr(const struct cfi_shadow *s,
+ int index)
+{
+ BUG_ON(index < 0 || index >= SHADOW_SIZE);
+
+ if (unlikely(s->shadow[index] == SHADOW_INVALID))
+ return 0;
+
+ return (s->r.min_page + 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, sizeof(next->shadow));
+
+ if (!prev)
+ return; /* No previous shadow */
+
+ /* If the base address didn't change, update is not needed */
+ if (prev->r.min_page == next->r.min_page) {
+ memcpy(next->shadow, prev->shadow, sizeof(next->shadow));
+ return;
+ }
+
+ /* Convert the previous shadow to the new address range */
+ for (i = 0; i < SHADOW_SIZE; ++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_ptr(prev, prev->shadow[i]));
+ if (check < 0)
+ continue;
+
+ next->shadow[index] = (u16)check;
+ }
+}
+
+static void add_module_to_shadow(struct cfi_shadow *s, struct module *mod)
+{
+ unsigned long ptr;
+ unsigned long min_page_addr;
+ unsigned long max_page_addr;
+ unsigned long check = (unsigned long)mod->cfi_check;
+ int check_index = ptr_to_shadow(s, check);
+
+ BUG_ON((check & PAGE_MASK) != check); /* Must be page aligned */
+
+ if (check_index < 0)
+ return; /* Module not addressable with shadow */
+
+ min_page_addr = (unsigned long)mod->core_layout.base & PAGE_MASK;
+ max_page_addr = (unsigned long)mod->core_layout.base +
+ mod->core_layout.text_size;
+ max_page_addr &= PAGE_MASK;
+
+ /* For each page, store the check function index in the shadow */
+ for (ptr = min_page_addr; ptr <= max_page_addr; ptr += PAGE_SIZE) {
+ int index = ptr_to_shadow(s, ptr);
+ if (index >= 0) {
+ /* Assume a page only contains code for one module */
+ BUG_ON(s->shadow[index] != SHADOW_INVALID);
+ s->shadow[index] = (u16)check_index;
+ }
+ }
+}
+
+static void remove_module_from_shadow(struct cfi_shadow *s, struct module *mod)
+{
+ unsigned long ptr;
+ unsigned long min_page_addr;
+ unsigned long max_page_addr;
+
+ min_page_addr = (unsigned long)mod->core_layout.base & PAGE_MASK;
+ max_page_addr = (unsigned long)mod->core_layout.base +
+ mod->core_layout.text_size;
+ max_page_addr &= PAGE_MASK;
+
+ for (ptr = min_page_addr; ptr <= max_page_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 *);
+
+static void update_shadow(struct module *mod, unsigned long min_addr,
+ unsigned long max_addr, update_shadow_fn fn)
+{
+ struct cfi_shadow *prev;
+ struct cfi_shadow *next = (struct cfi_shadow *)
+ __get_free_pages(GFP_KERNEL, SHADOW_ORDER);
+
+ BUG_ON(!next);
+
+ next->r.mod_min_addr = min_addr;
+ next->r.mod_max_addr = max_addr;
+ next->r.min_page = min_addr >> PAGE_SHIFT;
+ next->r.max_page = max_addr >> PAGE_SHIFT;
+
+ spin_lock(&shadow_update_lock);
+ prev = rcu_dereference_protected(cfi_shadow, 1);
+ prepare_next_shadow(prev, next);
+
+ fn(next, mod);
+ set_memory_ro((unsigned long)next, SHADOW_PAGES);
+ rcu_assign_pointer(cfi_shadow, next);
+
+ spin_unlock(&shadow_update_lock);
+ synchronize_rcu();
+
+ if (prev) {
+ set_memory_rw((unsigned long)prev, SHADOW_PAGES);
+ free_pages((unsigned long)prev, SHADOW_ORDER);
+ }
+}
+
+void cfi_module_add(struct module *mod, unsigned long min_addr,
+ unsigned long max_addr)
+{
+ update_shadow(mod, min_addr, max_addr, add_module_to_shadow);
+}
+EXPORT_SYMBOL(cfi_module_add);
+
+void cfi_module_remove(struct module *mod, unsigned long min_addr,
+ unsigned long max_addr)
+{
+ update_shadow(mod, min_addr, max_addr, remove_module_from_shadow);
+}
+EXPORT_SYMBOL(cfi_module_remove);
+
+static inline cfi_check_fn ptr_to_check_fn(const struct cfi_shadow __rcu *s,
+ unsigned long ptr)
+{
+ int index;
+ unsigned long check;
+
+ if (unlikely(!s))
+ return NULL; /* No shadow available */
+
+ if (ptr < s->r.mod_min_addr || ptr > s->r.mod_max_addr)
+ return NULL; /* Not in a mapped module */
+
+ index = ptr_to_shadow(s, ptr);
+ if (index < 0)
+ return NULL; /* Cannot be addressed with shadow */
+
+ return (cfi_check_fn)shadow_to_ptr(s, index);
+}
+#endif /* CONFIG_CFI_CLANG_SHADOW */
+
+static inline cfi_check_fn find_module_cfi_check(void *ptr)
+{
+ struct module *mod;
+
+ preempt_disable();
+ mod = __module_address((unsigned long)ptr);
+ preempt_enable();
+
+ if (mod)
+ return mod->cfi_check;
+
+ return CFI_CHECK_FN;
+}
+
+static inline cfi_check_fn find_cfi_check(void *ptr)
+{
+#ifdef CONFIG_CFI_CLANG_SHADOW
+ cfi_check_fn f;
+
+ if (!rcu_access_pointer(cfi_shadow))
+ return CFI_CHECK_FN; /* No loaded modules */
+
+ /* Look up the __cfi_check function to use */
+ rcu_read_lock();
+ f = ptr_to_check_fn(rcu_dereference(cfi_shadow), (unsigned long)ptr);
+ rcu_read_unlock();
+
+ if (f)
+ return f;
+
+ /*
+ * Fall back to find_module_cfi_check, which works also for a larger
+ * module address space, but is slower.
+ */
+#endif /* CONFIG_CFI_CLANG_SHADOW */
+
+ return find_module_cfi_check(ptr);
+}
+
+void cfi_slowpath_handler(uint64_t id, void *ptr, void *diag)
+{
+ cfi_check_fn check = find_cfi_check(ptr);
+
+ if (likely(check))
+ check(id, ptr, diag);
+ else /* Don't allow unchecked modules */
+ handle_cfi_failure();
+}
+EXPORT_SYMBOL(cfi_slowpath_handler);
+#endif /* CONFIG_MODULES */
+
+void cfi_failure_handler(void *data, void *value, void *vtable)
+{
+ handle_cfi_failure();
+}
+EXPORT_SYMBOL(cfi_failure_handler);
+
+void __cfi_check_fail(void *data, void *value)
+{
+ handle_cfi_failure();
+}
projects / GitHub / moto-9609 / android_kernel_motorola_exynos9610.git / commitdiff