| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * core.c - Kernel Live Patching Core |
| * |
| * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> |
| * Copyright (C) 2014 SUSE |
| */ |
| |
| #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| |
| #include <linux/module.h> |
| #include <linux/kernel.h> |
| #include <linux/mutex.h> |
| #include <linux/slab.h> |
| #include <linux/list.h> |
| #include <linux/kallsyms.h> |
| #include <linux/livepatch.h> |
| #include <linux/elf.h> |
| #include <linux/moduleloader.h> |
| #include <linux/completion.h> |
| #include <linux/memory.h> |
| #include <linux/rcupdate.h> |
| #include <asm/cacheflush.h> |
| #include "core.h" |
| #include "patch.h" |
| #include "state.h" |
| #include "transition.h" |
| |
| /* |
| * klp_mutex is a coarse lock which serializes access to klp data. All |
| * accesses to klp-related variables and structures must have mutex protection, |
| * except within the following functions which carefully avoid the need for it: |
| * |
| * - klp_ftrace_handler() |
| * - klp_update_patch_state() |
| */ |
| DEFINE_MUTEX(klp_mutex); |
| |
| /* |
| * Actively used patches: enabled or in transition. Note that replaced |
| * or disabled patches are not listed even though the related kernel |
| * module still can be loaded. |
| */ |
| LIST_HEAD(klp_patches); |
| |
| static struct kobject *klp_root_kobj; |
| |
| static bool klp_is_module(struct klp_object *obj) |
| { |
| return obj->name; |
| } |
| |
| /* sets obj->mod if object is not vmlinux and module is found */ |
| static void klp_find_object_module(struct klp_object *obj) |
| { |
| struct module *mod; |
| |
| if (!klp_is_module(obj)) |
| return; |
| |
| rcu_read_lock_sched(); |
| /* |
| * We do not want to block removal of patched modules and therefore |
| * we do not take a reference here. The patches are removed by |
| * klp_module_going() instead. |
| */ |
| mod = find_module(obj->name); |
| /* |
| * Do not mess work of klp_module_coming() and klp_module_going(). |
| * Note that the patch might still be needed before klp_module_going() |
| * is called. Module functions can be called even in the GOING state |
| * until mod->exit() finishes. This is especially important for |
| * patches that modify semantic of the functions. |
| */ |
| if (mod && mod->klp_alive) |
| obj->mod = mod; |
| |
| rcu_read_unlock_sched(); |
| } |
| |
| static bool klp_initialized(void) |
| { |
| return !!klp_root_kobj; |
| } |
| |
| static struct klp_func *klp_find_func(struct klp_object *obj, |
| struct klp_func *old_func) |
| { |
| struct klp_func *func; |
| |
| klp_for_each_func(obj, func) { |
| if ((strcmp(old_func->old_name, func->old_name) == 0) && |
| (old_func->old_sympos == func->old_sympos)) { |
| return func; |
| } |
| } |
| |
| return NULL; |
| } |
| |
| static struct klp_object *klp_find_object(struct klp_patch *patch, |
| struct klp_object *old_obj) |
| { |
| struct klp_object *obj; |
| |
| klp_for_each_object(patch, obj) { |
| if (klp_is_module(old_obj)) { |
| if (klp_is_module(obj) && |
| strcmp(old_obj->name, obj->name) == 0) { |
| return obj; |
| } |
| } else if (!klp_is_module(obj)) { |
| return obj; |
| } |
| } |
| |
| return NULL; |
| } |
| |
| struct klp_find_arg { |
| const char *objname; |
| const char *name; |
| unsigned long addr; |
| unsigned long count; |
| unsigned long pos; |
| }; |
| |
| static int klp_find_callback(void *data, const char *name, |
| struct module *mod, unsigned long addr) |
| { |
| struct klp_find_arg *args = data; |
| |
| if ((mod && !args->objname) || (!mod && args->objname)) |
| return 0; |
| |
| if (strcmp(args->name, name)) |
| return 0; |
| |
| if (args->objname && strcmp(args->objname, mod->name)) |
| return 0; |
| |
| args->addr = addr; |
| args->count++; |
| |
| /* |
| * Finish the search when the symbol is found for the desired position |
| * or the position is not defined for a non-unique symbol. |
| */ |
| if ((args->pos && (args->count == args->pos)) || |
| (!args->pos && (args->count > 1))) |
| return 1; |
| |
| return 0; |
| } |
| |
| static int klp_find_object_symbol(const char *objname, const char *name, |
| unsigned long sympos, unsigned long *addr) |
| { |
| struct klp_find_arg args = { |
| .objname = objname, |
| .name = name, |
| .addr = 0, |
| .count = 0, |
| .pos = sympos, |
| }; |
| |
| if (objname) |
| module_kallsyms_on_each_symbol(klp_find_callback, &args); |
| else |
| kallsyms_on_each_symbol(klp_find_callback, &args); |
| |
| /* |
| * Ensure an address was found. If sympos is 0, ensure symbol is unique; |
| * otherwise ensure the symbol position count matches sympos. |
| */ |
| if (args.addr == 0) |
| pr_err("symbol '%s' not found in symbol table\n", name); |
| else if (args.count > 1 && sympos == 0) { |
| pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n", |
| name, objname); |
| } else if (sympos != args.count && sympos > 0) { |
| pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n", |
| sympos, name, objname ? objname : "vmlinux"); |
| } else { |
| *addr = args.addr; |
| return 0; |
| } |
| |
| *addr = 0; |
| return -EINVAL; |
| } |
| |
| static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab, |
| unsigned int symndx, Elf_Shdr *relasec, |
| const char *sec_objname) |
| { |
| int i, cnt, ret; |
| char sym_objname[MODULE_NAME_LEN]; |
| char sym_name[KSYM_NAME_LEN]; |
| Elf_Rela *relas; |
| Elf_Sym *sym; |
| unsigned long sympos, addr; |
| bool sym_vmlinux; |
| bool sec_vmlinux = !strcmp(sec_objname, "vmlinux"); |
| |
| /* |
| * Since the field widths for sym_objname and sym_name in the sscanf() |
| * call are hard-coded and correspond to MODULE_NAME_LEN and |
| * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN |
| * and KSYM_NAME_LEN have the values we expect them to have. |
| * |
| * Because the value of MODULE_NAME_LEN can differ among architectures, |
| * we use the smallest/strictest upper bound possible (56, based on |
| * the current definition of MODULE_NAME_LEN) to prevent overflows. |
| */ |
| BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128); |
| |
| relas = (Elf_Rela *) relasec->sh_addr; |
| /* For each rela in this klp relocation section */ |
| for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) { |
| sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info); |
| if (sym->st_shndx != SHN_LIVEPATCH) { |
| pr_err("symbol %s is not marked as a livepatch symbol\n", |
| strtab + sym->st_name); |
| return -EINVAL; |
| } |
| |
| /* Format: .klp.sym.sym_objname.sym_name,sympos */ |
| cnt = sscanf(strtab + sym->st_name, |
| ".klp.sym.%55[^.].%127[^,],%lu", |
| sym_objname, sym_name, &sympos); |
| if (cnt != 3) { |
| pr_err("symbol %s has an incorrectly formatted name\n", |
| strtab + sym->st_name); |
| return -EINVAL; |
| } |
| |
| sym_vmlinux = !strcmp(sym_objname, "vmlinux"); |
| |
| /* |
| * Prevent module-specific KLP rela sections from referencing |
| * vmlinux symbols. This helps prevent ordering issues with |
| * module special section initializations. Presumably such |
| * symbols are exported and normal relas can be used instead. |
| */ |
| if (!sec_vmlinux && sym_vmlinux) { |
| pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section", |
| sym_name); |
| return -EINVAL; |
| } |
| |
| /* klp_find_object_symbol() treats a NULL objname as vmlinux */ |
| ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname, |
| sym_name, sympos, &addr); |
| if (ret) |
| return ret; |
| |
| sym->st_value = addr; |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * At a high-level, there are two types of klp relocation sections: those which |
| * reference symbols which live in vmlinux; and those which reference symbols |
| * which live in other modules. This function is called for both types: |
| * |
| * 1) When a klp module itself loads, the module code calls this function to |
| * write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections). |
| * These relocations are written to the klp module text to allow the patched |
| * code/data to reference unexported vmlinux symbols. They're written as |
| * early as possible to ensure that other module init code (.e.g., |
| * jump_label_apply_nops) can access any unexported vmlinux symbols which |
| * might be referenced by the klp module's special sections. |
| * |
| * 2) When a to-be-patched module loads -- or is already loaded when a |
| * corresponding klp module loads -- klp code calls this function to write |
| * module-specific klp relocations (.klp.rela.{module}.* sections). These |
| * are written to the klp module text to allow the patched code/data to |
| * reference symbols which live in the to-be-patched module or one of its |
| * module dependencies. Exported symbols are supported, in addition to |
| * unexported symbols, in order to enable late module patching, which allows |
| * the to-be-patched module to be loaded and patched sometime *after* the |
| * klp module is loaded. |
| */ |
| int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, |
| const char *shstrtab, const char *strtab, |
| unsigned int symndx, unsigned int secndx, |
| const char *objname) |
| { |
| int cnt, ret; |
| char sec_objname[MODULE_NAME_LEN]; |
| Elf_Shdr *sec = sechdrs + secndx; |
| |
| /* |
| * Format: .klp.rela.sec_objname.section_name |
| * See comment in klp_resolve_symbols() for an explanation |
| * of the selected field width value. |
| */ |
| cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]", |
| sec_objname); |
| if (cnt != 1) { |
| pr_err("section %s has an incorrectly formatted name\n", |
| shstrtab + sec->sh_name); |
| return -EINVAL; |
| } |
| |
| if (strcmp(objname ? objname : "vmlinux", sec_objname)) |
| return 0; |
| |
| ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname); |
| if (ret) |
| return ret; |
| |
| return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod); |
| } |
| |
| /* |
| * Sysfs Interface |
| * |
| * /sys/kernel/livepatch |
| * /sys/kernel/livepatch/<patch> |
| * /sys/kernel/livepatch/<patch>/enabled |
| * /sys/kernel/livepatch/<patch>/transition |
| * /sys/kernel/livepatch/<patch>/force |
| * /sys/kernel/livepatch/<patch>/<object> |
| * /sys/kernel/livepatch/<patch>/<object>/patched |
| * /sys/kernel/livepatch/<patch>/<object>/<function,sympos> |
| */ |
| static int __klp_disable_patch(struct klp_patch *patch); |
| |
| static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, |
| const char *buf, size_t count) |
| { |
| struct klp_patch *patch; |
| int ret; |
| bool enabled; |
| |
| ret = kstrtobool(buf, &enabled); |
| if (ret) |
| return ret; |
| |
| patch = container_of(kobj, struct klp_patch, kobj); |
| |
| mutex_lock(&klp_mutex); |
| |
| if (patch->enabled == enabled) { |
| /* already in requested state */ |
| ret = -EINVAL; |
| goto out; |
| } |
| |
| /* |
| * Allow to reverse a pending transition in both ways. It might be |
| * necessary to complete the transition without forcing and breaking |
| * the system integrity. |
| * |
| * Do not allow to re-enable a disabled patch. |
| */ |
| if (patch == klp_transition_patch) |
| klp_reverse_transition(); |
| else if (!enabled) |
| ret = __klp_disable_patch(patch); |
| else |
| ret = -EINVAL; |
| |
| out: |
| mutex_unlock(&klp_mutex); |
| |
| if (ret) |
| return ret; |
| return count; |
| } |
| |
| static ssize_t enabled_show(struct kobject *kobj, |
| struct kobj_attribute *attr, char *buf) |
| { |
| struct klp_patch *patch; |
| |
| patch = container_of(kobj, struct klp_patch, kobj); |
| return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled); |
| } |
| |
| static ssize_t transition_show(struct kobject *kobj, |
| struct kobj_attribute *attr, char *buf) |
| { |
| struct klp_patch *patch; |
| |
| patch = container_of(kobj, struct klp_patch, kobj); |
| return snprintf(buf, PAGE_SIZE-1, "%d\n", |
| patch == klp_transition_patch); |
| } |
| |
| static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr, |
| const char *buf, size_t count) |
| { |
| struct klp_patch *patch; |
| int ret; |
| bool val; |
| |
| ret = kstrtobool(buf, &val); |
| if (ret) |
| return ret; |
| |
| if (!val) |
| return count; |
| |
| mutex_lock(&klp_mutex); |
| |
| patch = container_of(kobj, struct klp_patch, kobj); |
| if (patch != klp_transition_patch) { |
| mutex_unlock(&klp_mutex); |
| return -EINVAL; |
| } |
| |
| klp_force_transition(); |
| |
| mutex_unlock(&klp_mutex); |
| |
| return count; |
| } |
| |
| static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled); |
| static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition); |
| static struct kobj_attribute force_kobj_attr = __ATTR_WO(force); |
| static struct attribute *klp_patch_attrs[] = { |
| &enabled_kobj_attr.attr, |
| &transition_kobj_attr.attr, |
| &force_kobj_attr.attr, |
| NULL |
| }; |
| ATTRIBUTE_GROUPS(klp_patch); |
| |
| static ssize_t patched_show(struct kobject *kobj, |
| struct kobj_attribute *attr, char *buf) |
| { |
| struct klp_object *obj; |
| |
| obj = container_of(kobj, struct klp_object, kobj); |
| return sysfs_emit(buf, "%d\n", obj->patched); |
| } |
| |
| static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched); |
| static struct attribute *klp_object_attrs[] = { |
| &patched_kobj_attr.attr, |
| NULL, |
| }; |
| ATTRIBUTE_GROUPS(klp_object); |
| |
| static void klp_free_object_dynamic(struct klp_object *obj) |
| { |
| kfree(obj->name); |
| kfree(obj); |
| } |
| |
| static void klp_init_func_early(struct klp_object *obj, |
| struct klp_func *func); |
| static void klp_init_object_early(struct klp_patch *patch, |
| struct klp_object *obj); |
| |
| static struct klp_object *klp_alloc_object_dynamic(const char *name, |
| struct klp_patch *patch) |
| { |
| struct klp_object *obj; |
| |
| obj = kzalloc(sizeof(*obj), GFP_KERNEL); |
| if (!obj) |
| return NULL; |
| |
| if (name) { |
| obj->name = kstrdup(name, GFP_KERNEL); |
| if (!obj->name) { |
| kfree(obj); |
| return NULL; |
| } |
| } |
| |
| klp_init_object_early(patch, obj); |
| obj->dynamic = true; |
| |
| return obj; |
| } |
| |
| static void klp_free_func_nop(struct klp_func *func) |
| { |
| kfree(func->old_name); |
| kfree(func); |
| } |
| |
| static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func, |
| struct klp_object *obj) |
| { |
| struct klp_func *func; |
| |
| func = kzalloc(sizeof(*func), GFP_KERNEL); |
| if (!func) |
| return NULL; |
| |
| if (old_func->old_name) { |
| func->old_name = kstrdup(old_func->old_name, GFP_KERNEL); |
| if (!func->old_name) { |
| kfree(func); |
| return NULL; |
| } |
| } |
| |
| klp_init_func_early(obj, func); |
| /* |
| * func->new_func is same as func->old_func. These addresses are |
| * set when the object is loaded, see klp_init_object_loaded(). |
| */ |
| func->old_sympos = old_func->old_sympos; |
| func->nop = true; |
| |
| return func; |
| } |
| |
| static int klp_add_object_nops(struct klp_patch *patch, |
| struct klp_object *old_obj) |
| { |
| struct klp_object *obj; |
| struct klp_func *func, *old_func; |
| |
| obj = klp_find_object(patch, old_obj); |
| |
| if (!obj) { |
| obj = klp_alloc_object_dynamic(old_obj->name, patch); |
| if (!obj) |
| return -ENOMEM; |
| } |
| |
| klp_for_each_func(old_obj, old_func) { |
| func = klp_find_func(obj, old_func); |
| if (func) |
| continue; |
| |
| func = klp_alloc_func_nop(old_func, obj); |
| if (!func) |
| return -ENOMEM; |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * Add 'nop' functions which simply return to the caller to run |
| * the original function. The 'nop' functions are added to a |
| * patch to facilitate a 'replace' mode. |
| */ |
| static int klp_add_nops(struct klp_patch *patch) |
| { |
| struct klp_patch *old_patch; |
| struct klp_object *old_obj; |
| |
| klp_for_each_patch(old_patch) { |
| klp_for_each_object(old_patch, old_obj) { |
| int err; |
| |
| err = klp_add_object_nops(patch, old_obj); |
| if (err) |
| return err; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static void klp_kobj_release_patch(struct kobject *kobj) |
| { |
| struct klp_patch *patch; |
| |
| patch = container_of(kobj, struct klp_patch, kobj); |
| complete(&patch->finish); |
| } |
| |
| static struct kobj_type klp_ktype_patch = { |
| .release = klp_kobj_release_patch, |
| .sysfs_ops = &kobj_sysfs_ops, |
| .default_groups = klp_patch_groups, |
| }; |
| |
| static void klp_kobj_release_object(struct kobject *kobj) |
| { |
| struct klp_object *obj; |
| |
| obj = container_of(kobj, struct klp_object, kobj); |
| |
| if (obj->dynamic) |
| klp_free_object_dynamic(obj); |
| } |
| |
| static struct kobj_type klp_ktype_object = { |
| .release = klp_kobj_release_object, |
| .sysfs_ops = &kobj_sysfs_ops, |
| .default_groups = klp_object_groups, |
| }; |
| |
| static void klp_kobj_release_func(struct kobject *kobj) |
| { |
| struct klp_func *func; |
| |
| func = container_of(kobj, struct klp_func, kobj); |
| |
| if (func->nop) |
| klp_free_func_nop(func); |
| } |
| |
| static struct kobj_type klp_ktype_func = { |
| .release = klp_kobj_release_func, |
| .sysfs_ops = &kobj_sysfs_ops, |
| }; |
| |
| static void __klp_free_funcs(struct klp_object *obj, bool nops_only) |
| { |
| struct klp_func *func, *tmp_func; |
| |
| klp_for_each_func_safe(obj, func, tmp_func) { |
| if (nops_only && !func->nop) |
| continue; |
| |
| list_del(&func->node); |
| kobject_put(&func->kobj); |
| } |
| } |
| |
| /* Clean up when a patched object is unloaded */ |
| static void klp_free_object_loaded(struct klp_object *obj) |
| { |
| struct klp_func *func; |
| |
| obj->mod = NULL; |
| |
| klp_for_each_func(obj, func) { |
| func->old_func = NULL; |
| |
| if (func->nop) |
| func->new_func = NULL; |
| } |
| } |
| |
| static void __klp_free_objects(struct klp_patch *patch, bool nops_only) |
| { |
| struct klp_object *obj, *tmp_obj; |
| |
| klp_for_each_object_safe(patch, obj, tmp_obj) { |
| __klp_free_funcs(obj, nops_only); |
| |
| if (nops_only && !obj->dynamic) |
| continue; |
| |
| list_del(&obj->node); |
| kobject_put(&obj->kobj); |
| } |
| } |
| |
| static void klp_free_objects(struct klp_patch *patch) |
| { |
| __klp_free_objects(patch, false); |
| } |
| |
| static void klp_free_objects_dynamic(struct klp_patch *patch) |
| { |
| __klp_free_objects(patch, true); |
| } |
| |
| /* |
| * This function implements the free operations that can be called safely |
| * under klp_mutex. |
| * |
| * The operation must be completed by calling klp_free_patch_finish() |
| * outside klp_mutex. |
| */ |
| static void klp_free_patch_start(struct klp_patch *patch) |
| { |
| if (!list_empty(&patch->list)) |
| list_del(&patch->list); |
| |
| klp_free_objects(patch); |
| } |
| |
| /* |
| * This function implements the free part that must be called outside |
| * klp_mutex. |
| * |
| * It must be called after klp_free_patch_start(). And it has to be |
| * the last function accessing the livepatch structures when the patch |
| * gets disabled. |
| */ |
| static void klp_free_patch_finish(struct klp_patch *patch) |
| { |
| /* |
| * Avoid deadlock with enabled_store() sysfs callback by |
| * calling this outside klp_mutex. It is safe because |
| * this is called when the patch gets disabled and it |
| * cannot get enabled again. |
| */ |
| kobject_put(&patch->kobj); |
| wait_for_completion(&patch->finish); |
| |
| /* Put the module after the last access to struct klp_patch. */ |
| if (!patch->forced) |
| module_put(patch->mod); |
| } |
| |
| /* |
| * The livepatch might be freed from sysfs interface created by the patch. |
| * This work allows to wait until the interface is destroyed in a separate |
| * context. |
| */ |
| static void klp_free_patch_work_fn(struct work_struct *work) |
| { |
| struct klp_patch *patch = |
| container_of(work, struct klp_patch, free_work); |
| |
| klp_free_patch_finish(patch); |
| } |
| |
| void klp_free_patch_async(struct klp_patch *patch) |
| { |
| klp_free_patch_start(patch); |
| schedule_work(&patch->free_work); |
| } |
| |
| void klp_free_replaced_patches_async(struct klp_patch *new_patch) |
| { |
| struct klp_patch *old_patch, *tmp_patch; |
| |
| klp_for_each_patch_safe(old_patch, tmp_patch) { |
| if (old_patch == new_patch) |
| return; |
| klp_free_patch_async(old_patch); |
| } |
| } |
| |
| static int klp_init_func(struct klp_object *obj, struct klp_func *func) |
| { |
| if (!func->old_name) |
| return -EINVAL; |
| |
| /* |
| * NOPs get the address later. The patched module must be loaded, |
| * see klp_init_object_loaded(). |
| */ |
| if (!func->new_func && !func->nop) |
| return -EINVAL; |
| |
| if (strlen(func->old_name) >= KSYM_NAME_LEN) |
| return -EINVAL; |
| |
| INIT_LIST_HEAD(&func->stack_node); |
| func->patched = false; |
| func->transition = false; |
| |
| /* The format for the sysfs directory is <function,sympos> where sympos |
| * is the nth occurrence of this symbol in kallsyms for the patched |
| * object. If the user selects 0 for old_sympos, then 1 will be used |
| * since a unique symbol will be the first occurrence. |
| */ |
| return kobject_add(&func->kobj, &obj->kobj, "%s,%lu", |
| func->old_name, |
| func->old_sympos ? func->old_sympos : 1); |
| } |
| |
| static int klp_apply_object_relocs(struct klp_patch *patch, |
| struct klp_object *obj) |
| { |
| int i, ret; |
| struct klp_modinfo *info = patch->mod->klp_info; |
| |
| for (i = 1; i < info->hdr.e_shnum; i++) { |
| Elf_Shdr *sec = info->sechdrs + i; |
| |
| if (!(sec->sh_flags & SHF_RELA_LIVEPATCH)) |
| continue; |
| |
| ret = klp_apply_section_relocs(patch->mod, info->sechdrs, |
| info->secstrings, |
| patch->mod->core_kallsyms.strtab, |
| info->symndx, i, obj->name); |
| if (ret) |
| return ret; |
| } |
| |
| return 0; |
| } |
| |
| /* parts of the initialization that is done only when the object is loaded */ |
| static int klp_init_object_loaded(struct klp_patch *patch, |
| struct klp_object *obj) |
| { |
| struct klp_func *func; |
| int ret; |
| |
| if (klp_is_module(obj)) { |
| /* |
| * Only write module-specific relocations here |
| * (.klp.rela.{module}.*). vmlinux-specific relocations were |
| * written earlier during the initialization of the klp module |
| * itself. |
| */ |
| ret = klp_apply_object_relocs(patch, obj); |
| if (ret) |
| return ret; |
| } |
| |
| klp_for_each_func(obj, func) { |
| ret = klp_find_object_symbol(obj->name, func->old_name, |
| func->old_sympos, |
| (unsigned long *)&func->old_func); |
| if (ret) |
| return ret; |
| |
| ret = kallsyms_lookup_size_offset((unsigned long)func->old_func, |
| &func->old_size, NULL); |
| if (!ret) { |
| pr_err("kallsyms size lookup failed for '%s'\n", |
| func->old_name); |
| return -ENOENT; |
| } |
| |
| if (func->nop) |
| func->new_func = func->old_func; |
| |
| ret = kallsyms_lookup_size_offset((unsigned long)func->new_func, |
| &func->new_size, NULL); |
| if (!ret) { |
| pr_err("kallsyms size lookup failed for '%s' replacement\n", |
| func->old_name); |
| return -ENOENT; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) |
| { |
| struct klp_func *func; |
| int ret; |
| const char *name; |
| |
| if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN) |
| return -EINVAL; |
| |
| obj->patched = false; |
| obj->mod = NULL; |
| |
| klp_find_object_module(obj); |
| |
| name = klp_is_module(obj) ? obj->name : "vmlinux"; |
| ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name); |
| if (ret) |
| return ret; |
| |
| klp_for_each_func(obj, func) { |
| ret = klp_init_func(obj, func); |
| if (ret) |
| return ret; |
| } |
| |
| if (klp_is_object_loaded(obj)) |
| ret = klp_init_object_loaded(patch, obj); |
| |
| return ret; |
| } |
| |
| static void klp_init_func_early(struct klp_object *obj, |
| struct klp_func *func) |
| { |
| kobject_init(&func->kobj, &klp_ktype_func); |
| list_add_tail(&func->node, &obj->func_list); |
| } |
| |
| static void klp_init_object_early(struct klp_patch *patch, |
| struct klp_object *obj) |
| { |
| INIT_LIST_HEAD(&obj->func_list); |
| kobject_init(&obj->kobj, &klp_ktype_object); |
| list_add_tail(&obj->node, &patch->obj_list); |
| } |
| |
| static void klp_init_patch_early(struct klp_patch *patch) |
| { |
| struct klp_object *obj; |
| struct klp_func *func; |
| |
| INIT_LIST_HEAD(&patch->list); |
| INIT_LIST_HEAD(&patch->obj_list); |
| kobject_init(&patch->kobj, &klp_ktype_patch); |
| patch->enabled = false; |
| patch->forced = false; |
| INIT_WORK(&patch->free_work, klp_free_patch_work_fn); |
| init_completion(&patch->finish); |
| |
| klp_for_each_object_static(patch, obj) { |
| klp_init_object_early(patch, obj); |
| |
| klp_for_each_func_static(obj, func) { |
| klp_init_func_early(obj, func); |
| } |
| } |
| } |
| |
| static int klp_init_patch(struct klp_patch *patch) |
| { |
| struct klp_object *obj; |
| int ret; |
| |
| ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name); |
| if (ret) |
| return ret; |
| |
| if (patch->replace) { |
| ret = klp_add_nops(patch); |
| if (ret) |
| return ret; |
| } |
| |
| klp_for_each_object(patch, obj) { |
| ret = klp_init_object(patch, obj); |
| if (ret) |
| return ret; |
| } |
| |
| list_add_tail(&patch->list, &klp_patches); |
| |
| return 0; |
| } |
| |
| static int __klp_disable_patch(struct klp_patch *patch) |
| { |
| struct klp_object *obj; |
| |
| if (WARN_ON(!patch->enabled)) |
| return -EINVAL; |
| |
| if (klp_transition_patch) |
| return -EBUSY; |
| |
| klp_init_transition(patch, KLP_UNPATCHED); |
| |
| klp_for_each_object(patch, obj) |
| if (obj->patched) |
| klp_pre_unpatch_callback(obj); |
| |
| /* |
| * Enforce the order of the func->transition writes in |
| * klp_init_transition() and the TIF_PATCH_PENDING writes in |
| * klp_start_transition(). In the rare case where klp_ftrace_handler() |
| * is called shortly after klp_update_patch_state() switches the task, |
| * this ensures the handler sees that func->transition is set. |
| */ |
| smp_wmb(); |
| |
| klp_start_transition(); |
| patch->enabled = false; |
| klp_try_complete_transition(); |
| |
| return 0; |
| } |
| |
| static int __klp_enable_patch(struct klp_patch *patch) |
| { |
| struct klp_object *obj; |
| int ret; |
| |
| if (klp_transition_patch) |
| return -EBUSY; |
| |
| if (WARN_ON(patch->enabled)) |
| return -EINVAL; |
| |
| pr_notice("enabling patch '%s'\n", patch->mod->name); |
| |
| klp_init_transition(patch, KLP_PATCHED); |
| |
| /* |
| * Enforce the order of the func->transition writes in |
| * klp_init_transition() and the ops->func_stack writes in |
| * klp_patch_object(), so that klp_ftrace_handler() will see the |
| * func->transition updates before the handler is registered and the |
| * new funcs become visible to the handler. |
| */ |
| smp_wmb(); |
| |
| klp_for_each_object(patch, obj) { |
| if (!klp_is_object_loaded(obj)) |
| continue; |
| |
| ret = klp_pre_patch_callback(obj); |
| if (ret) { |
| pr_warn("pre-patch callback failed for object '%s'\n", |
| klp_is_module(obj) ? obj->name : "vmlinux"); |
| goto err; |
| } |
| |
| ret = klp_patch_object(obj); |
| if (ret) { |
| pr_warn("failed to patch object '%s'\n", |
| klp_is_module(obj) ? obj->name : "vmlinux"); |
| goto err; |
| } |
| } |
| |
| klp_start_transition(); |
| patch->enabled = true; |
| klp_try_complete_transition(); |
| |
| return 0; |
| err: |
| pr_warn("failed to enable patch '%s'\n", patch->mod->name); |
| |
| klp_cancel_transition(); |
| return ret; |
| } |
| |
| /** |
| * klp_enable_patch() - enable the livepatch |
| * @patch: patch to be enabled |
| * |
| * Initializes the data structure associated with the patch, creates the sysfs |
| * interface, performs the needed symbol lookups and code relocations, |
| * registers the patched functions with ftrace. |
| * |
| * This function is supposed to be called from the livepatch module_init() |
| * callback. |
| * |
| * Return: 0 on success, otherwise error |
| */ |
| int klp_enable_patch(struct klp_patch *patch) |
| { |
| int ret; |
| struct klp_object *obj; |
| |
| if (!patch || !patch->mod || !patch->objs) |
| return -EINVAL; |
| |
| klp_for_each_object_static(patch, obj) { |
| if (!obj->funcs) |
| return -EINVAL; |
| } |
| |
| |
| if (!is_livepatch_module(patch->mod)) { |
| pr_err("module %s is not marked as a livepatch module\n", |
| patch->mod->name); |
| return -EINVAL; |
| } |
| |
| if (!klp_initialized()) |
| return -ENODEV; |
| |
| if (!klp_have_reliable_stack()) { |
| pr_warn("This architecture doesn't have support for the livepatch consistency model.\n"); |
| pr_warn("The livepatch transition may never complete.\n"); |
| } |
| |
| mutex_lock(&klp_mutex); |
| |
| if (!klp_is_patch_compatible(patch)) { |
| pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n", |
| patch->mod->name); |
| mutex_unlock(&klp_mutex); |
| return -EINVAL; |
| } |
| |
| if (!try_module_get(patch->mod)) { |
| mutex_unlock(&klp_mutex); |
| return -ENODEV; |
| } |
| |
| klp_init_patch_early(patch); |
| |
| ret = klp_init_patch(patch); |
| if (ret) |
| goto err; |
| |
| ret = __klp_enable_patch(patch); |
| if (ret) |
| goto err; |
| |
| mutex_unlock(&klp_mutex); |
| |
| return 0; |
| |
| err: |
| klp_free_patch_start(patch); |
| |
| mutex_unlock(&klp_mutex); |
| |
| klp_free_patch_finish(patch); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(klp_enable_patch); |
| |
| /* |
| * This function unpatches objects from the replaced livepatches. |
| * |
| * We could be pretty aggressive here. It is called in the situation where |
| * these structures are no longer accessed from the ftrace handler. |
| * All functions are redirected by the klp_transition_patch. They |
| * use either a new code or they are in the original code because |
| * of the special nop function patches. |
| * |
| * The only exception is when the transition was forced. In this case, |
| * klp_ftrace_handler() might still see the replaced patch on the stack. |
| * Fortunately, it is carefully designed to work with removed functions |
| * thanks to RCU. We only have to keep the patches on the system. Also |
| * this is handled transparently by patch->module_put. |
| */ |
| void klp_unpatch_replaced_patches(struct klp_patch *new_patch) |
| { |
| struct klp_patch *old_patch; |
| |
| klp_for_each_patch(old_patch) { |
| if (old_patch == new_patch) |
| return; |
| |
| old_patch->enabled = false; |
| klp_unpatch_objects(old_patch); |
| } |
| } |
| |
| /* |
| * This function removes the dynamically allocated 'nop' functions. |
| * |
| * We could be pretty aggressive. NOPs do not change the existing |
| * behavior except for adding unnecessary delay by the ftrace handler. |
| * |
| * It is safe even when the transition was forced. The ftrace handler |
| * will see a valid ops->func_stack entry thanks to RCU. |
| * |
| * We could even free the NOPs structures. They must be the last entry |
| * in ops->func_stack. Therefore unregister_ftrace_function() is called. |
| * It does the same as klp_synchronize_transition() to make sure that |
| * nobody is inside the ftrace handler once the operation finishes. |
| * |
| * IMPORTANT: It must be called right after removing the replaced patches! |
| */ |
| void klp_discard_nops(struct klp_patch *new_patch) |
| { |
| klp_unpatch_objects_dynamic(klp_transition_patch); |
| klp_free_objects_dynamic(klp_transition_patch); |
| } |
| |
| /* |
| * Remove parts of patches that touch a given kernel module. The list of |
| * patches processed might be limited. When limit is NULL, all patches |
| * will be handled. |
| */ |
| static void klp_cleanup_module_patches_limited(struct module *mod, |
| struct klp_patch *limit) |
| { |
| struct klp_patch *patch; |
| struct klp_object *obj; |
| |
| klp_for_each_patch(patch) { |
| if (patch == limit) |
| break; |
| |
| klp_for_each_object(patch, obj) { |
| if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) |
| continue; |
| |
| if (patch != klp_transition_patch) |
| klp_pre_unpatch_callback(obj); |
| |
| pr_notice("reverting patch '%s' on unloading module '%s'\n", |
| patch->mod->name, obj->mod->name); |
| klp_unpatch_object(obj); |
| |
| klp_post_unpatch_callback(obj); |
| |
| klp_free_object_loaded(obj); |
| break; |
| } |
| } |
| } |
| |
| int klp_module_coming(struct module *mod) |
| { |
| int ret; |
| struct klp_patch *patch; |
| struct klp_object *obj; |
| |
| if (WARN_ON(mod->state != MODULE_STATE_COMING)) |
| return -EINVAL; |
| |
| if (!strcmp(mod->name, "vmlinux")) { |
| pr_err("vmlinux.ko: invalid module name"); |
| return -EINVAL; |
| } |
| |
| mutex_lock(&klp_mutex); |
| /* |
| * Each module has to know that klp_module_coming() |
| * has been called. We never know what module will |
| * get patched by a new patch. |
| */ |
| mod->klp_alive = true; |
| |
| klp_for_each_patch(patch) { |
| klp_for_each_object(patch, obj) { |
| if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) |
| continue; |
| |
| obj->mod = mod; |
| |
| ret = klp_init_object_loaded(patch, obj); |
| if (ret) { |
| pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n", |
| patch->mod->name, obj->mod->name, ret); |
| goto err; |
| } |
| |
| pr_notice("applying patch '%s' to loading module '%s'\n", |
| patch->mod->name, obj->mod->name); |
| |
| ret = klp_pre_patch_callback(obj); |
| if (ret) { |
| pr_warn("pre-patch callback failed for object '%s'\n", |
| obj->name); |
| goto err; |
| } |
| |
| ret = klp_patch_object(obj); |
| if (ret) { |
| pr_warn("failed to apply patch '%s' to module '%s' (%d)\n", |
| patch->mod->name, obj->mod->name, ret); |
| |
| klp_post_unpatch_callback(obj); |
| goto err; |
| } |
| |
| if (patch != klp_transition_patch) |
| klp_post_patch_callback(obj); |
| |
| break; |
| } |
| } |
| |
| mutex_unlock(&klp_mutex); |
| |
| return 0; |
| |
| err: |
| /* |
| * If a patch is unsuccessfully applied, return |
| * error to the module loader. |
| */ |
| pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n", |
| patch->mod->name, obj->mod->name, obj->mod->name); |
| mod->klp_alive = false; |
| obj->mod = NULL; |
| klp_cleanup_module_patches_limited(mod, patch); |
| mutex_unlock(&klp_mutex); |
| |
| return ret; |
| } |
| |
| void klp_module_going(struct module *mod) |
| { |
| if (WARN_ON(mod->state != MODULE_STATE_GOING && |
| mod->state != MODULE_STATE_COMING)) |
| return; |
| |
| mutex_lock(&klp_mutex); |
| /* |
| * Each module has to know that klp_module_going() |
| * has been called. We never know what module will |
| * get patched by a new patch. |
| */ |
| mod->klp_alive = false; |
| |
| klp_cleanup_module_patches_limited(mod, NULL); |
| |
| mutex_unlock(&klp_mutex); |
| } |
| |
| static int __init klp_init(void) |
| { |
| klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj); |
| if (!klp_root_kobj) |
| return -ENOMEM; |
| |
| return 0; |
| } |
| |
| module_init(klp_init); |