// SPDX-License-Identifier: GPL-2.0-or-later /* * core.c - Kernel Live Patching Core * * Copyright (C) 2014 Seth Jennings * Copyright (C) 2014 SUSE */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include #include #include #include #include #include #include #include #include #include #include #include #include #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() * - __klp_sched_try_switch() */ 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 *name; unsigned long addr; unsigned long count; unsigned long pos; }; static int klp_match_callback(void *data, unsigned long addr) { struct klp_find_arg *args = data; 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_callback(void *data, const char *name, unsigned long addr) { struct klp_find_arg *args = data; if (strcmp(args->name, name)) return 0; return klp_match_callback(data, addr); } static int klp_find_object_symbol(const char *objname, const char *name, unsigned long sympos, unsigned long *addr) { struct klp_find_arg args = { .name = name, .addr = 0, .count = 0, .pos = sympos, }; if (objname) module_kallsyms_on_each_symbol(objname, klp_find_callback, &args); else kallsyms_on_each_match_symbol(klp_match_callback, name, &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 != 512); 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[^.].%511[^,],%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\n", 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; } void __weak clear_relocate_add(Elf_Shdr *sechdrs, const char *strtab, unsigned int symindex, unsigned int relsec, struct module *me) { } /* * 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. */ static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs, const char *shstrtab, const char *strtab, unsigned int symndx, unsigned int secndx, const char *objname, bool apply) { 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; if (apply) { ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname); if (ret) return ret; return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod); } clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod); return 0; } 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) { return klp_write_section_relocs(pmod, sechdrs, shstrtab, strtab, symndx, secndx, objname, true); } /* * Sysfs Interface * * /sys/kernel/livepatch * /sys/kernel/livepatch/ * /sys/kernel/livepatch//enabled * /sys/kernel/livepatch//transition * /sys/kernel/livepatch//force * /sys/kernel/livepatch// * /sys/kernel/livepatch///patched * /sys/kernel/livepatch/// */ 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 const 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 const 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 const 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 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_write_object_relocs(struct klp_patch *patch, struct klp_object *obj, bool apply) { 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_write_section_relocs(patch->mod, info->sechdrs, info->secstrings, patch->mod->core_kallsyms.strtab, info->symndx, i, obj->name, apply); if (ret) return ret; } return 0; } static int klp_apply_object_relocs(struct klp_patch *patch, struct klp_object *obj) { return klp_write_object_relocs(patch, obj, true); } static void klp_clear_object_relocs(struct klp_patch *patch, struct klp_object *obj) { klp_write_object_relocs(patch, obj, false); } /* 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_clear_object_relocs(patch, 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\n"); 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);