diff options
Diffstat (limited to 'kernel/livepatch/core.c')
| -rw-r--r-- | kernel/livepatch/core.c | 1182 |
1 files changed, 742 insertions, 440 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 5b77a7314e01..9917756dae46 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -1,21 +1,9 @@ +// 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 - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License - * as published by the Free Software Foundation; either version 2 - * of the License, or (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, see <http://www.gnu.org/licenses/>. */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt @@ -30,9 +18,12 @@ #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" /* @@ -42,10 +33,16 @@ * * - klp_ftrace_handler() * - klp_update_patch_state() + * - __klp_sched_try_switch() */ DEFINE_MUTEX(klp_mutex); -static LIST_HEAD(klp_patches); +/* + * 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; @@ -62,7 +59,7 @@ static void klp_find_object_module(struct klp_object *obj) if (!klp_is_module(obj)) return; - mutex_lock(&module_mutex); + guard(rcu)(); /* * We do not want to block removal of patched modules and therefore * we do not take a reference here. The patches are removed by @@ -78,48 +75,64 @@ static void klp_find_object_module(struct klp_object *obj) */ if (mod && mod->klp_alive) obj->mod = mod; +} - mutex_unlock(&module_mutex); +static bool klp_initialized(void) +{ + return !!klp_root_kobj; } -static bool klp_is_patch_registered(struct klp_patch *patch) +static struct klp_func *klp_find_func(struct klp_object *obj, + struct klp_func *old_func) { - struct klp_patch *mypatch; + struct klp_func *func; - list_for_each_entry(mypatch, &klp_patches, list) - if (mypatch == patch) - return true; + klp_for_each_func(obj, func) { + /* + * Besides identical old_sympos, also consider old_sympos + * of 0 and 1 are identical. + */ + if ((strcmp(old_func->old_name, func->old_name) == 0) && + ((old_func->old_sympos == func->old_sympos) || + (old_func->old_sympos == 0 && func->old_sympos == 1) || + (old_func->old_sympos == 1 && func->old_sympos == 0))) { + return func; + } + } - return false; + return NULL; } -static bool klp_initialized(void) +static struct klp_object *klp_find_object(struct klp_patch *patch, + struct klp_object *old_obj) { - return !!klp_root_kobj; + 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) +static int klp_match_callback(void *data, 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++; @@ -134,23 +147,30 @@ static int klp_find_callback(void *data, const char *name, 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 = { - .objname = objname, .name = name, .addr = 0, .count = 0, .pos = sympos, }; - mutex_lock(&module_mutex); if (objname) - module_kallsyms_on_each_symbol(klp_find_callback, &args); + module_kallsyms_on_each_symbol(objname, klp_find_callback, &args); else - kallsyms_on_each_symbol(klp_find_callback, &args); - mutex_unlock(&module_mutex); + kallsyms_on_each_match_symbol(klp_match_callback, name, &args); /* * Ensure an address was found. If sympos is 0, ensure symbol is unique; @@ -173,18 +193,21 @@ static int klp_find_object_symbol(const char *objname, const char *name, return -EINVAL; } -static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod) +static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab, + unsigned int symndx, Elf_Shdr *relasec, + const char *sec_objname) { - int i, cnt, vmlinux, ret; - char objname[MODULE_NAME_LEN]; - char symname[KSYM_NAME_LEN]; - char *strtab = pmod->core_kallsyms.strtab; + 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 objname and symname in the sscanf() + * 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. @@ -193,254 +216,131 @@ static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod) * 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); + 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 = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info); + 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); + pr_err("symbol %s at rela sec %u idx %d is not marked as a livepatch symbol\n", + strtab + sym->st_name, symndx, i); return -EINVAL; } - /* Format: .klp.sym.objname.symname,sympos */ + /* Format: .klp.sym.sym_objname.sym_name,sympos */ cnt = sscanf(strtab + sym->st_name, - ".klp.sym.%55[^.].%127[^,],%lu", - objname, symname, &sympos); + KLP_SYM_PREFIX "%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; } - /* klp_find_object_symbol() treats a NULL objname as vmlinux */ - vmlinux = !strcmp(objname, "vmlinux"); - ret = klp_find_object_symbol(vmlinux ? NULL : objname, - symname, sympos, &addr); - if (ret) - return ret; - - sym->st_value = addr; - } - - return 0; -} - -static int klp_write_object_relocations(struct module *pmod, - struct klp_object *obj) -{ - int i, cnt, ret = 0; - const char *objname, *secname; - char sec_objname[MODULE_NAME_LEN]; - Elf_Shdr *sec; - - if (WARN_ON(!klp_is_object_loaded(obj))) - return -EINVAL; - - objname = klp_is_module(obj) ? obj->name : "vmlinux"; - - /* For each klp relocation section */ - for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) { - sec = pmod->klp_info->sechdrs + i; - secname = pmod->klp_info->secstrings + sec->sh_name; - if (!(sec->sh_flags & SHF_RELA_LIVEPATCH)) - continue; + sym_vmlinux = !strcmp(sym_objname, "vmlinux"); /* - * Format: .klp.rela.sec_objname.section_name - * See comment in klp_resolve_symbols() for an explanation - * of the selected field width value. + * 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. */ - cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname); - if (cnt != 1) { - pr_err("section %s has an incorrectly formatted name\n", - secname); - ret = -EINVAL; - break; + if (!sec_vmlinux && sym_vmlinux) { + pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section\n", + sym_name); + return -EINVAL; } - if (strcmp(objname, sec_objname)) - continue; - - ret = klp_resolve_symbols(sec, pmod); + /* 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) - break; + return ret; - ret = apply_relocate_add(pmod->klp_info->sechdrs, - pmod->core_kallsyms.strtab, - pmod->klp_info->symndx, i, pmod); - if (ret) - break; + sym->st_value = addr; } - return ret; + return 0; } -static int __klp_disable_patch(struct klp_patch *patch) +void __weak clear_relocate_add(Elf_Shdr *sechdrs, + const char *strtab, + unsigned int symindex, + unsigned int relsec, + struct module *me) { - struct klp_object *obj; - - if (WARN_ON(!patch->enabled)) - return -EINVAL; - - if (klp_transition_patch) - return -EBUSY; - - /* enforce stacking: only the last enabled patch can be disabled */ - if (!list_is_last(&patch->list, &klp_patches) && - list_next_entry(patch, list)->enabled) - 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(); - klp_try_complete_transition(); - patch->enabled = false; - - return 0; } -/** - * klp_disable_patch() - disables a registered patch - * @patch: The registered, enabled patch to be disabled +/* + * 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: * - * Unregisters the patched functions from ftrace. + * 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. * - * Return: 0 on success, otherwise error + * 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_disable_patch(struct klp_patch *patch) +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 ret; - - mutex_lock(&klp_mutex); - - if (!klp_is_patch_registered(patch)) { - ret = -EINVAL; - goto err; - } - - if (!patch->enabled) { - ret = -EINVAL; - goto err; - } - - ret = __klp_disable_patch(patch); - -err: - mutex_unlock(&klp_mutex); - return ret; -} -EXPORT_SYMBOL_GPL(klp_disable_patch); - -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; - - /* enforce stacking: only the first disabled patch can be enabled */ - if (patch->list.prev != &klp_patches && - !list_prev_entry(patch, list)->enabled) - return -EBUSY; - - /* - * A reference is taken on the patch module to prevent it from being - * unloaded. - */ - if (!try_module_get(patch->mod)) - return -ENODEV; - - pr_notice("enabling patch '%s'\n", patch->mod->name); - - klp_init_transition(patch, KLP_PATCHED); + int cnt, ret; + char sec_objname[MODULE_NAME_LEN]; + Elf_Shdr *sec = sechdrs + secndx; /* - * 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. + * Format: .klp.rela.sec_objname.section_name + * See comment in klp_resolve_symbols() for an explanation + * of the selected field width value. */ - smp_wmb(); + cnt = sscanf(shstrtab + sec->sh_name, KLP_RELOC_SEC_PREFIX "%55[^.]", + sec_objname); + if (cnt != 1) { + pr_err("section %s has an incorrectly formatted name\n", + shstrtab + sec->sh_name); + return -EINVAL; + } - klp_for_each_object(patch, obj) { - if (!klp_is_object_loaded(obj)) - continue; + if (strcmp(objname ? objname : "vmlinux", sec_objname)) + return 0; - 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; - } + if (apply) { + ret = klp_resolve_symbols(sechdrs, strtab, symndx, + sec, sec_objname); + if (ret) + return ret; - ret = klp_patch_object(obj); - if (ret) { - pr_warn("failed to patch object '%s'\n", - klp_is_module(obj) ? obj->name : "vmlinux"); - goto err; - } + return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod); } - klp_start_transition(); - klp_try_complete_transition(); - patch->enabled = true; - + clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod); return 0; -err: - pr_warn("failed to enable patch '%s'\n", patch->mod->name); - - klp_cancel_transition(); - return ret; } -/** - * klp_enable_patch() - enables a registered patch - * @patch: The registered, disabled patch to be enabled - * - * Performs the needed symbol lookups and code relocations, - * then registers the patched functions with ftrace. - * - * Return: 0 on success, otherwise error - */ -int klp_enable_patch(struct klp_patch *patch) +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 ret; - - mutex_lock(&klp_mutex); - - if (!klp_is_patch_registered(patch)) { - ret = -EINVAL; - goto err; - } - - ret = __klp_enable_patch(patch); - -err: - mutex_unlock(&klp_mutex); - return ret; + return klp_write_section_relocs(pmod, sechdrs, shstrtab, strtab, symndx, + secndx, objname, true); } -EXPORT_SYMBOL_GPL(klp_enable_patch); /* * Sysfs Interface @@ -449,11 +349,14 @@ EXPORT_SYMBOL_GPL(klp_enable_patch); * /sys/kernel/livepatch/<patch> * /sys/kernel/livepatch/<patch>/enabled * /sys/kernel/livepatch/<patch>/transition - * /sys/kernel/livepatch/<patch>/signal * /sys/kernel/livepatch/<patch>/force + * /sys/kernel/livepatch/<patch>/replace + * /sys/kernel/livepatch/<patch>/stack_order * /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) @@ -470,40 +373,32 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, mutex_lock(&klp_mutex); - if (!klp_is_patch_registered(patch)) { - /* - * Module with the patch could either disappear meanwhile or is - * not properly initialized yet. - */ - ret = -EINVAL; - goto err; - } - if (patch->enabled == enabled) { /* already in requested state */ ret = -EINVAL; - goto err; + goto out; } - if (patch == klp_transition_patch) { + /* + * 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_enable_patch(patch); - if (ret) - goto err; - } else { + else if (!enabled) ret = __klp_disable_patch(patch); - if (ret) - goto err; - } + else + ret = -EINVAL; +out: mutex_unlock(&klp_mutex); + if (ret) + return ret; return count; - -err: - mutex_unlock(&klp_mutex); - return ret; } static ssize_t enabled_show(struct kobject *kobj, @@ -512,7 +407,7 @@ static ssize_t enabled_show(struct kobject *kobj, struct klp_patch *patch; patch = container_of(kobj, struct klp_patch, kobj); - return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled); + return sysfs_emit(buf, "%d\n", patch->enabled); } static ssize_t transition_show(struct kobject *kobj, @@ -521,12 +416,11 @@ static ssize_t transition_show(struct kobject *kobj, struct klp_patch *patch; patch = container_of(kobj, struct klp_patch, kobj); - return snprintf(buf, PAGE_SIZE-1, "%d\n", - patch == klp_transition_patch); + return sysfs_emit(buf, "%d\n", patch == klp_transition_patch); } -static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr, - const char *buf, size_t count) +static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr, + const char *buf, size_t count) { struct klp_patch *patch; int ret; @@ -547,53 +441,194 @@ static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr, return -EINVAL; } - klp_send_signals(); + klp_force_transition(); mutex_unlock(&klp_mutex); return count; } -static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr, - const char *buf, size_t count) +static ssize_t replace_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) { struct klp_patch *patch; - int ret; - bool val; - ret = kstrtobool(buf, &val); - if (ret) - return ret; + patch = container_of(kobj, struct klp_patch, kobj); + return sysfs_emit(buf, "%d\n", patch->replace); +} - if (!val) - return count; +static ssize_t stack_order_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + struct klp_patch *patch, *this_patch; + int stack_order = 0; + + this_patch = container_of(kobj, struct klp_patch, kobj); mutex_lock(&klp_mutex); - patch = container_of(kobj, struct klp_patch, kobj); - if (patch != klp_transition_patch) { - mutex_unlock(&klp_mutex); - return -EINVAL; + klp_for_each_patch(patch) { + stack_order++; + if (patch == this_patch) + break; } - klp_force_transition(); - mutex_unlock(&klp_mutex); - return count; + return sysfs_emit(buf, "%d\n", stack_order); } static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled); static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition); -static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal); static struct kobj_attribute force_kobj_attr = __ATTR_WO(force); +static struct kobj_attribute replace_kobj_attr = __ATTR_RO(replace); +static struct kobj_attribute stack_order_kobj_attr = __ATTR_RO(stack_order); static struct attribute *klp_patch_attrs[] = { &enabled_kobj_attr.attr, &transition_kobj_attr.attr, - &signal_kobj_attr.attr, &force_kobj_attr.attr, + &replace_kobj_attr.attr, + &stack_order_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. + * + * They are added only when the atomic replace mode is used and only for + * functions which are currently livepatched but are no longer included + * in the new livepatch. + */ +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) { @@ -603,41 +638,54 @@ static void klp_kobj_release_patch(struct kobject *kobj) complete(&patch->finish); } -static struct kobj_type klp_ktype_patch = { +static const struct kobj_type klp_ktype_patch = { .release = klp_kobj_release_patch, .sysfs_ops = &kobj_sysfs_ops, - .default_attrs = klp_patch_attrs, + .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 = { +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 struct kobj_type klp_ktype_func = { +static const struct kobj_type klp_ktype_func = { .release = klp_kobj_release_func, .sysfs_ops = &kobj_sysfs_ops, }; -/* - * Free all functions' kobjects in the array up to some limit. When limit is - * NULL, all kobjects are freed. - */ -static void klp_free_funcs_limited(struct klp_object *obj, - struct klp_func *limit) +static void __klp_free_funcs(struct klp_object *obj, bool nops_only) { - struct klp_func *func; + struct klp_func *func, *tmp_func; - for (func = obj->funcs; func->old_name && func != limit; 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 */ @@ -647,35 +695,118 @@ static void klp_free_object_loaded(struct klp_object *obj) obj->mod = NULL; - klp_for_each_func(obj, func) - func->old_addr = 0; + klp_for_each_func(obj, func) { + func->old_func = NULL; + + if (func->nop) + func->new_func = NULL; + } } -/* - * Free all objects' kobjects in the array up to some limit. When limit is - * NULL, all kobjects are freed. - */ -static void klp_free_objects_limited(struct klp_patch *patch, - struct klp_object *limit) +static void __klp_free_objects(struct klp_patch *patch, bool nops_only) { - struct klp_object *obj; + struct klp_object *obj, *tmp_obj; + + klp_for_each_object_safe(patch, obj, tmp_obj) { + __klp_free_funcs(obj, nops_only); - for (obj = patch->objs; obj->funcs && obj != limit; obj++) { - klp_free_funcs_limited(obj, NULL); + if (nops_only && !obj->dynamic) + continue; + + list_del(&obj->node); kobject_put(&obj->kobj); } } -static void klp_free_patch(struct klp_patch *patch) +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) { - klp_free_objects_limited(patch, NULL); 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 || !func->new_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) @@ -690,15 +821,45 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func) * 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_init_and_add(&func->kobj, &klp_ktype_func, - &obj->kobj, "%s,%lu", func->old_name, - func->old_sympos ? func->old_sympos : 1); + return kobject_add(&func->kobj, &obj->kobj, "%s,%lu", + func->old_name, + func->old_sympos ? func->old_sympos : 1); } -/* Arches may override this to finish any remaining arch-specific tasks */ -void __weak arch_klp_init_object_loaded(struct klp_patch *patch, - struct klp_object *obj) +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 */ @@ -708,24 +869,26 @@ static int klp_init_object_loaded(struct klp_patch *patch, struct klp_func *func; int ret; - module_disable_ro(patch->mod); - ret = klp_write_object_relocations(patch->mod, obj); - if (ret) { - module_enable_ro(patch->mod, true); - return 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; } - arch_klp_init_object_loaded(patch, obj); - module_enable_ro(patch->mod, true); - klp_for_each_func(obj, func) { ret = klp_find_object_symbol(obj->name, func->old_name, func->old_sympos, - &func->old_addr); + (unsigned long *)&func->old_func); if (ret) return ret; - ret = kallsyms_lookup_size_offset(func->old_addr, + 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", @@ -733,6 +896,9 @@ static int klp_init_object_loaded(struct klp_patch *patch, 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) { @@ -751,9 +917,6 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) int ret; const char *name; - if (!obj->funcs) - return -EINVAL; - if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN) return -EINVAL; @@ -763,129 +926,199 @@ static int klp_init_object(struct klp_patch *patch, struct klp_object *obj) klp_find_object_module(obj); name = klp_is_module(obj) ? obj->name : "vmlinux"; - ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object, - &patch->kobj, "%s", name); + 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) - goto free; + return ret; } - if (klp_is_object_loaded(obj)) { + if (klp_is_object_loaded(obj)) ret = klp_init_object_loaded(patch, obj); - if (ret) - goto free; - } - - return 0; -free: - klp_free_funcs_limited(obj, func); - kobject_put(&obj->kobj); return ret; } -static int klp_init_patch(struct klp_patch *patch) +static void klp_init_func_early(struct klp_object *obj, + struct klp_func *func) { - struct klp_object *obj; - int ret; + kobject_init(&func->kobj, &klp_ktype_func); + list_add_tail(&func->node, &obj->func_list); +} - if (!patch->objs) - return -EINVAL; +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); +} - mutex_lock(&klp_mutex); +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); - ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch, - klp_root_kobj, "%s", patch->mod->name); - if (ret) { - mutex_unlock(&klp_mutex); + 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) - goto free; + return ret; } list_add_tail(&patch->list, &klp_patches); - mutex_unlock(&klp_mutex); - return 0; +} -free: - klp_free_objects_limited(patch, obj); +static int __klp_disable_patch(struct klp_patch *patch) +{ + struct klp_object *obj; - mutex_unlock(&klp_mutex); + if (WARN_ON(!patch->enabled)) + return -EINVAL; - kobject_put(&patch->kobj); - wait_for_completion(&patch->finish); + if (klp_transition_patch) + return -EBUSY; - return ret; + klp_init_transition(patch, KLP_TRANSITION_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; } -/** - * klp_unregister_patch() - unregisters a patch - * @patch: Disabled patch to be unregistered - * - * Frees the data structures and removes the sysfs interface. - * - * Return: 0 on success, otherwise error - */ -int klp_unregister_patch(struct klp_patch *patch) +static int __klp_enable_patch(struct klp_patch *patch) { + struct klp_object *obj; int ret; - mutex_lock(&klp_mutex); + if (klp_transition_patch) + return -EBUSY; - if (!klp_is_patch_registered(patch)) { - ret = -EINVAL; - goto err; - } + if (WARN_ON(patch->enabled)) + return -EINVAL; - if (patch->enabled) { - ret = -EBUSY; - goto err; - } + pr_notice("enabling patch '%s'\n", patch->mod->name); - klp_free_patch(patch); + klp_init_transition(patch, KLP_TRANSITION_PATCHED); - mutex_unlock(&klp_mutex); + /* + * 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(); - kobject_put(&patch->kobj); - wait_for_completion(&patch->finish); + 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: - mutex_unlock(&klp_mutex); + pr_warn("failed to enable patch '%s'\n", patch->mod->name); + + klp_cancel_transition(); return ret; } -EXPORT_SYMBOL_GPL(klp_unregister_patch); /** - * klp_register_patch() - registers a patch - * @patch: Patch to be registered + * klp_enable_patch() - enable the livepatch + * @patch: patch to be enabled * - * Initializes the data structure associated with the patch and - * creates the sysfs interface. + * 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. * - * There is no need to take the reference on the patch module here. It is done - * later when the patch is enabled. + * This function is supposed to be called from the livepatch module_init() + * callback. * * Return: 0 on success, otherwise error */ -int klp_register_patch(struct klp_patch *patch) +int klp_enable_patch(struct klp_patch *patch) { - if (!patch || !patch->mod) + 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); @@ -896,13 +1129,98 @@ int klp_register_patch(struct klp_patch *patch) return -ENODEV; if (!klp_have_reliable_stack()) { - pr_err("This architecture doesn't have support for the livepatch consistency model.\n"); - return -ENOSYS; + 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; } - return klp_init_patch(patch); + 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); } -EXPORT_SYMBOL_GPL(klp_register_patch); /* * Remove parts of patches that touch a given kernel module. The list of @@ -915,7 +1233,7 @@ static void klp_cleanup_module_patches_limited(struct module *mod, struct klp_patch *patch; struct klp_object *obj; - list_for_each_entry(patch, &klp_patches, list) { + klp_for_each_patch(patch) { if (patch == limit) break; @@ -923,22 +1241,15 @@ static void klp_cleanup_module_patches_limited(struct module *mod, if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) continue; - /* - * Only unpatch the module if the patch is enabled or - * is in transition. - */ - if (patch->enabled || patch == klp_transition_patch) { - - 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); + if (patch != klp_transition_patch) + klp_pre_unpatch_callback(obj); - klp_post_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; } @@ -954,6 +1265,11 @@ int klp_module_coming(struct module *mod) 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() @@ -962,7 +1278,7 @@ int klp_module_coming(struct module *mod) */ mod->klp_alive = true; - list_for_each_entry(patch, &klp_patches, list) { + klp_for_each_patch(patch) { klp_for_each_object(patch, obj) { if (!klp_is_module(obj) || strcmp(obj->name, mod->name)) continue; @@ -976,13 +1292,6 @@ int klp_module_coming(struct module *mod) goto err; } - /* - * Only patch the module if the patch is enabled or is - * in transition. - */ - if (!patch->enabled && patch != klp_transition_patch) - break; - pr_notice("applying patch '%s' to loading module '%s'\n", patch->mod->name, obj->mod->name); @@ -1021,6 +1330,7 @@ err: 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); @@ -1048,14 +1358,6 @@ void klp_module_going(struct module *mod) static int __init klp_init(void) { - int ret; - - ret = klp_check_compiler_support(); - if (ret) { - pr_info("Your compiler is too old; turning off.\n"); - return -EINVAL; - } - klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj); if (!klp_root_kobj) return -ENOMEM; |