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1/*
2 * core.c - Kernel Live Patching Core
3 *
4 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
5 * Copyright (C) 2014 SUSE
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2
10 * of the License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, see <http://www.gnu.org/licenses/>.
19 */
20
21#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
22
23#include <linux/module.h>
24#include <linux/kernel.h>
25#include <linux/mutex.h>
26#include <linux/slab.h>
27#include <linux/list.h>
28#include <linux/kallsyms.h>
29#include <linux/livepatch.h>
30#include <linux/elf.h>
31#include <linux/moduleloader.h>
32#include <linux/completion.h>
33#include <asm/cacheflush.h>
34#include "core.h"
35#include "patch.h"
36#include "transition.h"
37
38/*
39 * klp_mutex is a coarse lock which serializes access to klp data. All
40 * accesses to klp-related variables and structures must have mutex protection,
41 * except within the following functions which carefully avoid the need for it:
42 *
43 * - klp_ftrace_handler()
44 * - klp_update_patch_state()
45 */
46DEFINE_MUTEX(klp_mutex);
47
48static LIST_HEAD(klp_patches);
49
50static struct kobject *klp_root_kobj;
51
52static bool klp_is_module(struct klp_object *obj)
53{
54 return obj->name;
55}
56
57/* sets obj->mod if object is not vmlinux and module is found */
58static void klp_find_object_module(struct klp_object *obj)
59{
60 struct module *mod;
61
62 if (!klp_is_module(obj))
63 return;
64
65 mutex_lock(&module_mutex);
66 /*
67 * We do not want to block removal of patched modules and therefore
68 * we do not take a reference here. The patches are removed by
69 * klp_module_going() instead.
70 */
71 mod = find_module(obj->name);
72 /*
73 * Do not mess work of klp_module_coming() and klp_module_going().
74 * Note that the patch might still be needed before klp_module_going()
75 * is called. Module functions can be called even in the GOING state
76 * until mod->exit() finishes. This is especially important for
77 * patches that modify semantic of the functions.
78 */
79 if (mod && mod->klp_alive)
80 obj->mod = mod;
81
82 mutex_unlock(&module_mutex);
83}
84
85static bool klp_is_patch_registered(struct klp_patch *patch)
86{
87 struct klp_patch *mypatch;
88
89 list_for_each_entry(mypatch, &klp_patches, list)
90 if (mypatch == patch)
91 return true;
92
93 return false;
94}
95
96static bool klp_initialized(void)
97{
98 return !!klp_root_kobj;
99}
100
101struct klp_find_arg {
102 const char *objname;
103 const char *name;
104 unsigned long addr;
105 unsigned long count;
106 unsigned long pos;
107};
108
109static int klp_find_callback(void *data, const char *name,
110 struct module *mod, unsigned long addr)
111{
112 struct klp_find_arg *args = data;
113
114 if ((mod && !args->objname) || (!mod && args->objname))
115 return 0;
116
117 if (strcmp(args->name, name))
118 return 0;
119
120 if (args->objname && strcmp(args->objname, mod->name))
121 return 0;
122
123 args->addr = addr;
124 args->count++;
125
126 /*
127 * Finish the search when the symbol is found for the desired position
128 * or the position is not defined for a non-unique symbol.
129 */
130 if ((args->pos && (args->count == args->pos)) ||
131 (!args->pos && (args->count > 1)))
132 return 1;
133
134 return 0;
135}
136
137static int klp_find_object_symbol(const char *objname, const char *name,
138 unsigned long sympos, unsigned long *addr)
139{
140 struct klp_find_arg args = {
141 .objname = objname,
142 .name = name,
143 .addr = 0,
144 .count = 0,
145 .pos = sympos,
146 };
147
148 mutex_lock(&module_mutex);
149 if (objname)
150 module_kallsyms_on_each_symbol(klp_find_callback, &args);
151 else
152 kallsyms_on_each_symbol(klp_find_callback, &args);
153 mutex_unlock(&module_mutex);
154
155 /*
156 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
157 * otherwise ensure the symbol position count matches sympos.
158 */
159 if (args.addr == 0)
160 pr_err("symbol '%s' not found in symbol table\n", name);
161 else if (args.count > 1 && sympos == 0) {
162 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
163 name, objname);
164 } else if (sympos != args.count && sympos > 0) {
165 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
166 sympos, name, objname ? objname : "vmlinux");
167 } else {
168 *addr = args.addr;
169 return 0;
170 }
171
172 *addr = 0;
173 return -EINVAL;
174}
175
176static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
177{
178 int i, cnt, vmlinux, ret;
179 char objname[MODULE_NAME_LEN];
180 char symname[KSYM_NAME_LEN];
181 char *strtab = pmod->core_kallsyms.strtab;
182 Elf_Rela *relas;
183 Elf_Sym *sym;
184 unsigned long sympos, addr;
185
186 /*
187 * Since the field widths for objname and symname in the sscanf()
188 * call are hard-coded and correspond to MODULE_NAME_LEN and
189 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
190 * and KSYM_NAME_LEN have the values we expect them to have.
191 *
192 * Because the value of MODULE_NAME_LEN can differ among architectures,
193 * we use the smallest/strictest upper bound possible (56, based on
194 * the current definition of MODULE_NAME_LEN) to prevent overflows.
195 */
196 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
197
198 relas = (Elf_Rela *) relasec->sh_addr;
199 /* For each rela in this klp relocation section */
200 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
201 sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
202 if (sym->st_shndx != SHN_LIVEPATCH) {
203 pr_err("symbol %s is not marked as a livepatch symbol\n",
204 strtab + sym->st_name);
205 return -EINVAL;
206 }
207
208 /* Format: .klp.sym.objname.symname,sympos */
209 cnt = sscanf(strtab + sym->st_name,
210 ".klp.sym.%55[^.].%127[^,],%lu",
211 objname, symname, &sympos);
212 if (cnt != 3) {
213 pr_err("symbol %s has an incorrectly formatted name\n",
214 strtab + sym->st_name);
215 return -EINVAL;
216 }
217
218 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
219 vmlinux = !strcmp(objname, "vmlinux");
220 ret = klp_find_object_symbol(vmlinux ? NULL : objname,
221 symname, sympos, &addr);
222 if (ret)
223 return ret;
224
225 sym->st_value = addr;
226 }
227
228 return 0;
229}
230
231static int klp_write_object_relocations(struct module *pmod,
232 struct klp_object *obj)
233{
234 int i, cnt, ret = 0;
235 const char *objname, *secname;
236 char sec_objname[MODULE_NAME_LEN];
237 Elf_Shdr *sec;
238
239 if (WARN_ON(!klp_is_object_loaded(obj)))
240 return -EINVAL;
241
242 objname = klp_is_module(obj) ? obj->name : "vmlinux";
243
244 /* For each klp relocation section */
245 for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
246 sec = pmod->klp_info->sechdrs + i;
247 secname = pmod->klp_info->secstrings + sec->sh_name;
248 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
249 continue;
250
251 /*
252 * Format: .klp.rela.sec_objname.section_name
253 * See comment in klp_resolve_symbols() for an explanation
254 * of the selected field width value.
255 */
256 cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
257 if (cnt != 1) {
258 pr_err("section %s has an incorrectly formatted name\n",
259 secname);
260 ret = -EINVAL;
261 break;
262 }
263
264 if (strcmp(objname, sec_objname))
265 continue;
266
267 ret = klp_resolve_symbols(sec, pmod);
268 if (ret)
269 break;
270
271 ret = apply_relocate_add(pmod->klp_info->sechdrs,
272 pmod->core_kallsyms.strtab,
273 pmod->klp_info->symndx, i, pmod);
274 if (ret)
275 break;
276 }
277
278 return ret;
279}
280
281static int __klp_disable_patch(struct klp_patch *patch)
282{
283 struct klp_object *obj;
284
285 if (WARN_ON(!patch->enabled))
286 return -EINVAL;
287
288 if (klp_transition_patch)
289 return -EBUSY;
290
291 /* enforce stacking: only the last enabled patch can be disabled */
292 if (!list_is_last(&patch->list, &klp_patches) &&
293 list_next_entry(patch, list)->enabled)
294 return -EBUSY;
295
296 klp_init_transition(patch, KLP_UNPATCHED);
297
298 klp_for_each_object(patch, obj)
299 if (obj->patched)
300 klp_pre_unpatch_callback(obj);
301
302 /*
303 * Enforce the order of the func->transition writes in
304 * klp_init_transition() and the TIF_PATCH_PENDING writes in
305 * klp_start_transition(). In the rare case where klp_ftrace_handler()
306 * is called shortly after klp_update_patch_state() switches the task,
307 * this ensures the handler sees that func->transition is set.
308 */
309 smp_wmb();
310
311 klp_start_transition();
312 klp_try_complete_transition();
313 patch->enabled = false;
314
315 return 0;
316}
317
318/**
319 * klp_disable_patch() - disables a registered patch
320 * @patch: The registered, enabled patch to be disabled
321 *
322 * Unregisters the patched functions from ftrace.
323 *
324 * Return: 0 on success, otherwise error
325 */
326int klp_disable_patch(struct klp_patch *patch)
327{
328 int ret;
329
330 mutex_lock(&klp_mutex);
331
332 if (!klp_is_patch_registered(patch)) {
333 ret = -EINVAL;
334 goto err;
335 }
336
337 if (!patch->enabled) {
338 ret = -EINVAL;
339 goto err;
340 }
341
342 ret = __klp_disable_patch(patch);
343
344err:
345 mutex_unlock(&klp_mutex);
346 return ret;
347}
348EXPORT_SYMBOL_GPL(klp_disable_patch);
349
350static int __klp_enable_patch(struct klp_patch *patch)
351{
352 struct klp_object *obj;
353 int ret;
354
355 if (klp_transition_patch)
356 return -EBUSY;
357
358 if (WARN_ON(patch->enabled))
359 return -EINVAL;
360
361 /* enforce stacking: only the first disabled patch can be enabled */
362 if (patch->list.prev != &klp_patches &&
363 !list_prev_entry(patch, list)->enabled)
364 return -EBUSY;
365
366 /*
367 * A reference is taken on the patch module to prevent it from being
368 * unloaded.
369 */
370 if (!try_module_get(patch->mod))
371 return -ENODEV;
372
373 pr_notice("enabling patch '%s'\n", patch->mod->name);
374
375 klp_init_transition(patch, KLP_PATCHED);
376
377 /*
378 * Enforce the order of the func->transition writes in
379 * klp_init_transition() and the ops->func_stack writes in
380 * klp_patch_object(), so that klp_ftrace_handler() will see the
381 * func->transition updates before the handler is registered and the
382 * new funcs become visible to the handler.
383 */
384 smp_wmb();
385
386 klp_for_each_object(patch, obj) {
387 if (!klp_is_object_loaded(obj))
388 continue;
389
390 ret = klp_pre_patch_callback(obj);
391 if (ret) {
392 pr_warn("pre-patch callback failed for object '%s'\n",
393 klp_is_module(obj) ? obj->name : "vmlinux");
394 goto err;
395 }
396
397 ret = klp_patch_object(obj);
398 if (ret) {
399 pr_warn("failed to patch object '%s'\n",
400 klp_is_module(obj) ? obj->name : "vmlinux");
401 goto err;
402 }
403 }
404
405 klp_start_transition();
406 klp_try_complete_transition();
407 patch->enabled = true;
408
409 return 0;
410err:
411 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
412
413 klp_cancel_transition();
414 return ret;
415}
416
417/**
418 * klp_enable_patch() - enables a registered patch
419 * @patch: The registered, disabled patch to be enabled
420 *
421 * Performs the needed symbol lookups and code relocations,
422 * then registers the patched functions with ftrace.
423 *
424 * Return: 0 on success, otherwise error
425 */
426int klp_enable_patch(struct klp_patch *patch)
427{
428 int ret;
429
430 mutex_lock(&klp_mutex);
431
432 if (!klp_is_patch_registered(patch)) {
433 ret = -EINVAL;
434 goto err;
435 }
436
437 ret = __klp_enable_patch(patch);
438
439err:
440 mutex_unlock(&klp_mutex);
441 return ret;
442}
443EXPORT_SYMBOL_GPL(klp_enable_patch);
444
445/*
446 * Sysfs Interface
447 *
448 * /sys/kernel/livepatch
449 * /sys/kernel/livepatch/<patch>
450 * /sys/kernel/livepatch/<patch>/enabled
451 * /sys/kernel/livepatch/<patch>/transition
452 * /sys/kernel/livepatch/<patch>/signal
453 * /sys/kernel/livepatch/<patch>/force
454 * /sys/kernel/livepatch/<patch>/<object>
455 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
456 */
457
458static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
459 const char *buf, size_t count)
460{
461 struct klp_patch *patch;
462 int ret;
463 bool enabled;
464
465 ret = kstrtobool(buf, &enabled);
466 if (ret)
467 return ret;
468
469 patch = container_of(kobj, struct klp_patch, kobj);
470
471 mutex_lock(&klp_mutex);
472
473 if (!klp_is_patch_registered(patch)) {
474 /*
475 * Module with the patch could either disappear meanwhile or is
476 * not properly initialized yet.
477 */
478 ret = -EINVAL;
479 goto err;
480 }
481
482 if (patch->enabled == enabled) {
483 /* already in requested state */
484 ret = -EINVAL;
485 goto err;
486 }
487
488 if (patch == klp_transition_patch) {
489 klp_reverse_transition();
490 } else if (enabled) {
491 ret = __klp_enable_patch(patch);
492 if (ret)
493 goto err;
494 } else {
495 ret = __klp_disable_patch(patch);
496 if (ret)
497 goto err;
498 }
499
500 mutex_unlock(&klp_mutex);
501
502 return count;
503
504err:
505 mutex_unlock(&klp_mutex);
506 return ret;
507}
508
509static ssize_t enabled_show(struct kobject *kobj,
510 struct kobj_attribute *attr, char *buf)
511{
512 struct klp_patch *patch;
513
514 patch = container_of(kobj, struct klp_patch, kobj);
515 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
516}
517
518static ssize_t transition_show(struct kobject *kobj,
519 struct kobj_attribute *attr, char *buf)
520{
521 struct klp_patch *patch;
522
523 patch = container_of(kobj, struct klp_patch, kobj);
524 return snprintf(buf, PAGE_SIZE-1, "%d\n",
525 patch == klp_transition_patch);
526}
527
528static ssize_t signal_store(struct kobject *kobj, struct kobj_attribute *attr,
529 const char *buf, size_t count)
530{
531 struct klp_patch *patch;
532 int ret;
533 bool val;
534
535 ret = kstrtobool(buf, &val);
536 if (ret)
537 return ret;
538
539 if (!val)
540 return count;
541
542 mutex_lock(&klp_mutex);
543
544 patch = container_of(kobj, struct klp_patch, kobj);
545 if (patch != klp_transition_patch) {
546 mutex_unlock(&klp_mutex);
547 return -EINVAL;
548 }
549
550 klp_send_signals();
551
552 mutex_unlock(&klp_mutex);
553
554 return count;
555}
556
557static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
558 const char *buf, size_t count)
559{
560 struct klp_patch *patch;
561 int ret;
562 bool val;
563
564 ret = kstrtobool(buf, &val);
565 if (ret)
566 return ret;
567
568 if (!val)
569 return count;
570
571 mutex_lock(&klp_mutex);
572
573 patch = container_of(kobj, struct klp_patch, kobj);
574 if (patch != klp_transition_patch) {
575 mutex_unlock(&klp_mutex);
576 return -EINVAL;
577 }
578
579 klp_force_transition();
580
581 mutex_unlock(&klp_mutex);
582
583 return count;
584}
585
586static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
587static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
588static struct kobj_attribute signal_kobj_attr = __ATTR_WO(signal);
589static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
590static struct attribute *klp_patch_attrs[] = {
591 &enabled_kobj_attr.attr,
592 &transition_kobj_attr.attr,
593 &signal_kobj_attr.attr,
594 &force_kobj_attr.attr,
595 NULL
596};
597
598static void klp_kobj_release_patch(struct kobject *kobj)
599{
600 struct klp_patch *patch;
601
602 patch = container_of(kobj, struct klp_patch, kobj);
603 complete(&patch->finish);
604}
605
606static struct kobj_type klp_ktype_patch = {
607 .release = klp_kobj_release_patch,
608 .sysfs_ops = &kobj_sysfs_ops,
609 .default_attrs = klp_patch_attrs,
610};
611
612static void klp_kobj_release_object(struct kobject *kobj)
613{
614}
615
616static struct kobj_type klp_ktype_object = {
617 .release = klp_kobj_release_object,
618 .sysfs_ops = &kobj_sysfs_ops,
619};
620
621static void klp_kobj_release_func(struct kobject *kobj)
622{
623}
624
625static struct kobj_type klp_ktype_func = {
626 .release = klp_kobj_release_func,
627 .sysfs_ops = &kobj_sysfs_ops,
628};
629
630/*
631 * Free all functions' kobjects in the array up to some limit. When limit is
632 * NULL, all kobjects are freed.
633 */
634static void klp_free_funcs_limited(struct klp_object *obj,
635 struct klp_func *limit)
636{
637 struct klp_func *func;
638
639 for (func = obj->funcs; func->old_name && func != limit; func++)
640 kobject_put(&func->kobj);
641}
642
643/* Clean up when a patched object is unloaded */
644static void klp_free_object_loaded(struct klp_object *obj)
645{
646 struct klp_func *func;
647
648 obj->mod = NULL;
649
650 klp_for_each_func(obj, func)
651 func->old_addr = 0;
652}
653
654/*
655 * Free all objects' kobjects in the array up to some limit. When limit is
656 * NULL, all kobjects are freed.
657 */
658static void klp_free_objects_limited(struct klp_patch *patch,
659 struct klp_object *limit)
660{
661 struct klp_object *obj;
662
663 for (obj = patch->objs; obj->funcs && obj != limit; obj++) {
664 klp_free_funcs_limited(obj, NULL);
665 kobject_put(&obj->kobj);
666 }
667}
668
669static void klp_free_patch(struct klp_patch *patch)
670{
671 klp_free_objects_limited(patch, NULL);
672 if (!list_empty(&patch->list))
673 list_del(&patch->list);
674}
675
676static int klp_init_func(struct klp_object *obj, struct klp_func *func)
677{
678 if (!func->old_name || !func->new_func)
679 return -EINVAL;
680
681 INIT_LIST_HEAD(&func->stack_node);
682 func->patched = false;
683 func->transition = false;
684
685 /* The format for the sysfs directory is <function,sympos> where sympos
686 * is the nth occurrence of this symbol in kallsyms for the patched
687 * object. If the user selects 0 for old_sympos, then 1 will be used
688 * since a unique symbol will be the first occurrence.
689 */
690 return kobject_init_and_add(&func->kobj, &klp_ktype_func,
691 &obj->kobj, "%s,%lu", func->old_name,
692 func->old_sympos ? func->old_sympos : 1);
693}
694
695/* Arches may override this to finish any remaining arch-specific tasks */
696void __weak arch_klp_init_object_loaded(struct klp_patch *patch,
697 struct klp_object *obj)
698{
699}
700
701/* parts of the initialization that is done only when the object is loaded */
702static int klp_init_object_loaded(struct klp_patch *patch,
703 struct klp_object *obj)
704{
705 struct klp_func *func;
706 int ret;
707
708 module_disable_ro(patch->mod);
709 ret = klp_write_object_relocations(patch->mod, obj);
710 if (ret) {
711 module_enable_ro(patch->mod, true);
712 return ret;
713 }
714
715 arch_klp_init_object_loaded(patch, obj);
716 module_enable_ro(patch->mod, true);
717
718 klp_for_each_func(obj, func) {
719 ret = klp_find_object_symbol(obj->name, func->old_name,
720 func->old_sympos,
721 &func->old_addr);
722 if (ret)
723 return ret;
724
725 ret = kallsyms_lookup_size_offset(func->old_addr,
726 &func->old_size, NULL);
727 if (!ret) {
728 pr_err("kallsyms size lookup failed for '%s'\n",
729 func->old_name);
730 return -ENOENT;
731 }
732
733 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
734 &func->new_size, NULL);
735 if (!ret) {
736 pr_err("kallsyms size lookup failed for '%s' replacement\n",
737 func->old_name);
738 return -ENOENT;
739 }
740 }
741
742 return 0;
743}
744
745static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
746{
747 struct klp_func *func;
748 int ret;
749 const char *name;
750
751 if (!obj->funcs)
752 return -EINVAL;
753
754 obj->patched = false;
755 obj->mod = NULL;
756
757 klp_find_object_module(obj);
758
759 name = klp_is_module(obj) ? obj->name : "vmlinux";
760 ret = kobject_init_and_add(&obj->kobj, &klp_ktype_object,
761 &patch->kobj, "%s", name);
762 if (ret)
763 return ret;
764
765 klp_for_each_func(obj, func) {
766 ret = klp_init_func(obj, func);
767 if (ret)
768 goto free;
769 }
770
771 if (klp_is_object_loaded(obj)) {
772 ret = klp_init_object_loaded(patch, obj);
773 if (ret)
774 goto free;
775 }
776
777 return 0;
778
779free:
780 klp_free_funcs_limited(obj, func);
781 kobject_put(&obj->kobj);
782 return ret;
783}
784
785static int klp_init_patch(struct klp_patch *patch)
786{
787 struct klp_object *obj;
788 int ret;
789
790 if (!patch->objs)
791 return -EINVAL;
792
793 mutex_lock(&klp_mutex);
794
795 patch->enabled = false;
796 init_completion(&patch->finish);
797
798 ret = kobject_init_and_add(&patch->kobj, &klp_ktype_patch,
799 klp_root_kobj, "%s", patch->mod->name);
800 if (ret) {
801 mutex_unlock(&klp_mutex);
802 return ret;
803 }
804
805 klp_for_each_object(patch, obj) {
806 ret = klp_init_object(patch, obj);
807 if (ret)
808 goto free;
809 }
810
811 list_add_tail(&patch->list, &klp_patches);
812
813 mutex_unlock(&klp_mutex);
814
815 return 0;
816
817free:
818 klp_free_objects_limited(patch, obj);
819
820 mutex_unlock(&klp_mutex);
821
822 kobject_put(&patch->kobj);
823 wait_for_completion(&patch->finish);
824
825 return ret;
826}
827
828/**
829 * klp_unregister_patch() - unregisters a patch
830 * @patch: Disabled patch to be unregistered
831 *
832 * Frees the data structures and removes the sysfs interface.
833 *
834 * Return: 0 on success, otherwise error
835 */
836int klp_unregister_patch(struct klp_patch *patch)
837{
838 int ret;
839
840 mutex_lock(&klp_mutex);
841
842 if (!klp_is_patch_registered(patch)) {
843 ret = -EINVAL;
844 goto err;
845 }
846
847 if (patch->enabled) {
848 ret = -EBUSY;
849 goto err;
850 }
851
852 klp_free_patch(patch);
853
854 mutex_unlock(&klp_mutex);
855
856 kobject_put(&patch->kobj);
857 wait_for_completion(&patch->finish);
858
859 return 0;
860err:
861 mutex_unlock(&klp_mutex);
862 return ret;
863}
864EXPORT_SYMBOL_GPL(klp_unregister_patch);
865
866/**
867 * klp_register_patch() - registers a patch
868 * @patch: Patch to be registered
869 *
870 * Initializes the data structure associated with the patch and
871 * creates the sysfs interface.
872 *
873 * There is no need to take the reference on the patch module here. It is done
874 * later when the patch is enabled.
875 *
876 * Return: 0 on success, otherwise error
877 */
878int klp_register_patch(struct klp_patch *patch)
879{
880 if (!patch || !patch->mod)
881 return -EINVAL;
882
883 if (!is_livepatch_module(patch->mod)) {
884 pr_err("module %s is not marked as a livepatch module\n",
885 patch->mod->name);
886 return -EINVAL;
887 }
888
889 if (!klp_initialized())
890 return -ENODEV;
891
892 if (!klp_have_reliable_stack()) {
893 pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
894 return -ENOSYS;
895 }
896
897 return klp_init_patch(patch);
898}
899EXPORT_SYMBOL_GPL(klp_register_patch);
900
901/*
902 * Remove parts of patches that touch a given kernel module. The list of
903 * patches processed might be limited. When limit is NULL, all patches
904 * will be handled.
905 */
906static void klp_cleanup_module_patches_limited(struct module *mod,
907 struct klp_patch *limit)
908{
909 struct klp_patch *patch;
910 struct klp_object *obj;
911
912 list_for_each_entry(patch, &klp_patches, list) {
913 if (patch == limit)
914 break;
915
916 klp_for_each_object(patch, obj) {
917 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
918 continue;
919
920 /*
921 * Only unpatch the module if the patch is enabled or
922 * is in transition.
923 */
924 if (patch->enabled || patch == klp_transition_patch) {
925
926 if (patch != klp_transition_patch)
927 klp_pre_unpatch_callback(obj);
928
929 pr_notice("reverting patch '%s' on unloading module '%s'\n",
930 patch->mod->name, obj->mod->name);
931 klp_unpatch_object(obj);
932
933 klp_post_unpatch_callback(obj);
934 }
935
936 klp_free_object_loaded(obj);
937 break;
938 }
939 }
940}
941
942int klp_module_coming(struct module *mod)
943{
944 int ret;
945 struct klp_patch *patch;
946 struct klp_object *obj;
947
948 if (WARN_ON(mod->state != MODULE_STATE_COMING))
949 return -EINVAL;
950
951 mutex_lock(&klp_mutex);
952 /*
953 * Each module has to know that klp_module_coming()
954 * has been called. We never know what module will
955 * get patched by a new patch.
956 */
957 mod->klp_alive = true;
958
959 list_for_each_entry(patch, &klp_patches, list) {
960 klp_for_each_object(patch, obj) {
961 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
962 continue;
963
964 obj->mod = mod;
965
966 ret = klp_init_object_loaded(patch, obj);
967 if (ret) {
968 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
969 patch->mod->name, obj->mod->name, ret);
970 goto err;
971 }
972
973 /*
974 * Only patch the module if the patch is enabled or is
975 * in transition.
976 */
977 if (!patch->enabled && patch != klp_transition_patch)
978 break;
979
980 pr_notice("applying patch '%s' to loading module '%s'\n",
981 patch->mod->name, obj->mod->name);
982
983 ret = klp_pre_patch_callback(obj);
984 if (ret) {
985 pr_warn("pre-patch callback failed for object '%s'\n",
986 obj->name);
987 goto err;
988 }
989
990 ret = klp_patch_object(obj);
991 if (ret) {
992 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
993 patch->mod->name, obj->mod->name, ret);
994
995 klp_post_unpatch_callback(obj);
996 goto err;
997 }
998
999 if (patch != klp_transition_patch)
1000 klp_post_patch_callback(obj);
1001
1002 break;
1003 }
1004 }
1005
1006 mutex_unlock(&klp_mutex);
1007
1008 return 0;
1009
1010err:
1011 /*
1012 * If a patch is unsuccessfully applied, return
1013 * error to the module loader.
1014 */
1015 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1016 patch->mod->name, obj->mod->name, obj->mod->name);
1017 mod->klp_alive = false;
1018 klp_cleanup_module_patches_limited(mod, patch);
1019 mutex_unlock(&klp_mutex);
1020
1021 return ret;
1022}
1023
1024void klp_module_going(struct module *mod)
1025{
1026 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1027 mod->state != MODULE_STATE_COMING))
1028 return;
1029
1030 mutex_lock(&klp_mutex);
1031 /*
1032 * Each module has to know that klp_module_going()
1033 * has been called. We never know what module will
1034 * get patched by a new patch.
1035 */
1036 mod->klp_alive = false;
1037
1038 klp_cleanup_module_patches_limited(mod, NULL);
1039
1040 mutex_unlock(&klp_mutex);
1041}
1042
1043static int __init klp_init(void)
1044{
1045 int ret;
1046
1047 ret = klp_check_compiler_support();
1048 if (ret) {
1049 pr_info("Your compiler is too old; turning off.\n");
1050 return -EINVAL;
1051 }
1052
1053 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1054 if (!klp_root_kobj)
1055 return -ENOMEM;
1056
1057 return 0;
1058}
1059
1060module_init(klp_init);
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * core.c - Kernel Live Patching Core
4 *
5 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
6 * Copyright (C) 2014 SUSE
7 */
8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11#include <linux/module.h>
12#include <linux/kernel.h>
13#include <linux/mutex.h>
14#include <linux/slab.h>
15#include <linux/list.h>
16#include <linux/kallsyms.h>
17#include <linux/livepatch.h>
18#include <linux/elf.h>
19#include <linux/moduleloader.h>
20#include <linux/completion.h>
21#include <linux/memory.h>
22#include <linux/rcupdate.h>
23#include <asm/cacheflush.h>
24#include "core.h"
25#include "patch.h"
26#include "state.h"
27#include "transition.h"
28
29/*
30 * klp_mutex is a coarse lock which serializes access to klp data. All
31 * accesses to klp-related variables and structures must have mutex protection,
32 * except within the following functions which carefully avoid the need for it:
33 *
34 * - klp_ftrace_handler()
35 * - klp_update_patch_state()
36 * - __klp_sched_try_switch()
37 */
38DEFINE_MUTEX(klp_mutex);
39
40/*
41 * Actively used patches: enabled or in transition. Note that replaced
42 * or disabled patches are not listed even though the related kernel
43 * module still can be loaded.
44 */
45LIST_HEAD(klp_patches);
46
47static struct kobject *klp_root_kobj;
48
49static bool klp_is_module(struct klp_object *obj)
50{
51 return obj->name;
52}
53
54/* sets obj->mod if object is not vmlinux and module is found */
55static void klp_find_object_module(struct klp_object *obj)
56{
57 struct module *mod;
58
59 if (!klp_is_module(obj))
60 return;
61
62 rcu_read_lock_sched();
63 /*
64 * We do not want to block removal of patched modules and therefore
65 * we do not take a reference here. The patches are removed by
66 * klp_module_going() instead.
67 */
68 mod = find_module(obj->name);
69 /*
70 * Do not mess work of klp_module_coming() and klp_module_going().
71 * Note that the patch might still be needed before klp_module_going()
72 * is called. Module functions can be called even in the GOING state
73 * until mod->exit() finishes. This is especially important for
74 * patches that modify semantic of the functions.
75 */
76 if (mod && mod->klp_alive)
77 obj->mod = mod;
78
79 rcu_read_unlock_sched();
80}
81
82static bool klp_initialized(void)
83{
84 return !!klp_root_kobj;
85}
86
87static struct klp_func *klp_find_func(struct klp_object *obj,
88 struct klp_func *old_func)
89{
90 struct klp_func *func;
91
92 klp_for_each_func(obj, func) {
93 if ((strcmp(old_func->old_name, func->old_name) == 0) &&
94 (old_func->old_sympos == func->old_sympos)) {
95 return func;
96 }
97 }
98
99 return NULL;
100}
101
102static struct klp_object *klp_find_object(struct klp_patch *patch,
103 struct klp_object *old_obj)
104{
105 struct klp_object *obj;
106
107 klp_for_each_object(patch, obj) {
108 if (klp_is_module(old_obj)) {
109 if (klp_is_module(obj) &&
110 strcmp(old_obj->name, obj->name) == 0) {
111 return obj;
112 }
113 } else if (!klp_is_module(obj)) {
114 return obj;
115 }
116 }
117
118 return NULL;
119}
120
121struct klp_find_arg {
122 const char *name;
123 unsigned long addr;
124 unsigned long count;
125 unsigned long pos;
126};
127
128static int klp_match_callback(void *data, unsigned long addr)
129{
130 struct klp_find_arg *args = data;
131
132 args->addr = addr;
133 args->count++;
134
135 /*
136 * Finish the search when the symbol is found for the desired position
137 * or the position is not defined for a non-unique symbol.
138 */
139 if ((args->pos && (args->count == args->pos)) ||
140 (!args->pos && (args->count > 1)))
141 return 1;
142
143 return 0;
144}
145
146static int klp_find_callback(void *data, const char *name, unsigned long addr)
147{
148 struct klp_find_arg *args = data;
149
150 if (strcmp(args->name, name))
151 return 0;
152
153 return klp_match_callback(data, addr);
154}
155
156static int klp_find_object_symbol(const char *objname, const char *name,
157 unsigned long sympos, unsigned long *addr)
158{
159 struct klp_find_arg args = {
160 .name = name,
161 .addr = 0,
162 .count = 0,
163 .pos = sympos,
164 };
165
166 if (objname)
167 module_kallsyms_on_each_symbol(objname, klp_find_callback, &args);
168 else
169 kallsyms_on_each_match_symbol(klp_match_callback, name, &args);
170
171 /*
172 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
173 * otherwise ensure the symbol position count matches sympos.
174 */
175 if (args.addr == 0)
176 pr_err("symbol '%s' not found in symbol table\n", name);
177 else if (args.count > 1 && sympos == 0) {
178 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
179 name, objname);
180 } else if (sympos != args.count && sympos > 0) {
181 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
182 sympos, name, objname ? objname : "vmlinux");
183 } else {
184 *addr = args.addr;
185 return 0;
186 }
187
188 *addr = 0;
189 return -EINVAL;
190}
191
192static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
193 unsigned int symndx, Elf_Shdr *relasec,
194 const char *sec_objname)
195{
196 int i, cnt, ret;
197 char sym_objname[MODULE_NAME_LEN];
198 char sym_name[KSYM_NAME_LEN];
199 Elf_Rela *relas;
200 Elf_Sym *sym;
201 unsigned long sympos, addr;
202 bool sym_vmlinux;
203 bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
204
205 /*
206 * Since the field widths for sym_objname and sym_name in the sscanf()
207 * call are hard-coded and correspond to MODULE_NAME_LEN and
208 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
209 * and KSYM_NAME_LEN have the values we expect them to have.
210 *
211 * Because the value of MODULE_NAME_LEN can differ among architectures,
212 * we use the smallest/strictest upper bound possible (56, based on
213 * the current definition of MODULE_NAME_LEN) to prevent overflows.
214 */
215 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
216
217 relas = (Elf_Rela *) relasec->sh_addr;
218 /* For each rela in this klp relocation section */
219 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
220 sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
221 if (sym->st_shndx != SHN_LIVEPATCH) {
222 pr_err("symbol %s is not marked as a livepatch symbol\n",
223 strtab + sym->st_name);
224 return -EINVAL;
225 }
226
227 /* Format: .klp.sym.sym_objname.sym_name,sympos */
228 cnt = sscanf(strtab + sym->st_name,
229 ".klp.sym.%55[^.].%511[^,],%lu",
230 sym_objname, sym_name, &sympos);
231 if (cnt != 3) {
232 pr_err("symbol %s has an incorrectly formatted name\n",
233 strtab + sym->st_name);
234 return -EINVAL;
235 }
236
237 sym_vmlinux = !strcmp(sym_objname, "vmlinux");
238
239 /*
240 * Prevent module-specific KLP rela sections from referencing
241 * vmlinux symbols. This helps prevent ordering issues with
242 * module special section initializations. Presumably such
243 * symbols are exported and normal relas can be used instead.
244 */
245 if (!sec_vmlinux && sym_vmlinux) {
246 pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section\n",
247 sym_name);
248 return -EINVAL;
249 }
250
251 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
252 ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
253 sym_name, sympos, &addr);
254 if (ret)
255 return ret;
256
257 sym->st_value = addr;
258 }
259
260 return 0;
261}
262
263void __weak clear_relocate_add(Elf_Shdr *sechdrs,
264 const char *strtab,
265 unsigned int symindex,
266 unsigned int relsec,
267 struct module *me)
268{
269}
270
271/*
272 * At a high-level, there are two types of klp relocation sections: those which
273 * reference symbols which live in vmlinux; and those which reference symbols
274 * which live in other modules. This function is called for both types:
275 *
276 * 1) When a klp module itself loads, the module code calls this function to
277 * write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
278 * These relocations are written to the klp module text to allow the patched
279 * code/data to reference unexported vmlinux symbols. They're written as
280 * early as possible to ensure that other module init code (.e.g.,
281 * jump_label_apply_nops) can access any unexported vmlinux symbols which
282 * might be referenced by the klp module's special sections.
283 *
284 * 2) When a to-be-patched module loads -- or is already loaded when a
285 * corresponding klp module loads -- klp code calls this function to write
286 * module-specific klp relocations (.klp.rela.{module}.* sections). These
287 * are written to the klp module text to allow the patched code/data to
288 * reference symbols which live in the to-be-patched module or one of its
289 * module dependencies. Exported symbols are supported, in addition to
290 * unexported symbols, in order to enable late module patching, which allows
291 * the to-be-patched module to be loaded and patched sometime *after* the
292 * klp module is loaded.
293 */
294static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
295 const char *shstrtab, const char *strtab,
296 unsigned int symndx, unsigned int secndx,
297 const char *objname, bool apply)
298{
299 int cnt, ret;
300 char sec_objname[MODULE_NAME_LEN];
301 Elf_Shdr *sec = sechdrs + secndx;
302
303 /*
304 * Format: .klp.rela.sec_objname.section_name
305 * See comment in klp_resolve_symbols() for an explanation
306 * of the selected field width value.
307 */
308 cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
309 sec_objname);
310 if (cnt != 1) {
311 pr_err("section %s has an incorrectly formatted name\n",
312 shstrtab + sec->sh_name);
313 return -EINVAL;
314 }
315
316 if (strcmp(objname ? objname : "vmlinux", sec_objname))
317 return 0;
318
319 if (apply) {
320 ret = klp_resolve_symbols(sechdrs, strtab, symndx,
321 sec, sec_objname);
322 if (ret)
323 return ret;
324
325 return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
326 }
327
328 clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
329 return 0;
330}
331
332int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
333 const char *shstrtab, const char *strtab,
334 unsigned int symndx, unsigned int secndx,
335 const char *objname)
336{
337 return klp_write_section_relocs(pmod, sechdrs, shstrtab, strtab, symndx,
338 secndx, objname, true);
339}
340
341/*
342 * Sysfs Interface
343 *
344 * /sys/kernel/livepatch
345 * /sys/kernel/livepatch/<patch>
346 * /sys/kernel/livepatch/<patch>/enabled
347 * /sys/kernel/livepatch/<patch>/transition
348 * /sys/kernel/livepatch/<patch>/force
349 * /sys/kernel/livepatch/<patch>/<object>
350 * /sys/kernel/livepatch/<patch>/<object>/patched
351 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
352 */
353static int __klp_disable_patch(struct klp_patch *patch);
354
355static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
356 const char *buf, size_t count)
357{
358 struct klp_patch *patch;
359 int ret;
360 bool enabled;
361
362 ret = kstrtobool(buf, &enabled);
363 if (ret)
364 return ret;
365
366 patch = container_of(kobj, struct klp_patch, kobj);
367
368 mutex_lock(&klp_mutex);
369
370 if (patch->enabled == enabled) {
371 /* already in requested state */
372 ret = -EINVAL;
373 goto out;
374 }
375
376 /*
377 * Allow to reverse a pending transition in both ways. It might be
378 * necessary to complete the transition without forcing and breaking
379 * the system integrity.
380 *
381 * Do not allow to re-enable a disabled patch.
382 */
383 if (patch == klp_transition_patch)
384 klp_reverse_transition();
385 else if (!enabled)
386 ret = __klp_disable_patch(patch);
387 else
388 ret = -EINVAL;
389
390out:
391 mutex_unlock(&klp_mutex);
392
393 if (ret)
394 return ret;
395 return count;
396}
397
398static ssize_t enabled_show(struct kobject *kobj,
399 struct kobj_attribute *attr, char *buf)
400{
401 struct klp_patch *patch;
402
403 patch = container_of(kobj, struct klp_patch, kobj);
404 return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
405}
406
407static ssize_t transition_show(struct kobject *kobj,
408 struct kobj_attribute *attr, char *buf)
409{
410 struct klp_patch *patch;
411
412 patch = container_of(kobj, struct klp_patch, kobj);
413 return snprintf(buf, PAGE_SIZE-1, "%d\n",
414 patch == klp_transition_patch);
415}
416
417static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
418 const char *buf, size_t count)
419{
420 struct klp_patch *patch;
421 int ret;
422 bool val;
423
424 ret = kstrtobool(buf, &val);
425 if (ret)
426 return ret;
427
428 if (!val)
429 return count;
430
431 mutex_lock(&klp_mutex);
432
433 patch = container_of(kobj, struct klp_patch, kobj);
434 if (patch != klp_transition_patch) {
435 mutex_unlock(&klp_mutex);
436 return -EINVAL;
437 }
438
439 klp_force_transition();
440
441 mutex_unlock(&klp_mutex);
442
443 return count;
444}
445
446static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
447static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
448static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
449static struct attribute *klp_patch_attrs[] = {
450 &enabled_kobj_attr.attr,
451 &transition_kobj_attr.attr,
452 &force_kobj_attr.attr,
453 NULL
454};
455ATTRIBUTE_GROUPS(klp_patch);
456
457static ssize_t patched_show(struct kobject *kobj,
458 struct kobj_attribute *attr, char *buf)
459{
460 struct klp_object *obj;
461
462 obj = container_of(kobj, struct klp_object, kobj);
463 return sysfs_emit(buf, "%d\n", obj->patched);
464}
465
466static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched);
467static struct attribute *klp_object_attrs[] = {
468 &patched_kobj_attr.attr,
469 NULL,
470};
471ATTRIBUTE_GROUPS(klp_object);
472
473static void klp_free_object_dynamic(struct klp_object *obj)
474{
475 kfree(obj->name);
476 kfree(obj);
477}
478
479static void klp_init_func_early(struct klp_object *obj,
480 struct klp_func *func);
481static void klp_init_object_early(struct klp_patch *patch,
482 struct klp_object *obj);
483
484static struct klp_object *klp_alloc_object_dynamic(const char *name,
485 struct klp_patch *patch)
486{
487 struct klp_object *obj;
488
489 obj = kzalloc(sizeof(*obj), GFP_KERNEL);
490 if (!obj)
491 return NULL;
492
493 if (name) {
494 obj->name = kstrdup(name, GFP_KERNEL);
495 if (!obj->name) {
496 kfree(obj);
497 return NULL;
498 }
499 }
500
501 klp_init_object_early(patch, obj);
502 obj->dynamic = true;
503
504 return obj;
505}
506
507static void klp_free_func_nop(struct klp_func *func)
508{
509 kfree(func->old_name);
510 kfree(func);
511}
512
513static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
514 struct klp_object *obj)
515{
516 struct klp_func *func;
517
518 func = kzalloc(sizeof(*func), GFP_KERNEL);
519 if (!func)
520 return NULL;
521
522 if (old_func->old_name) {
523 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
524 if (!func->old_name) {
525 kfree(func);
526 return NULL;
527 }
528 }
529
530 klp_init_func_early(obj, func);
531 /*
532 * func->new_func is same as func->old_func. These addresses are
533 * set when the object is loaded, see klp_init_object_loaded().
534 */
535 func->old_sympos = old_func->old_sympos;
536 func->nop = true;
537
538 return func;
539}
540
541static int klp_add_object_nops(struct klp_patch *patch,
542 struct klp_object *old_obj)
543{
544 struct klp_object *obj;
545 struct klp_func *func, *old_func;
546
547 obj = klp_find_object(patch, old_obj);
548
549 if (!obj) {
550 obj = klp_alloc_object_dynamic(old_obj->name, patch);
551 if (!obj)
552 return -ENOMEM;
553 }
554
555 klp_for_each_func(old_obj, old_func) {
556 func = klp_find_func(obj, old_func);
557 if (func)
558 continue;
559
560 func = klp_alloc_func_nop(old_func, obj);
561 if (!func)
562 return -ENOMEM;
563 }
564
565 return 0;
566}
567
568/*
569 * Add 'nop' functions which simply return to the caller to run
570 * the original function. The 'nop' functions are added to a
571 * patch to facilitate a 'replace' mode.
572 */
573static int klp_add_nops(struct klp_patch *patch)
574{
575 struct klp_patch *old_patch;
576 struct klp_object *old_obj;
577
578 klp_for_each_patch(old_patch) {
579 klp_for_each_object(old_patch, old_obj) {
580 int err;
581
582 err = klp_add_object_nops(patch, old_obj);
583 if (err)
584 return err;
585 }
586 }
587
588 return 0;
589}
590
591static void klp_kobj_release_patch(struct kobject *kobj)
592{
593 struct klp_patch *patch;
594
595 patch = container_of(kobj, struct klp_patch, kobj);
596 complete(&patch->finish);
597}
598
599static const struct kobj_type klp_ktype_patch = {
600 .release = klp_kobj_release_patch,
601 .sysfs_ops = &kobj_sysfs_ops,
602 .default_groups = klp_patch_groups,
603};
604
605static void klp_kobj_release_object(struct kobject *kobj)
606{
607 struct klp_object *obj;
608
609 obj = container_of(kobj, struct klp_object, kobj);
610
611 if (obj->dynamic)
612 klp_free_object_dynamic(obj);
613}
614
615static const struct kobj_type klp_ktype_object = {
616 .release = klp_kobj_release_object,
617 .sysfs_ops = &kobj_sysfs_ops,
618 .default_groups = klp_object_groups,
619};
620
621static void klp_kobj_release_func(struct kobject *kobj)
622{
623 struct klp_func *func;
624
625 func = container_of(kobj, struct klp_func, kobj);
626
627 if (func->nop)
628 klp_free_func_nop(func);
629}
630
631static const struct kobj_type klp_ktype_func = {
632 .release = klp_kobj_release_func,
633 .sysfs_ops = &kobj_sysfs_ops,
634};
635
636static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
637{
638 struct klp_func *func, *tmp_func;
639
640 klp_for_each_func_safe(obj, func, tmp_func) {
641 if (nops_only && !func->nop)
642 continue;
643
644 list_del(&func->node);
645 kobject_put(&func->kobj);
646 }
647}
648
649/* Clean up when a patched object is unloaded */
650static void klp_free_object_loaded(struct klp_object *obj)
651{
652 struct klp_func *func;
653
654 obj->mod = NULL;
655
656 klp_for_each_func(obj, func) {
657 func->old_func = NULL;
658
659 if (func->nop)
660 func->new_func = NULL;
661 }
662}
663
664static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
665{
666 struct klp_object *obj, *tmp_obj;
667
668 klp_for_each_object_safe(patch, obj, tmp_obj) {
669 __klp_free_funcs(obj, nops_only);
670
671 if (nops_only && !obj->dynamic)
672 continue;
673
674 list_del(&obj->node);
675 kobject_put(&obj->kobj);
676 }
677}
678
679static void klp_free_objects(struct klp_patch *patch)
680{
681 __klp_free_objects(patch, false);
682}
683
684static void klp_free_objects_dynamic(struct klp_patch *patch)
685{
686 __klp_free_objects(patch, true);
687}
688
689/*
690 * This function implements the free operations that can be called safely
691 * under klp_mutex.
692 *
693 * The operation must be completed by calling klp_free_patch_finish()
694 * outside klp_mutex.
695 */
696static void klp_free_patch_start(struct klp_patch *patch)
697{
698 if (!list_empty(&patch->list))
699 list_del(&patch->list);
700
701 klp_free_objects(patch);
702}
703
704/*
705 * This function implements the free part that must be called outside
706 * klp_mutex.
707 *
708 * It must be called after klp_free_patch_start(). And it has to be
709 * the last function accessing the livepatch structures when the patch
710 * gets disabled.
711 */
712static void klp_free_patch_finish(struct klp_patch *patch)
713{
714 /*
715 * Avoid deadlock with enabled_store() sysfs callback by
716 * calling this outside klp_mutex. It is safe because
717 * this is called when the patch gets disabled and it
718 * cannot get enabled again.
719 */
720 kobject_put(&patch->kobj);
721 wait_for_completion(&patch->finish);
722
723 /* Put the module after the last access to struct klp_patch. */
724 if (!patch->forced)
725 module_put(patch->mod);
726}
727
728/*
729 * The livepatch might be freed from sysfs interface created by the patch.
730 * This work allows to wait until the interface is destroyed in a separate
731 * context.
732 */
733static void klp_free_patch_work_fn(struct work_struct *work)
734{
735 struct klp_patch *patch =
736 container_of(work, struct klp_patch, free_work);
737
738 klp_free_patch_finish(patch);
739}
740
741void klp_free_patch_async(struct klp_patch *patch)
742{
743 klp_free_patch_start(patch);
744 schedule_work(&patch->free_work);
745}
746
747void klp_free_replaced_patches_async(struct klp_patch *new_patch)
748{
749 struct klp_patch *old_patch, *tmp_patch;
750
751 klp_for_each_patch_safe(old_patch, tmp_patch) {
752 if (old_patch == new_patch)
753 return;
754 klp_free_patch_async(old_patch);
755 }
756}
757
758static int klp_init_func(struct klp_object *obj, struct klp_func *func)
759{
760 if (!func->old_name)
761 return -EINVAL;
762
763 /*
764 * NOPs get the address later. The patched module must be loaded,
765 * see klp_init_object_loaded().
766 */
767 if (!func->new_func && !func->nop)
768 return -EINVAL;
769
770 if (strlen(func->old_name) >= KSYM_NAME_LEN)
771 return -EINVAL;
772
773 INIT_LIST_HEAD(&func->stack_node);
774 func->patched = false;
775 func->transition = false;
776
777 /* The format for the sysfs directory is <function,sympos> where sympos
778 * is the nth occurrence of this symbol in kallsyms for the patched
779 * object. If the user selects 0 for old_sympos, then 1 will be used
780 * since a unique symbol will be the first occurrence.
781 */
782 return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
783 func->old_name,
784 func->old_sympos ? func->old_sympos : 1);
785}
786
787static int klp_write_object_relocs(struct klp_patch *patch,
788 struct klp_object *obj,
789 bool apply)
790{
791 int i, ret;
792 struct klp_modinfo *info = patch->mod->klp_info;
793
794 for (i = 1; i < info->hdr.e_shnum; i++) {
795 Elf_Shdr *sec = info->sechdrs + i;
796
797 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
798 continue;
799
800 ret = klp_write_section_relocs(patch->mod, info->sechdrs,
801 info->secstrings,
802 patch->mod->core_kallsyms.strtab,
803 info->symndx, i, obj->name, apply);
804 if (ret)
805 return ret;
806 }
807
808 return 0;
809}
810
811static int klp_apply_object_relocs(struct klp_patch *patch,
812 struct klp_object *obj)
813{
814 return klp_write_object_relocs(patch, obj, true);
815}
816
817static void klp_clear_object_relocs(struct klp_patch *patch,
818 struct klp_object *obj)
819{
820 klp_write_object_relocs(patch, obj, false);
821}
822
823/* parts of the initialization that is done only when the object is loaded */
824static int klp_init_object_loaded(struct klp_patch *patch,
825 struct klp_object *obj)
826{
827 struct klp_func *func;
828 int ret;
829
830 if (klp_is_module(obj)) {
831 /*
832 * Only write module-specific relocations here
833 * (.klp.rela.{module}.*). vmlinux-specific relocations were
834 * written earlier during the initialization of the klp module
835 * itself.
836 */
837 ret = klp_apply_object_relocs(patch, obj);
838 if (ret)
839 return ret;
840 }
841
842 klp_for_each_func(obj, func) {
843 ret = klp_find_object_symbol(obj->name, func->old_name,
844 func->old_sympos,
845 (unsigned long *)&func->old_func);
846 if (ret)
847 return ret;
848
849 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
850 &func->old_size, NULL);
851 if (!ret) {
852 pr_err("kallsyms size lookup failed for '%s'\n",
853 func->old_name);
854 return -ENOENT;
855 }
856
857 if (func->nop)
858 func->new_func = func->old_func;
859
860 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
861 &func->new_size, NULL);
862 if (!ret) {
863 pr_err("kallsyms size lookup failed for '%s' replacement\n",
864 func->old_name);
865 return -ENOENT;
866 }
867 }
868
869 return 0;
870}
871
872static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
873{
874 struct klp_func *func;
875 int ret;
876 const char *name;
877
878 if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
879 return -EINVAL;
880
881 obj->patched = false;
882 obj->mod = NULL;
883
884 klp_find_object_module(obj);
885
886 name = klp_is_module(obj) ? obj->name : "vmlinux";
887 ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
888 if (ret)
889 return ret;
890
891 klp_for_each_func(obj, func) {
892 ret = klp_init_func(obj, func);
893 if (ret)
894 return ret;
895 }
896
897 if (klp_is_object_loaded(obj))
898 ret = klp_init_object_loaded(patch, obj);
899
900 return ret;
901}
902
903static void klp_init_func_early(struct klp_object *obj,
904 struct klp_func *func)
905{
906 kobject_init(&func->kobj, &klp_ktype_func);
907 list_add_tail(&func->node, &obj->func_list);
908}
909
910static void klp_init_object_early(struct klp_patch *patch,
911 struct klp_object *obj)
912{
913 INIT_LIST_HEAD(&obj->func_list);
914 kobject_init(&obj->kobj, &klp_ktype_object);
915 list_add_tail(&obj->node, &patch->obj_list);
916}
917
918static void klp_init_patch_early(struct klp_patch *patch)
919{
920 struct klp_object *obj;
921 struct klp_func *func;
922
923 INIT_LIST_HEAD(&patch->list);
924 INIT_LIST_HEAD(&patch->obj_list);
925 kobject_init(&patch->kobj, &klp_ktype_patch);
926 patch->enabled = false;
927 patch->forced = false;
928 INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
929 init_completion(&patch->finish);
930
931 klp_for_each_object_static(patch, obj) {
932 klp_init_object_early(patch, obj);
933
934 klp_for_each_func_static(obj, func) {
935 klp_init_func_early(obj, func);
936 }
937 }
938}
939
940static int klp_init_patch(struct klp_patch *patch)
941{
942 struct klp_object *obj;
943 int ret;
944
945 ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
946 if (ret)
947 return ret;
948
949 if (patch->replace) {
950 ret = klp_add_nops(patch);
951 if (ret)
952 return ret;
953 }
954
955 klp_for_each_object(patch, obj) {
956 ret = klp_init_object(patch, obj);
957 if (ret)
958 return ret;
959 }
960
961 list_add_tail(&patch->list, &klp_patches);
962
963 return 0;
964}
965
966static int __klp_disable_patch(struct klp_patch *patch)
967{
968 struct klp_object *obj;
969
970 if (WARN_ON(!patch->enabled))
971 return -EINVAL;
972
973 if (klp_transition_patch)
974 return -EBUSY;
975
976 klp_init_transition(patch, KLP_UNPATCHED);
977
978 klp_for_each_object(patch, obj)
979 if (obj->patched)
980 klp_pre_unpatch_callback(obj);
981
982 /*
983 * Enforce the order of the func->transition writes in
984 * klp_init_transition() and the TIF_PATCH_PENDING writes in
985 * klp_start_transition(). In the rare case where klp_ftrace_handler()
986 * is called shortly after klp_update_patch_state() switches the task,
987 * this ensures the handler sees that func->transition is set.
988 */
989 smp_wmb();
990
991 klp_start_transition();
992 patch->enabled = false;
993 klp_try_complete_transition();
994
995 return 0;
996}
997
998static int __klp_enable_patch(struct klp_patch *patch)
999{
1000 struct klp_object *obj;
1001 int ret;
1002
1003 if (klp_transition_patch)
1004 return -EBUSY;
1005
1006 if (WARN_ON(patch->enabled))
1007 return -EINVAL;
1008
1009 pr_notice("enabling patch '%s'\n", patch->mod->name);
1010
1011 klp_init_transition(patch, KLP_PATCHED);
1012
1013 /*
1014 * Enforce the order of the func->transition writes in
1015 * klp_init_transition() and the ops->func_stack writes in
1016 * klp_patch_object(), so that klp_ftrace_handler() will see the
1017 * func->transition updates before the handler is registered and the
1018 * new funcs become visible to the handler.
1019 */
1020 smp_wmb();
1021
1022 klp_for_each_object(patch, obj) {
1023 if (!klp_is_object_loaded(obj))
1024 continue;
1025
1026 ret = klp_pre_patch_callback(obj);
1027 if (ret) {
1028 pr_warn("pre-patch callback failed for object '%s'\n",
1029 klp_is_module(obj) ? obj->name : "vmlinux");
1030 goto err;
1031 }
1032
1033 ret = klp_patch_object(obj);
1034 if (ret) {
1035 pr_warn("failed to patch object '%s'\n",
1036 klp_is_module(obj) ? obj->name : "vmlinux");
1037 goto err;
1038 }
1039 }
1040
1041 klp_start_transition();
1042 patch->enabled = true;
1043 klp_try_complete_transition();
1044
1045 return 0;
1046err:
1047 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
1048
1049 klp_cancel_transition();
1050 return ret;
1051}
1052
1053/**
1054 * klp_enable_patch() - enable the livepatch
1055 * @patch: patch to be enabled
1056 *
1057 * Initializes the data structure associated with the patch, creates the sysfs
1058 * interface, performs the needed symbol lookups and code relocations,
1059 * registers the patched functions with ftrace.
1060 *
1061 * This function is supposed to be called from the livepatch module_init()
1062 * callback.
1063 *
1064 * Return: 0 on success, otherwise error
1065 */
1066int klp_enable_patch(struct klp_patch *patch)
1067{
1068 int ret;
1069 struct klp_object *obj;
1070
1071 if (!patch || !patch->mod || !patch->objs)
1072 return -EINVAL;
1073
1074 klp_for_each_object_static(patch, obj) {
1075 if (!obj->funcs)
1076 return -EINVAL;
1077 }
1078
1079
1080 if (!is_livepatch_module(patch->mod)) {
1081 pr_err("module %s is not marked as a livepatch module\n",
1082 patch->mod->name);
1083 return -EINVAL;
1084 }
1085
1086 if (!klp_initialized())
1087 return -ENODEV;
1088
1089 if (!klp_have_reliable_stack()) {
1090 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
1091 pr_warn("The livepatch transition may never complete.\n");
1092 }
1093
1094 mutex_lock(&klp_mutex);
1095
1096 if (!klp_is_patch_compatible(patch)) {
1097 pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
1098 patch->mod->name);
1099 mutex_unlock(&klp_mutex);
1100 return -EINVAL;
1101 }
1102
1103 if (!try_module_get(patch->mod)) {
1104 mutex_unlock(&klp_mutex);
1105 return -ENODEV;
1106 }
1107
1108 klp_init_patch_early(patch);
1109
1110 ret = klp_init_patch(patch);
1111 if (ret)
1112 goto err;
1113
1114 ret = __klp_enable_patch(patch);
1115 if (ret)
1116 goto err;
1117
1118 mutex_unlock(&klp_mutex);
1119
1120 return 0;
1121
1122err:
1123 klp_free_patch_start(patch);
1124
1125 mutex_unlock(&klp_mutex);
1126
1127 klp_free_patch_finish(patch);
1128
1129 return ret;
1130}
1131EXPORT_SYMBOL_GPL(klp_enable_patch);
1132
1133/*
1134 * This function unpatches objects from the replaced livepatches.
1135 *
1136 * We could be pretty aggressive here. It is called in the situation where
1137 * these structures are no longer accessed from the ftrace handler.
1138 * All functions are redirected by the klp_transition_patch. They
1139 * use either a new code or they are in the original code because
1140 * of the special nop function patches.
1141 *
1142 * The only exception is when the transition was forced. In this case,
1143 * klp_ftrace_handler() might still see the replaced patch on the stack.
1144 * Fortunately, it is carefully designed to work with removed functions
1145 * thanks to RCU. We only have to keep the patches on the system. Also
1146 * this is handled transparently by patch->module_put.
1147 */
1148void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
1149{
1150 struct klp_patch *old_patch;
1151
1152 klp_for_each_patch(old_patch) {
1153 if (old_patch == new_patch)
1154 return;
1155
1156 old_patch->enabled = false;
1157 klp_unpatch_objects(old_patch);
1158 }
1159}
1160
1161/*
1162 * This function removes the dynamically allocated 'nop' functions.
1163 *
1164 * We could be pretty aggressive. NOPs do not change the existing
1165 * behavior except for adding unnecessary delay by the ftrace handler.
1166 *
1167 * It is safe even when the transition was forced. The ftrace handler
1168 * will see a valid ops->func_stack entry thanks to RCU.
1169 *
1170 * We could even free the NOPs structures. They must be the last entry
1171 * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1172 * It does the same as klp_synchronize_transition() to make sure that
1173 * nobody is inside the ftrace handler once the operation finishes.
1174 *
1175 * IMPORTANT: It must be called right after removing the replaced patches!
1176 */
1177void klp_discard_nops(struct klp_patch *new_patch)
1178{
1179 klp_unpatch_objects_dynamic(klp_transition_patch);
1180 klp_free_objects_dynamic(klp_transition_patch);
1181}
1182
1183/*
1184 * Remove parts of patches that touch a given kernel module. The list of
1185 * patches processed might be limited. When limit is NULL, all patches
1186 * will be handled.
1187 */
1188static void klp_cleanup_module_patches_limited(struct module *mod,
1189 struct klp_patch *limit)
1190{
1191 struct klp_patch *patch;
1192 struct klp_object *obj;
1193
1194 klp_for_each_patch(patch) {
1195 if (patch == limit)
1196 break;
1197
1198 klp_for_each_object(patch, obj) {
1199 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1200 continue;
1201
1202 if (patch != klp_transition_patch)
1203 klp_pre_unpatch_callback(obj);
1204
1205 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1206 patch->mod->name, obj->mod->name);
1207 klp_unpatch_object(obj);
1208
1209 klp_post_unpatch_callback(obj);
1210 klp_clear_object_relocs(patch, obj);
1211 klp_free_object_loaded(obj);
1212 break;
1213 }
1214 }
1215}
1216
1217int klp_module_coming(struct module *mod)
1218{
1219 int ret;
1220 struct klp_patch *patch;
1221 struct klp_object *obj;
1222
1223 if (WARN_ON(mod->state != MODULE_STATE_COMING))
1224 return -EINVAL;
1225
1226 if (!strcmp(mod->name, "vmlinux")) {
1227 pr_err("vmlinux.ko: invalid module name\n");
1228 return -EINVAL;
1229 }
1230
1231 mutex_lock(&klp_mutex);
1232 /*
1233 * Each module has to know that klp_module_coming()
1234 * has been called. We never know what module will
1235 * get patched by a new patch.
1236 */
1237 mod->klp_alive = true;
1238
1239 klp_for_each_patch(patch) {
1240 klp_for_each_object(patch, obj) {
1241 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1242 continue;
1243
1244 obj->mod = mod;
1245
1246 ret = klp_init_object_loaded(patch, obj);
1247 if (ret) {
1248 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1249 patch->mod->name, obj->mod->name, ret);
1250 goto err;
1251 }
1252
1253 pr_notice("applying patch '%s' to loading module '%s'\n",
1254 patch->mod->name, obj->mod->name);
1255
1256 ret = klp_pre_patch_callback(obj);
1257 if (ret) {
1258 pr_warn("pre-patch callback failed for object '%s'\n",
1259 obj->name);
1260 goto err;
1261 }
1262
1263 ret = klp_patch_object(obj);
1264 if (ret) {
1265 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1266 patch->mod->name, obj->mod->name, ret);
1267
1268 klp_post_unpatch_callback(obj);
1269 goto err;
1270 }
1271
1272 if (patch != klp_transition_patch)
1273 klp_post_patch_callback(obj);
1274
1275 break;
1276 }
1277 }
1278
1279 mutex_unlock(&klp_mutex);
1280
1281 return 0;
1282
1283err:
1284 /*
1285 * If a patch is unsuccessfully applied, return
1286 * error to the module loader.
1287 */
1288 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1289 patch->mod->name, obj->mod->name, obj->mod->name);
1290 mod->klp_alive = false;
1291 obj->mod = NULL;
1292 klp_cleanup_module_patches_limited(mod, patch);
1293 mutex_unlock(&klp_mutex);
1294
1295 return ret;
1296}
1297
1298void klp_module_going(struct module *mod)
1299{
1300 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1301 mod->state != MODULE_STATE_COMING))
1302 return;
1303
1304 mutex_lock(&klp_mutex);
1305 /*
1306 * Each module has to know that klp_module_going()
1307 * has been called. We never know what module will
1308 * get patched by a new patch.
1309 */
1310 mod->klp_alive = false;
1311
1312 klp_cleanup_module_patches_limited(mod, NULL);
1313
1314 mutex_unlock(&klp_mutex);
1315}
1316
1317static int __init klp_init(void)
1318{
1319 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1320 if (!klp_root_kobj)
1321 return -ENOMEM;
1322
1323 return 0;
1324}
1325
1326module_init(klp_init);