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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * core.c - Kernel Live Patching Core
4 *
5 * Copyright (C) 2014 Seth Jennings <[email protected]>
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 guard(rcu)();
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
80static bool klp_initialized(void)
81{
82 return !!klp_root_kobj;
83}
84
85static struct klp_func *klp_find_func(struct klp_object *obj,
86 struct klp_func *old_func)
87{
88 struct klp_func *func;
89
90 klp_for_each_func(obj, func) {
91 /*
92 * Besides identical old_sympos, also consider old_sympos
93 * of 0 and 1 are identical.
94 */
95 if ((strcmp(old_func->old_name, func->old_name) == 0) &&
96 ((old_func->old_sympos == func->old_sympos) ||
97 (old_func->old_sympos == 0 && func->old_sympos == 1) ||
98 (old_func->old_sympos == 1 && func->old_sympos == 0))) {
99 return func;
100 }
101 }
102
103 return NULL;
104}
105
106static struct klp_object *klp_find_object(struct klp_patch *patch,
107 struct klp_object *old_obj)
108{
109 struct klp_object *obj;
110
111 klp_for_each_object(patch, obj) {
112 if (klp_is_module(old_obj)) {
113 if (klp_is_module(obj) &&
114 strcmp(old_obj->name, obj->name) == 0) {
115 return obj;
116 }
117 } else if (!klp_is_module(obj)) {
118 return obj;
119 }
120 }
121
122 return NULL;
123}
124
125struct klp_find_arg {
126 const char *name;
127 unsigned long addr;
128 unsigned long count;
129 unsigned long pos;
130};
131
132static int klp_match_callback(void *data, unsigned long addr)
133{
134 struct klp_find_arg *args = data;
135
136 args->addr = addr;
137 args->count++;
138
139 /*
140 * Finish the search when the symbol is found for the desired position
141 * or the position is not defined for a non-unique symbol.
142 */
143 if ((args->pos && (args->count == args->pos)) ||
144 (!args->pos && (args->count > 1)))
145 return 1;
146
147 return 0;
148}
149
150static int klp_find_callback(void *data, const char *name, unsigned long addr)
151{
152 struct klp_find_arg *args = data;
153
154 if (strcmp(args->name, name))
155 return 0;
156
157 return klp_match_callback(data, addr);
158}
159
160static int klp_find_object_symbol(const char *objname, const char *name,
161 unsigned long sympos, unsigned long *addr)
162{
163 struct klp_find_arg args = {
164 .name = name,
165 .addr = 0,
166 .count = 0,
167 .pos = sympos,
168 };
169
170 if (objname)
171 module_kallsyms_on_each_symbol(objname, klp_find_callback, &args);
172 else
173 kallsyms_on_each_match_symbol(klp_match_callback, name, &args);
174
175 /*
176 * Ensure an address was found. If sympos is 0, ensure symbol is unique;
177 * otherwise ensure the symbol position count matches sympos.
178 */
179 if (args.addr == 0)
180 pr_err("symbol '%s' not found in symbol table\n", name);
181 else if (args.count > 1 && sympos == 0) {
182 pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
183 name, objname);
184 } else if (sympos != args.count && sympos > 0) {
185 pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
186 sympos, name, objname ? objname : "vmlinux");
187 } else {
188 *addr = args.addr;
189 return 0;
190 }
191
192 *addr = 0;
193 return -EINVAL;
194}
195
196static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
197 unsigned int symndx, Elf_Shdr *relasec,
198 const char *sec_objname)
199{
200 int i, cnt, ret;
201 char sym_objname[MODULE_NAME_LEN];
202 char sym_name[KSYM_NAME_LEN];
203 Elf_Rela *relas;
204 Elf_Sym *sym;
205 unsigned long sympos, addr;
206 bool sym_vmlinux;
207 bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
208
209 /*
210 * Since the field widths for sym_objname and sym_name in the sscanf()
211 * call are hard-coded and correspond to MODULE_NAME_LEN and
212 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
213 * and KSYM_NAME_LEN have the values we expect them to have.
214 *
215 * Because the value of MODULE_NAME_LEN can differ among architectures,
216 * we use the smallest/strictest upper bound possible (56, based on
217 * the current definition of MODULE_NAME_LEN) to prevent overflows.
218 */
219 BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 512);
220
221 relas = (Elf_Rela *) relasec->sh_addr;
222 /* For each rela in this klp relocation section */
223 for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
224 sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
225 if (sym->st_shndx != SHN_LIVEPATCH) {
226 pr_err("symbol %s at rela sec %u idx %d is not marked as a livepatch symbol\n",
227 strtab + sym->st_name, symndx, i);
228 return -EINVAL;
229 }
230
231 /* Format: .klp.sym.sym_objname.sym_name,sympos */
232 cnt = sscanf(strtab + sym->st_name,
233 KLP_SYM_PREFIX "%55[^.].%511[^,],%lu",
234 sym_objname, sym_name, &sympos);
235 if (cnt != 3) {
236 pr_err("symbol %s has an incorrectly formatted name\n",
237 strtab + sym->st_name);
238 return -EINVAL;
239 }
240
241 sym_vmlinux = !strcmp(sym_objname, "vmlinux");
242
243 /*
244 * Prevent module-specific KLP rela sections from referencing
245 * vmlinux symbols. This helps prevent ordering issues with
246 * module special section initializations. Presumably such
247 * symbols are exported and normal relas can be used instead.
248 */
249 if (!sec_vmlinux && sym_vmlinux) {
250 pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section\n",
251 sym_name);
252 return -EINVAL;
253 }
254
255 /* klp_find_object_symbol() treats a NULL objname as vmlinux */
256 ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
257 sym_name, sympos, &addr);
258 if (ret)
259 return ret;
260
261 sym->st_value = addr;
262 }
263
264 return 0;
265}
266
267void __weak clear_relocate_add(Elf_Shdr *sechdrs,
268 const char *strtab,
269 unsigned int symindex,
270 unsigned int relsec,
271 struct module *me)
272{
273}
274
275/*
276 * At a high-level, there are two types of klp relocation sections: those which
277 * reference symbols which live in vmlinux; and those which reference symbols
278 * which live in other modules. This function is called for both types:
279 *
280 * 1) When a klp module itself loads, the module code calls this function to
281 * write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
282 * These relocations are written to the klp module text to allow the patched
283 * code/data to reference unexported vmlinux symbols. They're written as
284 * early as possible to ensure that other module init code (.e.g.,
285 * jump_label_apply_nops) can access any unexported vmlinux symbols which
286 * might be referenced by the klp module's special sections.
287 *
288 * 2) When a to-be-patched module loads -- or is already loaded when a
289 * corresponding klp module loads -- klp code calls this function to write
290 * module-specific klp relocations (.klp.rela.{module}.* sections). These
291 * are written to the klp module text to allow the patched code/data to
292 * reference symbols which live in the to-be-patched module or one of its
293 * module dependencies. Exported symbols are supported, in addition to
294 * unexported symbols, in order to enable late module patching, which allows
295 * the to-be-patched module to be loaded and patched sometime *after* the
296 * klp module is loaded.
297 */
298static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
299 const char *shstrtab, const char *strtab,
300 unsigned int symndx, unsigned int secndx,
301 const char *objname, bool apply)
302{
303 int cnt, ret;
304 char sec_objname[MODULE_NAME_LEN];
305 Elf_Shdr *sec = sechdrs + secndx;
306
307 /*
308 * Format: .klp.rela.sec_objname.section_name
309 * See comment in klp_resolve_symbols() for an explanation
310 * of the selected field width value.
311 */
312 cnt = sscanf(shstrtab + sec->sh_name, KLP_RELOC_SEC_PREFIX "%55[^.]",
313 sec_objname);
314 if (cnt != 1) {
315 pr_err("section %s has an incorrectly formatted name\n",
316 shstrtab + sec->sh_name);
317 return -EINVAL;
318 }
319
320 if (strcmp(objname ? objname : "vmlinux", sec_objname))
321 return 0;
322
323 if (apply) {
324 ret = klp_resolve_symbols(sechdrs, strtab, symndx,
325 sec, sec_objname);
326 if (ret)
327 return ret;
328
329 return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
330 }
331
332 clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
333 return 0;
334}
335
336int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
337 const char *shstrtab, const char *strtab,
338 unsigned int symndx, unsigned int secndx,
339 const char *objname)
340{
341 return klp_write_section_relocs(pmod, sechdrs, shstrtab, strtab, symndx,
342 secndx, objname, true);
343}
344
345/*
346 * Sysfs Interface
347 *
348 * /sys/kernel/livepatch
349 * /sys/kernel/livepatch/<patch>
350 * /sys/kernel/livepatch/<patch>/enabled
351 * /sys/kernel/livepatch/<patch>/transition
352 * /sys/kernel/livepatch/<patch>/force
353 * /sys/kernel/livepatch/<patch>/replace
354 * /sys/kernel/livepatch/<patch>/stack_order
355 * /sys/kernel/livepatch/<patch>/<object>
356 * /sys/kernel/livepatch/<patch>/<object>/patched
357 * /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
358 */
359static int __klp_disable_patch(struct klp_patch *patch);
360
361static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
362 const char *buf, size_t count)
363{
364 struct klp_patch *patch;
365 int ret;
366 bool enabled;
367
368 ret = kstrtobool(buf, &enabled);
369 if (ret)
370 return ret;
371
372 patch = container_of(kobj, struct klp_patch, kobj);
373
374 mutex_lock(&klp_mutex);
375
376 if (patch->enabled == enabled) {
377 /* already in requested state */
378 ret = -EINVAL;
379 goto out;
380 }
381
382 /*
383 * Allow to reverse a pending transition in both ways. It might be
384 * necessary to complete the transition without forcing and breaking
385 * the system integrity.
386 *
387 * Do not allow to re-enable a disabled patch.
388 */
389 if (patch == klp_transition_patch)
390 klp_reverse_transition();
391 else if (!enabled)
392 ret = __klp_disable_patch(patch);
393 else
394 ret = -EINVAL;
395
396out:
397 mutex_unlock(&klp_mutex);
398
399 if (ret)
400 return ret;
401 return count;
402}
403
404static ssize_t enabled_show(struct kobject *kobj,
405 struct kobj_attribute *attr, char *buf)
406{
407 struct klp_patch *patch;
408
409 patch = container_of(kobj, struct klp_patch, kobj);
410 return sysfs_emit(buf, "%d\n", patch->enabled);
411}
412
413static ssize_t transition_show(struct kobject *kobj,
414 struct kobj_attribute *attr, char *buf)
415{
416 struct klp_patch *patch;
417
418 patch = container_of(kobj, struct klp_patch, kobj);
419 return sysfs_emit(buf, "%d\n", patch == klp_transition_patch);
420}
421
422static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
423 const char *buf, size_t count)
424{
425 struct klp_patch *patch;
426 int ret;
427 bool val;
428
429 ret = kstrtobool(buf, &val);
430 if (ret)
431 return ret;
432
433 if (!val)
434 return count;
435
436 mutex_lock(&klp_mutex);
437
438 patch = container_of(kobj, struct klp_patch, kobj);
439 if (patch != klp_transition_patch) {
440 mutex_unlock(&klp_mutex);
441 return -EINVAL;
442 }
443
444 klp_force_transition();
445
446 mutex_unlock(&klp_mutex);
447
448 return count;
449}
450
451static ssize_t replace_show(struct kobject *kobj,
452 struct kobj_attribute *attr, char *buf)
453{
454 struct klp_patch *patch;
455
456 patch = container_of(kobj, struct klp_patch, kobj);
457 return sysfs_emit(buf, "%d\n", patch->replace);
458}
459
460static ssize_t stack_order_show(struct kobject *kobj,
461 struct kobj_attribute *attr, char *buf)
462{
463 struct klp_patch *patch, *this_patch;
464 int stack_order = 0;
465
466 this_patch = container_of(kobj, struct klp_patch, kobj);
467
468 mutex_lock(&klp_mutex);
469
470 klp_for_each_patch(patch) {
471 stack_order++;
472 if (patch == this_patch)
473 break;
474 }
475
476 mutex_unlock(&klp_mutex);
477
478 return sysfs_emit(buf, "%d\n", stack_order);
479}
480
481static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
482static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
483static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
484static struct kobj_attribute replace_kobj_attr = __ATTR_RO(replace);
485static struct kobj_attribute stack_order_kobj_attr = __ATTR_RO(stack_order);
486static struct attribute *klp_patch_attrs[] = {
487 &enabled_kobj_attr.attr,
488 &transition_kobj_attr.attr,
489 &force_kobj_attr.attr,
490 &replace_kobj_attr.attr,
491 &stack_order_kobj_attr.attr,
492 NULL
493};
494ATTRIBUTE_GROUPS(klp_patch);
495
496static ssize_t patched_show(struct kobject *kobj,
497 struct kobj_attribute *attr, char *buf)
498{
499 struct klp_object *obj;
500
501 obj = container_of(kobj, struct klp_object, kobj);
502 return sysfs_emit(buf, "%d\n", obj->patched);
503}
504
505static struct kobj_attribute patched_kobj_attr = __ATTR_RO(patched);
506static struct attribute *klp_object_attrs[] = {
507 &patched_kobj_attr.attr,
508 NULL,
509};
510ATTRIBUTE_GROUPS(klp_object);
511
512static void klp_free_object_dynamic(struct klp_object *obj)
513{
514 kfree(obj->name);
515 kfree(obj);
516}
517
518static void klp_init_func_early(struct klp_object *obj,
519 struct klp_func *func);
520static void klp_init_object_early(struct klp_patch *patch,
521 struct klp_object *obj);
522
523static struct klp_object *klp_alloc_object_dynamic(const char *name,
524 struct klp_patch *patch)
525{
526 struct klp_object *obj;
527
528 obj = kzalloc_obj(*obj);
529 if (!obj)
530 return NULL;
531
532 if (name) {
533 obj->name = kstrdup(name, GFP_KERNEL);
534 if (!obj->name) {
535 kfree(obj);
536 return NULL;
537 }
538 }
539
540 klp_init_object_early(patch, obj);
541 obj->dynamic = true;
542
543 return obj;
544}
545
546static void klp_free_func_nop(struct klp_func *func)
547{
548 kfree(func->old_name);
549 kfree(func);
550}
551
552static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
553 struct klp_object *obj)
554{
555 struct klp_func *func;
556
557 func = kzalloc_obj(*func);
558 if (!func)
559 return NULL;
560
561 if (old_func->old_name) {
562 func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
563 if (!func->old_name) {
564 kfree(func);
565 return NULL;
566 }
567 }
568
569 klp_init_func_early(obj, func);
570 /*
571 * func->new_func is same as func->old_func. These addresses are
572 * set when the object is loaded, see klp_init_object_loaded().
573 */
574 func->old_sympos = old_func->old_sympos;
575 func->nop = true;
576
577 return func;
578}
579
580static int klp_add_object_nops(struct klp_patch *patch,
581 struct klp_object *old_obj)
582{
583 struct klp_object *obj;
584 struct klp_func *func, *old_func;
585
586 obj = klp_find_object(patch, old_obj);
587
588 if (!obj) {
589 obj = klp_alloc_object_dynamic(old_obj->name, patch);
590 if (!obj)
591 return -ENOMEM;
592 }
593
594 klp_for_each_func(old_obj, old_func) {
595 func = klp_find_func(obj, old_func);
596 if (func)
597 continue;
598
599 func = klp_alloc_func_nop(old_func, obj);
600 if (!func)
601 return -ENOMEM;
602 }
603
604 return 0;
605}
606
607/*
608 * Add 'nop' functions which simply return to the caller to run the
609 * original function.
610 *
611 * They are added only when the atomic replace mode is used and only for
612 * functions which are currently livepatched but are no longer included
613 * in the new livepatch.
614 */
615static int klp_add_nops(struct klp_patch *patch)
616{
617 struct klp_patch *old_patch;
618 struct klp_object *old_obj;
619
620 klp_for_each_patch(old_patch) {
621 klp_for_each_object(old_patch, old_obj) {
622 int err;
623
624 err = klp_add_object_nops(patch, old_obj);
625 if (err)
626 return err;
627 }
628 }
629
630 return 0;
631}
632
633static void klp_kobj_release_patch(struct kobject *kobj)
634{
635 struct klp_patch *patch;
636
637 patch = container_of(kobj, struct klp_patch, kobj);
638 complete(&patch->finish);
639}
640
641static const struct kobj_type klp_ktype_patch = {
642 .release = klp_kobj_release_patch,
643 .sysfs_ops = &kobj_sysfs_ops,
644 .default_groups = klp_patch_groups,
645};
646
647static void klp_kobj_release_object(struct kobject *kobj)
648{
649 struct klp_object *obj;
650
651 obj = container_of(kobj, struct klp_object, kobj);
652
653 if (obj->dynamic)
654 klp_free_object_dynamic(obj);
655}
656
657static const struct kobj_type klp_ktype_object = {
658 .release = klp_kobj_release_object,
659 .sysfs_ops = &kobj_sysfs_ops,
660 .default_groups = klp_object_groups,
661};
662
663static void klp_kobj_release_func(struct kobject *kobj)
664{
665 struct klp_func *func;
666
667 func = container_of(kobj, struct klp_func, kobj);
668
669 if (func->nop)
670 klp_free_func_nop(func);
671}
672
673static const struct kobj_type klp_ktype_func = {
674 .release = klp_kobj_release_func,
675 .sysfs_ops = &kobj_sysfs_ops,
676};
677
678static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
679{
680 struct klp_func *func, *tmp_func;
681
682 klp_for_each_func_safe(obj, func, tmp_func) {
683 if (nops_only && !func->nop)
684 continue;
685
686 list_del(&func->node);
687 kobject_put(&func->kobj);
688 }
689}
690
691/* Clean up when a patched object is unloaded */
692static void klp_free_object_loaded(struct klp_object *obj)
693{
694 struct klp_func *func;
695
696 obj->mod = NULL;
697
698 klp_for_each_func(obj, func) {
699 func->old_func = NULL;
700
701 if (func->nop)
702 func->new_func = NULL;
703 }
704}
705
706static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
707{
708 struct klp_object *obj, *tmp_obj;
709
710 klp_for_each_object_safe(patch, obj, tmp_obj) {
711 __klp_free_funcs(obj, nops_only);
712
713 if (nops_only && !obj->dynamic)
714 continue;
715
716 list_del(&obj->node);
717 kobject_put(&obj->kobj);
718 }
719}
720
721static void klp_free_objects(struct klp_patch *patch)
722{
723 __klp_free_objects(patch, false);
724}
725
726static void klp_free_objects_dynamic(struct klp_patch *patch)
727{
728 __klp_free_objects(patch, true);
729}
730
731/*
732 * This function implements the free operations that can be called safely
733 * under klp_mutex.
734 *
735 * The operation must be completed by calling klp_free_patch_finish()
736 * outside klp_mutex.
737 */
738static void klp_free_patch_start(struct klp_patch *patch)
739{
740 if (!list_empty(&patch->list))
741 list_del(&patch->list);
742
743 klp_free_objects(patch);
744}
745
746/*
747 * This function implements the free part that must be called outside
748 * klp_mutex.
749 *
750 * It must be called after klp_free_patch_start(). And it has to be
751 * the last function accessing the livepatch structures when the patch
752 * gets disabled.
753 */
754static void klp_free_patch_finish(struct klp_patch *patch)
755{
756 /*
757 * Avoid deadlock with enabled_store() sysfs callback by
758 * calling this outside klp_mutex. It is safe because
759 * this is called when the patch gets disabled and it
760 * cannot get enabled again.
761 */
762 kobject_put(&patch->kobj);
763 wait_for_completion(&patch->finish);
764
765 /* Put the module after the last access to struct klp_patch. */
766 if (!patch->forced)
767 module_put(patch->mod);
768}
769
770/*
771 * The livepatch might be freed from sysfs interface created by the patch.
772 * This work allows to wait until the interface is destroyed in a separate
773 * context.
774 */
775static void klp_free_patch_work_fn(struct work_struct *work)
776{
777 struct klp_patch *patch =
778 container_of(work, struct klp_patch, free_work);
779
780 klp_free_patch_finish(patch);
781}
782
783void klp_free_patch_async(struct klp_patch *patch)
784{
785 klp_free_patch_start(patch);
786 schedule_work(&patch->free_work);
787}
788
789void klp_free_replaced_patches_async(struct klp_patch *new_patch)
790{
791 struct klp_patch *old_patch, *tmp_patch;
792
793 klp_for_each_patch_safe(old_patch, tmp_patch) {
794 if (old_patch == new_patch)
795 return;
796 klp_free_patch_async(old_patch);
797 }
798}
799
800static int klp_init_func(struct klp_object *obj, struct klp_func *func)
801{
802 /*
803 * NOPs get the address later. The patched module must be loaded,
804 * see klp_init_object_loaded().
805 */
806 if (!func->new_func && !func->nop)
807 return -EINVAL;
808
809 if (strlen(func->old_name) >= KSYM_NAME_LEN)
810 return -EINVAL;
811
812 INIT_LIST_HEAD(&func->stack_node);
813 func->patched = false;
814 func->transition = false;
815
816 /* The format for the sysfs directory is <function,sympos> where sympos
817 * is the nth occurrence of this symbol in kallsyms for the patched
818 * object. If the user selects 0 for old_sympos, then 1 will be used
819 * since a unique symbol will be the first occurrence.
820 */
821 return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
822 func->old_name,
823 func->old_sympos ? func->old_sympos : 1);
824}
825
826static int klp_write_object_relocs(struct klp_patch *patch,
827 struct klp_object *obj,
828 bool apply)
829{
830 int i, ret;
831 struct klp_modinfo *info = patch->mod->klp_info;
832
833 for (i = 1; i < info->hdr.e_shnum; i++) {
834 Elf_Shdr *sec = info->sechdrs + i;
835
836 if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
837 continue;
838
839 ret = klp_write_section_relocs(patch->mod, info->sechdrs,
840 info->secstrings,
841 patch->mod->core_kallsyms.strtab,
842 info->symndx, i, obj->name, apply);
843 if (ret)
844 return ret;
845 }
846
847 return 0;
848}
849
850static int klp_apply_object_relocs(struct klp_patch *patch,
851 struct klp_object *obj)
852{
853 return klp_write_object_relocs(patch, obj, true);
854}
855
856static void klp_clear_object_relocs(struct klp_patch *patch,
857 struct klp_object *obj)
858{
859 klp_write_object_relocs(patch, obj, false);
860}
861
862/* parts of the initialization that is done only when the object is loaded */
863static int klp_init_object_loaded(struct klp_patch *patch,
864 struct klp_object *obj)
865{
866 struct klp_func *func;
867 int ret;
868
869 if (klp_is_module(obj)) {
870 /*
871 * Only write module-specific relocations here
872 * (.klp.rela.{module}.*). vmlinux-specific relocations were
873 * written earlier during the initialization of the klp module
874 * itself.
875 */
876 ret = klp_apply_object_relocs(patch, obj);
877 if (ret)
878 return ret;
879 }
880
881 klp_for_each_func(obj, func) {
882 ret = klp_find_object_symbol(obj->name, func->old_name,
883 func->old_sympos,
884 (unsigned long *)&func->old_func);
885 if (ret)
886 return ret;
887
888 ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
889 &func->old_size, NULL);
890 if (!ret) {
891 pr_err("kallsyms size lookup failed for '%s'\n",
892 func->old_name);
893 return -ENOENT;
894 }
895
896 if (func->nop)
897 func->new_func = func->old_func;
898
899 ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
900 &func->new_size, NULL);
901 if (!ret) {
902 pr_err("kallsyms size lookup failed for '%s' replacement\n",
903 func->old_name);
904 return -ENOENT;
905 }
906 }
907
908 return 0;
909}
910
911static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
912{
913 struct klp_func *func;
914 int ret;
915 const char *name;
916
917 if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
918 return -EINVAL;
919
920 obj->patched = false;
921 obj->mod = NULL;
922
923 klp_find_object_module(obj);
924
925 name = klp_is_module(obj) ? obj->name : "vmlinux";
926 ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
927 if (ret)
928 return ret;
929
930 klp_for_each_func(obj, func) {
931 ret = klp_init_func(obj, func);
932 if (ret)
933 return ret;
934 }
935
936 if (klp_is_object_loaded(obj))
937 ret = klp_init_object_loaded(patch, obj);
938
939 return ret;
940}
941
942static void klp_init_func_early(struct klp_object *obj,
943 struct klp_func *func)
944{
945 kobject_init(&func->kobj, &klp_ktype_func);
946 list_add_tail(&func->node, &obj->func_list);
947}
948
949static void klp_init_object_early(struct klp_patch *patch,
950 struct klp_object *obj)
951{
952 INIT_LIST_HEAD(&obj->func_list);
953 kobject_init(&obj->kobj, &klp_ktype_object);
954 list_add_tail(&obj->node, &patch->obj_list);
955}
956
957static void klp_init_patch_early(struct klp_patch *patch)
958{
959 struct klp_object *obj;
960 struct klp_func *func;
961
962 INIT_LIST_HEAD(&patch->list);
963 INIT_LIST_HEAD(&patch->obj_list);
964 kobject_init(&patch->kobj, &klp_ktype_patch);
965 patch->enabled = false;
966 patch->forced = false;
967 INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
968 init_completion(&patch->finish);
969
970 klp_for_each_object_static(patch, obj) {
971 klp_init_object_early(patch, obj);
972
973 klp_for_each_func_static(obj, func) {
974 klp_init_func_early(obj, func);
975 }
976 }
977}
978
979static int klp_init_patch(struct klp_patch *patch)
980{
981 struct klp_object *obj;
982 int ret;
983
984 ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
985 if (ret)
986 return ret;
987
988 if (patch->replace) {
989 ret = klp_add_nops(patch);
990 if (ret)
991 return ret;
992 }
993
994 klp_for_each_object(patch, obj) {
995 ret = klp_init_object(patch, obj);
996 if (ret)
997 return ret;
998 }
999
1000 list_add_tail(&patch->list, &klp_patches);
1001
1002 return 0;
1003}
1004
1005static int __klp_disable_patch(struct klp_patch *patch)
1006{
1007 struct klp_object *obj;
1008
1009 if (WARN_ON(!patch->enabled))
1010 return -EINVAL;
1011
1012 if (klp_transition_patch)
1013 return -EBUSY;
1014
1015 klp_init_transition(patch, KLP_TRANSITION_UNPATCHED);
1016
1017 klp_for_each_object(patch, obj)
1018 if (obj->patched)
1019 klp_pre_unpatch_callback(obj);
1020
1021 /*
1022 * Enforce the order of the func->transition writes in
1023 * klp_init_transition() and the TIF_PATCH_PENDING writes in
1024 * klp_start_transition(). In the rare case where klp_ftrace_handler()
1025 * is called shortly after klp_update_patch_state() switches the task,
1026 * this ensures the handler sees that func->transition is set.
1027 */
1028 smp_wmb();
1029
1030 klp_start_transition();
1031 patch->enabled = false;
1032 klp_try_complete_transition();
1033
1034 return 0;
1035}
1036
1037static int __klp_enable_patch(struct klp_patch *patch)
1038{
1039 struct klp_object *obj;
1040 int ret;
1041
1042 if (klp_transition_patch)
1043 return -EBUSY;
1044
1045 if (WARN_ON(patch->enabled))
1046 return -EINVAL;
1047
1048 pr_notice("enabling patch '%s'\n", patch->mod->name);
1049
1050 klp_init_transition(patch, KLP_TRANSITION_PATCHED);
1051
1052 /*
1053 * Enforce the order of the func->transition writes in
1054 * klp_init_transition() and the ops->func_stack writes in
1055 * klp_patch_object(), so that klp_ftrace_handler() will see the
1056 * func->transition updates before the handler is registered and the
1057 * new funcs become visible to the handler.
1058 */
1059 smp_wmb();
1060
1061 klp_for_each_object(patch, obj) {
1062 if (!klp_is_object_loaded(obj))
1063 continue;
1064
1065 ret = klp_pre_patch_callback(obj);
1066 if (ret) {
1067 pr_warn("pre-patch callback failed for object '%s'\n",
1068 klp_is_module(obj) ? obj->name : "vmlinux");
1069 goto err;
1070 }
1071
1072 ret = klp_patch_object(obj);
1073 if (ret) {
1074 pr_warn("failed to patch object '%s'\n",
1075 klp_is_module(obj) ? obj->name : "vmlinux");
1076 goto err;
1077 }
1078 }
1079
1080 klp_start_transition();
1081 patch->enabled = true;
1082 klp_try_complete_transition();
1083
1084 return 0;
1085err:
1086 pr_warn("failed to enable patch '%s'\n", patch->mod->name);
1087
1088 klp_cancel_transition();
1089 return ret;
1090}
1091
1092static int klp_check_patch(struct klp_patch *patch)
1093{
1094 struct klp_object *obj;
1095 struct klp_func *func;
1096
1097 if (!patch || !patch->mod || !patch->objs)
1098 return -EINVAL;
1099
1100 klp_for_each_object_static(patch, obj) {
1101 if (!obj->funcs)
1102 return -EINVAL;
1103 klp_for_each_func_static(obj, func) {
1104 if (!func->old_name)
1105 return -EINVAL;
1106 }
1107 }
1108 return 0;
1109}
1110
1111/**
1112 * klp_enable_patch() - enable the livepatch
1113 * @patch: patch to be enabled
1114 *
1115 * Initializes the data structure associated with the patch, creates the sysfs
1116 * interface, performs the needed symbol lookups and code relocations,
1117 * registers the patched functions with ftrace.
1118 *
1119 * This function is supposed to be called from the livepatch module_init()
1120 * callback.
1121 *
1122 * Return: 0 on success, otherwise error
1123 */
1124int klp_enable_patch(struct klp_patch *patch)
1125{
1126 int ret;
1127
1128 ret = klp_check_patch(patch);
1129 if (ret)
1130 return ret;
1131
1132 if (!is_livepatch_module(patch->mod)) {
1133 pr_err("module %s is not marked as a livepatch module\n",
1134 patch->mod->name);
1135 return -EINVAL;
1136 }
1137
1138 if (!klp_initialized())
1139 return -ENODEV;
1140
1141 if (!klp_have_reliable_stack()) {
1142 pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
1143 pr_warn("The livepatch transition may never complete.\n");
1144 }
1145
1146 mutex_lock(&klp_mutex);
1147
1148 if (!klp_is_patch_compatible(patch)) {
1149 pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
1150 patch->mod->name);
1151 mutex_unlock(&klp_mutex);
1152 return -EINVAL;
1153 }
1154
1155 if (!try_module_get(patch->mod)) {
1156 mutex_unlock(&klp_mutex);
1157 return -ENODEV;
1158 }
1159
1160 klp_init_patch_early(patch);
1161
1162 ret = klp_init_patch(patch);
1163 if (ret)
1164 goto err;
1165
1166 ret = __klp_enable_patch(patch);
1167 if (ret)
1168 goto err;
1169
1170 mutex_unlock(&klp_mutex);
1171
1172 return 0;
1173
1174err:
1175 klp_free_patch_start(patch);
1176
1177 mutex_unlock(&klp_mutex);
1178
1179 klp_free_patch_finish(patch);
1180
1181 return ret;
1182}
1183EXPORT_SYMBOL_GPL(klp_enable_patch);
1184
1185/*
1186 * This function unpatches objects from the replaced livepatches.
1187 *
1188 * We could be pretty aggressive here. It is called in the situation where
1189 * these structures are no longer accessed from the ftrace handler.
1190 * All functions are redirected by the klp_transition_patch. They
1191 * use either a new code or they are in the original code because
1192 * of the special nop function patches.
1193 *
1194 * The only exception is when the transition was forced. In this case,
1195 * klp_ftrace_handler() might still see the replaced patch on the stack.
1196 * Fortunately, it is carefully designed to work with removed functions
1197 * thanks to RCU. We only have to keep the patches on the system. Also
1198 * this is handled transparently by patch->module_put.
1199 */
1200void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
1201{
1202 struct klp_patch *old_patch;
1203
1204 klp_for_each_patch(old_patch) {
1205 if (old_patch == new_patch)
1206 return;
1207
1208 old_patch->enabled = false;
1209 klp_unpatch_objects(old_patch);
1210 }
1211}
1212
1213/*
1214 * This function removes the dynamically allocated 'nop' functions.
1215 *
1216 * We could be pretty aggressive. NOPs do not change the existing
1217 * behavior except for adding unnecessary delay by the ftrace handler.
1218 *
1219 * It is safe even when the transition was forced. The ftrace handler
1220 * will see a valid ops->func_stack entry thanks to RCU.
1221 *
1222 * We could even free the NOPs structures. They must be the last entry
1223 * in ops->func_stack. Therefore unregister_ftrace_function() is called.
1224 * It does the same as klp_synchronize_transition() to make sure that
1225 * nobody is inside the ftrace handler once the operation finishes.
1226 *
1227 * IMPORTANT: It must be called right after removing the replaced patches!
1228 */
1229void klp_discard_nops(struct klp_patch *new_patch)
1230{
1231 klp_unpatch_objects_dynamic(klp_transition_patch);
1232 klp_free_objects_dynamic(klp_transition_patch);
1233}
1234
1235/*
1236 * Remove parts of patches that touch a given kernel module. The list of
1237 * patches processed might be limited. When limit is NULL, all patches
1238 * will be handled.
1239 */
1240static void klp_cleanup_module_patches_limited(struct module *mod,
1241 struct klp_patch *limit)
1242{
1243 struct klp_patch *patch;
1244 struct klp_object *obj;
1245
1246 klp_for_each_patch(patch) {
1247 if (patch == limit)
1248 break;
1249
1250 klp_for_each_object(patch, obj) {
1251 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1252 continue;
1253
1254 if (patch != klp_transition_patch)
1255 klp_pre_unpatch_callback(obj);
1256
1257 pr_notice("reverting patch '%s' on unloading module '%s'\n",
1258 patch->mod->name, obj->mod->name);
1259 klp_unpatch_object(obj);
1260
1261 klp_post_unpatch_callback(obj);
1262 klp_clear_object_relocs(patch, obj);
1263 klp_free_object_loaded(obj);
1264 break;
1265 }
1266 }
1267}
1268
1269int klp_module_coming(struct module *mod)
1270{
1271 int ret;
1272 struct klp_patch *patch;
1273 struct klp_object *obj;
1274
1275 if (WARN_ON(mod->state != MODULE_STATE_COMING))
1276 return -EINVAL;
1277
1278 if (!strcmp(mod->name, "vmlinux")) {
1279 pr_err("vmlinux.ko: invalid module name\n");
1280 return -EINVAL;
1281 }
1282
1283 mutex_lock(&klp_mutex);
1284 /*
1285 * Each module has to know that klp_module_coming()
1286 * has been called. We never know what module will
1287 * get patched by a new patch.
1288 */
1289 mod->klp_alive = true;
1290
1291 klp_for_each_patch(patch) {
1292 klp_for_each_object(patch, obj) {
1293 if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
1294 continue;
1295
1296 obj->mod = mod;
1297
1298 ret = klp_init_object_loaded(patch, obj);
1299 if (ret) {
1300 pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
1301 patch->mod->name, obj->mod->name, ret);
1302 goto err;
1303 }
1304
1305 pr_notice("applying patch '%s' to loading module '%s'\n",
1306 patch->mod->name, obj->mod->name);
1307
1308 ret = klp_pre_patch_callback(obj);
1309 if (ret) {
1310 pr_warn("pre-patch callback failed for object '%s'\n",
1311 obj->name);
1312 goto err;
1313 }
1314
1315 ret = klp_patch_object(obj);
1316 if (ret) {
1317 pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
1318 patch->mod->name, obj->mod->name, ret);
1319
1320 klp_post_unpatch_callback(obj);
1321 goto err;
1322 }
1323
1324 if (patch != klp_transition_patch)
1325 klp_post_patch_callback(obj);
1326
1327 break;
1328 }
1329 }
1330
1331 mutex_unlock(&klp_mutex);
1332
1333 return 0;
1334
1335err:
1336 /*
1337 * If a patch is unsuccessfully applied, return
1338 * error to the module loader.
1339 */
1340 pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
1341 patch->mod->name, obj->mod->name, obj->mod->name);
1342 mod->klp_alive = false;
1343 obj->mod = NULL;
1344 klp_cleanup_module_patches_limited(mod, patch);
1345 mutex_unlock(&klp_mutex);
1346
1347 return ret;
1348}
1349
1350void klp_module_going(struct module *mod)
1351{
1352 if (WARN_ON(mod->state != MODULE_STATE_GOING &&
1353 mod->state != MODULE_STATE_COMING))
1354 return;
1355
1356 mutex_lock(&klp_mutex);
1357 /*
1358 * Each module has to know that klp_module_going()
1359 * has been called. We never know what module will
1360 * get patched by a new patch.
1361 */
1362 mod->klp_alive = false;
1363
1364 klp_cleanup_module_patches_limited(mod, NULL);
1365
1366 mutex_unlock(&klp_mutex);
1367}
1368
1369void *klp_find_section_by_name(const struct module *mod, const char *name,
1370 size_t *sec_size)
1371{
1372 struct klp_modinfo *info = mod->klp_info;
1373
1374 for (int i = 1; i < info->hdr.e_shnum; i++) {
1375 Elf_Shdr *shdr = &info->sechdrs[i];
1376
1377 if (!strcmp(info->secstrings + shdr->sh_name, name)) {
1378 *sec_size = shdr->sh_size;
1379 return (void *)shdr->sh_addr;
1380 }
1381 }
1382
1383 *sec_size = 0;
1384 return NULL;
1385}
1386EXPORT_SYMBOL_GPL(klp_find_section_by_name);
1387
1388static int __init klp_init(void)
1389{
1390 klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
1391 if (!klp_root_kobj)
1392 return -ENOMEM;
1393
1394 return 0;
1395}
1396
1397module_init(klp_init);