kernel/livepatch/core.c

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