1 /*
2 * Copyright (C) 2012 Oracle.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version 2
7 * of the License, or (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
16 */
17
18 /*
19 * The point here is to store that a buffer has x bytes even if we don't know
20 * the value of x.
21 *
22 */
23
24 #include "smatch.h"
25 #include "smatch_extra.h"
26 #include "smatch_slist.h"
27
28 static int size_id;
29 static int link_id;
30
31 /*
32 * We need this for code which does:
33 *
34 * if (size)
35 * foo = malloc(size);
36 *
37 * We want to record that the size of "foo" is "size" even after the merge.
38 *
39 */
40 static struct smatch_state *unmatched_state(struct sm_state *sm)
41 {
42 struct expression *size_expr;
43 sval_t sval;
44
45 if (!sm->state->data)
46 return &undefined;
47 size_expr = sm->state->data;
48 if (!get_implied_value(size_expr, &sval) || sval.value != 0)
49 return &undefined;
50 return sm->state;
51 }
52
53 static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
54 {
55 struct expression *expr1, *expr2;
56
57 expr1 = s1->data;
58 expr2 = s2->data;
59
60 if (expr1 && expr2 && expr_equiv(expr1, expr2))
61 return s1;
62 return &merged;
63 }
64
65 static void match_link_modify(struct sm_state *sm, struct expression *mod_expr)
66 {
67 struct expression *expr;
68 struct sm_state *tmp;
69
70 expr = sm->state->data;
71 if (expr) {
72 set_state_expr(size_id, expr, &undefined);
73 set_state(link_id, sm->name, sm->sym, &undefined);
74 return;
75 }
76
77 FOR_EACH_PTR(sm->possible, tmp) {
78 expr = tmp->state->data;
79 if (expr)
80 set_state_expr(size_id, expr, &undefined);
81 } END_FOR_EACH_PTR(tmp);
82 set_state(link_id, sm->name, sm->sym, &undefined);
83 }
84
85 static struct smatch_state *alloc_expr_state(struct expression *expr)
86 {
87 struct smatch_state *state;
88 char *name;
89
90 state = __alloc_smatch_state(0);
91 expr = strip_expr(expr);
92 name = expr_to_str(expr);
93 state->name = alloc_sname(name);
94 free_string(name);
95 state->data = expr;
96 return state;
97 }
98
99 static int bytes_per_element(struct expression *expr)
100 {
101 struct symbol *type;
102
103 type = get_type(expr);
104 if (!type)
105 return 0;
106
107 if (type->type != SYM_PTR && type->type != SYM_ARRAY)
108 return 0;
109
110 type = get_base_type(type);
111 return type_bytes(type);
112 }
113
114 static void db_save_type_links(struct expression *array, struct expression *size)
115 {
116 const char *array_name;
117
118 array_name = get_data_info_name(array);
119 if (!array_name)
120 array_name = "";
121 sql_insert_data_info(size, ARRAY_LEN, array_name);
122 }
123
124 static void match_alloc_helper(struct expression *pointer, struct expression *size)
125 {
126 struct expression *tmp;
127 struct sm_state *sm;
128 sval_t sval;
129 int cnt = 0;
130
131 pointer = strip_expr(pointer);
132 size = strip_expr(size);
133 if (!size || !pointer)
134 return;
135
136 while ((tmp = get_assigned_expr(size))) {
137 size = strip_expr(tmp);
138 if (cnt++ > 5)
139 break;
140 }
141
142 if (size->type == EXPR_BINOP && size->op == '*') {
143 struct expression *mult_left, *mult_right;
144
145 mult_left = strip_expr(size->left);
146 mult_right = strip_expr(size->right);
147
148 if (get_implied_value(mult_left, &sval) &&
149 sval.value == bytes_per_element(pointer))
150 size = mult_right;
151 else if (get_implied_value(mult_right, &sval) &&
152 sval.value == bytes_per_element(pointer))
153 size = mult_left;
154 else
155 return;
156 }
157
158 /* Only save links to variables, not fixed sizes */
159 if (get_value(size, &sval))
160 return;
161
162 db_save_type_links(pointer, size);
163 sm = set_state_expr(size_id, pointer, alloc_expr_state(size));
164 if (!sm)
165 return;
166 set_state_expr(link_id, size, alloc_expr_state(pointer));
167 }
168
169 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
170 {
171 int size_arg = PTR_INT(_size_arg);
172 struct expression *pointer, *call, *arg;
173
174 pointer = strip_expr(expr->left);
175 call = strip_expr(expr->right);
176 arg = get_argument_from_call_expr(call->args, size_arg);
177 match_alloc_helper(pointer, arg);
178 }
179
180 static void match_calloc(const char *fn, struct expression *expr, void *_start_arg)
181 {
182 int start_arg = PTR_INT(_start_arg);
183 struct expression *pointer, *call, *arg;
184 struct sm_state *tmp;
185 sval_t sval;
186
187 pointer = strip_expr(expr->left);
188 call = strip_expr(expr->right);
189 arg = get_argument_from_call_expr(call->args, start_arg);
190 if (get_implied_value(arg, &sval) &&
191 sval.value == bytes_per_element(pointer))
192 arg = get_argument_from_call_expr(call->args, start_arg + 1);
193
194 db_save_type_links(pointer, arg);
195 tmp = set_state_expr(size_id, pointer, alloc_expr_state(arg));
196 if (!tmp)
197 return;
198 set_state_expr(link_id, arg, alloc_expr_state(pointer));
199 }
200
201 struct expression *get_size_variable(struct expression *buf)
202 {
203 struct smatch_state *state;
204
205 state = get_state_expr(size_id, buf);
206 if (state)
207 return state->data;
208 return NULL;
209 }
210
211 struct expression *get_array_variable(struct expression *size)
212 {
213 struct smatch_state *state;
214
215 state = get_state_expr(link_id, size);
216 if (state)
217 return state->data;
218 return NULL;
219 }
220
221 static void array_check(struct expression *expr)
222 {
223 struct expression *array;
224 struct expression *size;
225 struct expression *offset;
226 char *array_str, *offset_str;
227
228 expr = strip_expr(expr);
229 if (!is_array(expr))
230 return;
231
232 array = get_array_base(expr);
233 size = get_size_variable(array);
234 if (!size)
235 return;
236 offset = get_array_offset(expr);
237 if (!possible_comparison(size, SPECIAL_EQUAL, offset))
238 return;
239
240 array_str = expr_to_str(array);
241 offset_str = expr_to_str(offset);
242 sm_warning("potentially one past the end of array '%s[%s]'", array_str, offset_str);
243 free_string(array_str);
244 free_string(offset_str);
245 }
246
247 struct db_info {
248 char *name;
249 int ret;
250 };
251
252 static int db_limitter_callback(void *_info, int argc, char **argv, char **azColName)
253 {
254 struct db_info *info = _info;
255
256 /*
257 * If possible the limitters are tied to the struct they limit. If we
258 * aren't sure which struct they limit then we use them as limitters for
259 * everything.
260 */
261 if (!info->name || argv[0][0] == '\0' || strcmp(info->name, argv[0]) == 0)
262 info->ret = 1;
263 return 0;
264 }
265
266 static char *vsl_to_data_info_name(const char *name, struct var_sym_list *vsl)
267 {
268 struct var_sym *vs;
269 struct symbol *type;
270 static char buf[80];
271 const char *p;
272
273 if (ptr_list_size((struct ptr_list *)vsl) != 1)
274 return NULL;
275 vs = first_ptr_list((struct ptr_list *)vsl);
276
277 type = get_real_base_type(vs->sym);
278 if (!type || type->type != SYM_PTR)
279 goto top_level_name;
280 type = get_real_base_type(type);
281 if (!type || type->type != SYM_STRUCT)
282 goto top_level_name;
283 if (!type->ident)
284 goto top_level_name;
285
286 p = name;
287 while ((name = strstr(p, "->")))
288 p = name + 2;
289
290 snprintf(buf, sizeof(buf),"(struct %s)->%s", type->ident->name, p);
291 return alloc_sname(buf);
292
293 top_level_name:
294 if (!(vs->sym->ctype.modifiers & MOD_TOPLEVEL))
295 return NULL;
296 if (vs->sym->ctype.modifiers & MOD_STATIC)
297 snprintf(buf, sizeof(buf),"static %s", name);
298 else
299 snprintf(buf, sizeof(buf),"global %s", name);
300 return alloc_sname(buf);
301 }
302
303 int db_var_is_array_limit(struct expression *array, const char *name, struct var_sym_list *vsl)
304 {
305 char *size_name;
306 char *array_name = get_data_info_name(array);
307 struct db_info db_info = {.name = array_name,};
308
309 size_name = vsl_to_data_info_name(name, vsl);
310 if (!size_name)
311 return 0;
312
313 run_sql(db_limitter_callback, &db_info,
314 "select value from data_info where type = %d and data = '%s';",
315 ARRAY_LEN, size_name);
316
317 return db_info.ret;
318 }
319
320 static int known_access_ok_comparison(struct expression *expr)
321 {
322 struct expression *array;
323 struct expression *size;
324 struct expression *offset;
325 int comparison;
326
327 array = get_array_base(expr);
328 size = get_size_variable(array);
329 if (!size)
330 return 0;
331 offset = get_array_offset(expr);
332 comparison = get_comparison(size, offset);
333 if (comparison == '>' || comparison == SPECIAL_UNSIGNED_GT)
334 return 1;
335
336 return 0;
337 }
338
339 static int known_access_ok_numbers(struct expression *expr)
340 {
341 struct expression *array;
342 struct expression *offset;
343 sval_t max;
344 int size;
345
346 array = get_array_base(expr);
347 offset = get_array_offset(expr);
348
349 size = get_array_size(array);
350 if (size <= 0)
351 return 0;
352
353 get_absolute_max(offset, &max);
354 if (max.uvalue < size)
355 return 1;
356 return 0;
357 }
358
359 static void array_check_data_info(struct expression *expr)
360 {
361 struct expression *array;
362 struct expression *offset;
363 struct state_list *slist;
364 struct sm_state *sm;
365 struct compare_data *comp;
366 char *offset_name;
367 const char *equal_name = NULL;
368
369 expr = strip_expr(expr);
370 if (!is_array(expr))
371 return;
372
373 if (known_access_ok_numbers(expr))
374 return;
375 if (known_access_ok_comparison(expr))
376 return;
377
378 array = get_array_base(expr);
379 offset = get_array_offset(expr);
380 offset_name = expr_to_var(offset);
381 if (!offset_name)
382 return;
383 slist = get_all_possible_equal_comparisons(offset);
384 if (!slist)
385 goto free;
386
387 FOR_EACH_PTR(slist, sm) {
388 comp = sm->state->data;
389 if (strcmp(comp->left_var, offset_name) == 0) {
390 if (db_var_is_array_limit(array, comp->right_var, comp->right_vsl)) {
391 equal_name = comp->right_var;
392 break;
393 }
394 } else if (strcmp(comp->right_var, offset_name) == 0) {
395 if (db_var_is_array_limit(array, comp->left_var, comp->left_vsl)) {
396 equal_name = comp->left_var;
397 break;
398 }
399 }
400 } END_FOR_EACH_PTR(sm);
401
402 if (equal_name) {
403 char *array_name = expr_to_str(array);
404
405 sm_warning("potential off by one '%s[]' limit '%s'", array_name, equal_name);
406 free_string(array_name);
407 }
408
409 free:
410 free_slist(&slist);
411 free_string(offset_name);
412 }
413
414 static void add_allocation_function(const char *func, void *call_back, int param)
415 {
416 add_function_assign_hook(func, call_back, INT_PTR(param));
417 }
418
419 static char *buf_size_param_comparison(struct expression *array, struct expression_list *args)
420 {
421 struct expression *arg;
422 struct expression *size;
423 static char buf[32];
424 int i;
425
426 size = get_size_variable(array);
427 if (!size)
428 return NULL;
429
430 i = -1;
431 FOR_EACH_PTR(args, arg) {
432 i++;
433 if (arg == array)
434 continue;
435 if (!expr_equiv(arg, size))
436 continue;
437 snprintf(buf, sizeof(buf), "==$%d", i);
438 return buf;
439 } END_FOR_EACH_PTR(arg);
440
441 return NULL;
442 }
443
444 static void match_call(struct expression *call)
445 {
446 struct expression *arg;
447 char *compare;
448 int param;
449
450 param = -1;
451 FOR_EACH_PTR(call->args, arg) {
452 param++;
453 if (!is_pointer(arg))
454 continue;
455 compare = buf_size_param_comparison(arg, call->args);
456 if (!compare)
457 continue;
458 sql_insert_caller_info(call, ARRAY_LEN, param, "$", compare);
459 } END_FOR_EACH_PTR(arg);
460 }
461
462 static int get_param(int param, char **name, struct symbol **sym)
463 {
464 struct symbol *arg;
465 int i;
466
467 i = 0;
468 FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, arg) {
469 /*
470 * this is a temporary hack to work around a bug (I think in sparse?)
471 * 2.6.37-rc1:fs/reiserfs/journal.o
472 * If there is a function definition without parameter name found
473 * after a function implementation then it causes a crash.
474 * int foo() {}
475 * int bar(char *);
476 */
477 if (arg->ident->name < (char *)100)
478 continue;
479 if (i == param) {
480 *name = arg->ident->name;
481 *sym = arg;
482 return TRUE;
483 }
484 i++;
485 } END_FOR_EACH_PTR(arg);
486
487 return FALSE;
488 }
489
490 static void set_param_compare(const char *array_name, struct symbol *array_sym, char *key, char *value)
491 {
492 struct expression *array_expr;
493 struct expression *size_expr;
494 struct symbol *size_sym;
495 char *size_name;
496 long param;
497 struct sm_state *tmp;
498
499 if (strncmp(value, "==$", 3) != 0)
500 return;
501 param = strtol(value + 3, NULL, 10);
502 if (!get_param(param, &size_name, &size_sym))
503 return;
504 array_expr = symbol_expression(array_sym);
505 size_expr = symbol_expression(size_sym);
506
507 tmp = set_state_expr(size_id, array_expr, alloc_expr_state(size_expr));
508 if (!tmp)
509 return;
510 set_state_expr(link_id, size_expr, alloc_expr_state(array_expr));
511 }
512
513 static void set_arraysize_arg(const char *array_name, struct symbol *array_sym, char *key, char *value)
514 {
515 struct expression *array_expr;
516 struct expression *size_expr;
517 struct symbol *size_sym;
518 char *size_name;
519 long param;
520 struct sm_state *tmp;
521
522 param = strtol(key, NULL, 10);
523 if (!get_param(param, &size_name, &size_sym))
524 return;
525 array_expr = symbol_expression(array_sym);
526 size_expr = symbol_expression(size_sym);
527
528 tmp = set_state_expr(size_id, array_expr, alloc_expr_state(size_expr));
529 if (!tmp)
530 return;
531 set_state_expr(link_id, size_expr, alloc_expr_state(array_expr));
532 }
533
534 static void munge_start_states(struct statement *stmt)
535 {
536 struct state_list *slist = NULL;
537 struct sm_state *sm;
538 struct sm_state *poss;
539
540 FOR_EACH_MY_SM(size_id, __get_cur_stree(), sm) {
541 if (sm->state != &merged)
542 continue;
543 /*
544 * screw it. let's just assume that if one caller passes the
545 * size then they all do.
546 */
547 FOR_EACH_PTR(sm->possible, poss) {
548 if (poss->state != &merged &&
549 poss->state != &undefined) {
550 add_ptr_list(&slist, poss);
551 break;
552 }
553 } END_FOR_EACH_PTR(poss);
554 } END_FOR_EACH_SM(sm);
555
556 FOR_EACH_PTR(slist, sm) {
557 set_state(size_id, sm->name, sm->sym, sm->state);
558 } END_FOR_EACH_PTR(sm);
559
560 free_slist(&slist);
561 }
562
563 void register_buf_comparison(int id)
564 {
565 size_id = id;
566
567 add_unmatched_state_hook(size_id, &unmatched_state);
568
569 add_allocation_function("malloc", &match_alloc, 0);
570 add_allocation_function("memdup", &match_alloc, 1);
571 add_allocation_function("realloc", &match_alloc, 1);
572 if (option_project == PROJ_KERNEL) {
573 add_allocation_function("kmalloc", &match_alloc, 0);
574 add_allocation_function("kzalloc", &match_alloc, 0);
575 add_allocation_function("vmalloc", &match_alloc, 0);
576 add_allocation_function("__vmalloc", &match_alloc, 0);
577 add_allocation_function("sock_kmalloc", &match_alloc, 1);
578 add_allocation_function("kmemdup", &match_alloc, 1);
579 add_allocation_function("kmemdup_user", &match_alloc, 1);
580 add_allocation_function("dma_alloc_attrs", &match_alloc, 1);
581 add_allocation_function("pci_alloc_consistent", &match_alloc, 1);
582 add_allocation_function("pci_alloc_coherent", &match_alloc, 1);
583 add_allocation_function("devm_kmalloc", &match_alloc, 1);
584 add_allocation_function("devm_kzalloc", &match_alloc, 1);
585 add_allocation_function("kcalloc", &match_calloc, 0);
586 add_allocation_function("devm_kcalloc", &match_calloc, 1);
587 add_allocation_function("kmalloc_array", &match_calloc, 0);
588 add_allocation_function("krealloc", &match_alloc, 1);
589 }
590
591 add_hook(&array_check, OP_HOOK);
592 add_hook(&array_check_data_info, OP_HOOK);
593
594 add_hook(&match_call, FUNCTION_CALL_HOOK);
595 select_caller_info_hook(set_param_compare, ARRAY_LEN);
596 select_caller_info_hook(set_arraysize_arg, ARRAYSIZE_ARG);
597 add_hook(&munge_start_states, AFTER_DEF_HOOK);
598 }
599
600 void register_buf_comparison_links(int id)
601 {
602 link_id = id;
603 add_merge_hook(link_id, &merge_links);
604 add_modification_hook(link_id, &match_link_modify);
605 }