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dereference: handle frob(&foo->bar); better
[smatch.git] / smatch_kernel_user_data.c
blob9434103c6758ca521e8ba550649527eaaf4098a5
1 /*
2 * Copyright (C) 2011 Dan Carpenter.
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 * There are a couple checks that try to see if a variable
20 * comes from the user. It would be better to unify them
21 * into one place. Also it we should follow the data down
22 * the call paths. Hence this file.
23 */
24
25 #include "smatch.h"
26 #include "smatch_slist.h"
27 #include "smatch_extra.h"
28
29 static int my_id;
30 static int my_call_id;
31
32 static struct expression *ignore_clear;
33
34 STATE(called);
35 static unsigned long func_gets_user_data;
36
37 struct user_fn_info {
38 const char *name;
39 int type;
40 int param;
41 const char *key;
42 const sval_t *implies_start, *implies_end;
43 func_hook *call_back;
44 };
45
46 static struct user_fn_info func_table[] = {
47 { "iov_iter_count", USER_DATA, -1, "$" },
48 { "simple_strtol", USER_DATA, -1, "$" },
49 { "simple_strtoll", USER_DATA, -1, "$" },
50 { "simple_strtoul", USER_DATA, -1, "$" },
51 { "simple_strtoull", USER_DATA, -1, "$" },
52 { "kvm_register_read", USER_DATA, -1, "$" },
53 };
54
55 static struct smatch_state *empty_state(struct sm_state *sm)
56 {
57 return alloc_estate_empty();
58 }
59
60 static struct smatch_state *new_state(struct symbol *type)
61 {
62 struct smatch_state *state;
63
64 if (!type || type_is_ptr(type))
65 return NULL;
66
67 state = alloc_estate_whole(type);
68 estate_set_new(state);
69 return state;
70 }
71
72 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
73 {
74 struct smatch_state *user = cur->state;
75 struct smatch_state *extra;
76 struct smatch_state *state;
77 struct range_list *rl;
78
79 extra = __get_state(SMATCH_EXTRA, cur->name, cur->sym);
80 if (!extra)
81 return;
82 rl = rl_intersection(estate_rl(user), estate_rl(extra));
83 state = alloc_estate_rl(clone_rl(rl));
84 if (estate_capped(user) || is_capped_var_sym(cur->name, cur->sym))
85 estate_set_capped(state);
86 if (estate_treat_untagged(user))
87 estate_set_treat_untagged(state);
88 if (estates_equiv(state, cur->state))
89 return;
90 if (estate_new(cur->state))
91 estate_set_new(state);
92 set_state(my_id, cur->name, cur->sym, state);
93 }
94
95 static void extra_nomod_hook(const char *name, struct symbol *sym, struct expression *expr, struct smatch_state *state)
96 {
97 struct smatch_state *user, *new;
98 struct range_list *rl;
99
100 user = __get_state(my_id, name, sym);
101 if (!user)
102 return;
103 rl = rl_intersection(estate_rl(user), estate_rl(state));
104 if (rl_equiv(rl, estate_rl(user)))
105 return;
106 new = alloc_estate_rl(rl);
107 if (estate_capped(user))
108 estate_set_capped(new);
109 if (estate_treat_untagged(user))
110 estate_set_treat_untagged(new);
111 set_state(my_id, name, sym, new);
112 }
113
114 static void store_type_info(struct expression *expr, struct smatch_state *state)
115 {
116 struct symbol *type;
117 char *type_str, *member;
118
119 if (__in_fake_assign)
120 return;
121
122 if (!estate_rl(state))
123 return;
124
125 expr = strip_expr(expr);
126 if (!expr || expr->type != EXPR_DEREF || !expr->member)
127 return;
128
129 type = get_type(expr->deref);
130 if (!type || !type->ident)
131 return;
132
133 type_str = type_to_str(type);
134 if (!type_str)
135 return;
136 member = get_member_name(expr);
137 if (!member)
138 return;
139
140 sql_insert_function_type_info(USER_DATA, type_str, member, state->name);
141 }
142
143 static void set_user_data(struct expression *expr, struct smatch_state *state)
144 {
145 store_type_info(expr, state);
146 set_state_expr(my_id, expr, state);
147 }
148
149 static bool user_rl_known(struct expression *expr)
150 {
151 struct range_list *rl;
152 sval_t close_to_max;
153
154 if (!get_user_rl(expr, &rl))
155 return true;
156
157 close_to_max = sval_type_max(rl_type(rl));
158 close_to_max.value -= 100;
159
160 if (sval_cmp(rl_max(rl), close_to_max) >= 0)
161 return false;
162 return true;
163 }
164
165 static bool is_array_index_mask_nospec(struct expression *expr)
166 {
167 struct expression *orig;
168
169 orig = get_assigned_expr(expr);
170 if (!orig || orig->type != EXPR_CALL)
171 return false;
172 return sym_name_is("array_index_mask_nospec", orig->fn);
173 }
174
175 static bool binop_capped(struct expression *expr)
176 {
177 struct range_list *left_rl;
178 int comparison;
179 sval_t sval;
180
181 if (expr->op == '-' && get_user_rl(expr->left, &left_rl)) {
182 if (user_rl_capped(expr->left))
183 return true;
184 comparison = get_comparison(expr->left, expr->right);
185 if (comparison && show_special(comparison)[0] == '>')
186 return true;
187 return false;
188 }
189
190 if (expr->op == '&' || expr->op == '%') {
191 bool left_user, left_capped, right_user, right_capped;
192
193 if (!get_value(expr->right, &sval) && is_capped(expr->right))
194 return true;
195 if (is_array_index_mask_nospec(expr->right))
196 return true;
197 if (is_capped(expr->left))
198 return true;
199 left_user = is_user_rl(expr->left);
200 right_user = is_user_rl(expr->right);
201 if (!left_user && !right_user)
202 return true;
203
204 left_capped = user_rl_capped(expr->left);
205 right_capped = user_rl_capped(expr->right);
206
207 if (left_user && left_capped) {
208 if (!right_user)
209 return true;
210 if (right_user && right_capped)
211 return true;
212 return false;
213 }
214 if (right_user && right_capped) {
215 if (!left_user)
216 return true;
217 return false;
218 }
219 return false;
220 }
221
222 /*
223 * Generally "capped" means that we capped it to an unknown value.
224 * This is useful because if Smatch doesn't know what the value is then
225 * we have to trust that it is correct. But if we known cap value is
226 * 100 then we can check if 100 is correct and complain if it's wrong.
227 *
228 * So then the problem is with BINOP when we take a capped variable
229 * plus a user variable which is clamped to a known range (uncapped)
230 * the result should be capped.
231 */
232 if ((user_rl_capped(expr->left) || user_rl_known(expr->left)) &&
233 (user_rl_capped(expr->right) || user_rl_known(expr->right)))
234 return true;
235
236 return false;
237 }
238
239 bool user_rl_capped_var_sym(const char *name, struct symbol *sym)
240 {
241 struct smatch_state *state;
242
243 state = get_state(my_id, name, sym);
244 if (state)
245 return estate_capped(state);
246
247 return true;
248 }
249
250 bool user_rl_capped(struct expression *expr)
251 {
252 struct smatch_state *state;
253 struct range_list *rl;
254 sval_t sval;
255
256 expr = strip_expr(expr);
257 if (!expr)
258 return false;
259 if (get_value(expr, &sval))
260 return true;
261 if (expr->type == EXPR_BINOP)
262 return binop_capped(expr);
263 if ((expr->type == EXPR_PREOP || expr->type == EXPR_POSTOP) &&
264 (expr->op == SPECIAL_INCREMENT || expr->op == SPECIAL_DECREMENT))
265 return user_rl_capped(expr->unop);
266 state = get_state_expr(my_id, expr);
267 if (state)
268 return estate_capped(state);
269
270 if (!get_user_rl(expr, &rl)) {
271 /*
272 * The non user data parts of a binop are capped and
273 * also empty user rl states are capped.
274 */
275 return true;
276 }
277
278 if (rl_to_sval(rl, &sval))
279 return true;
280
281 return false; /* uncapped user data */
282 }
283
284 bool user_rl_treat_untagged(struct expression *expr)
285 {
286 struct smatch_state *state;
287 struct range_list *rl;
288 sval_t sval;
289
290 expr = strip_expr(expr);
291 if (!expr)
292 return false;
293 if (get_value(expr, &sval))
294 return true;
295
296 state = get_state_expr(my_id, expr);
297 if (state)
298 return estate_treat_untagged(state);
299
300 if (get_user_rl(expr, &rl))
301 return false; /* uncapped user data */
302
303 return true; /* not actually user data */
304 }
305
306 static int is_dev_attr_name(struct expression *expr)
307 {
308 char *name;
309 int ret = 0;
310
311 name = expr_to_str(expr);
312 if (!name)
313 return 0;
314 if (strstr(name, "->attr.name"))
315 ret = 1;
316 free_string(name);
317 return ret;
318 }
319
320 static bool is_percent_n(struct expression *expr, int pos)
321 {
322 char *p;
323 int cnt = 0;
324
325 if (!expr)
326 return false;
327 if (expr->type != EXPR_STRING || !expr->string)
328 return false;
329
330 p = expr->string->data;
331 while (*p) {
332 if (p[0] != '%' ||
333 (p[0] == '%' && p[1] == '%')) {
334 p++;
335 continue;
336 }
337 if (pos != cnt) {
338 cnt++;
339 p++;
340 continue;
341 }
342 if (p[1] == 'n')
343 return true;
344 return false;
345 }
346
347 return false;
348 }
349
350 static void match_sscanf(const char *fn, struct expression *expr, void *unused)
351 {
352 struct expression *str, *format, *arg;
353 int i;
354
355 func_gets_user_data = true;
356
357 str = get_argument_from_call_expr(expr->args, 0);
358 if (is_dev_attr_name(str))
359 return;
360
361 format = get_argument_from_call_expr(expr->args, 1);
362 if (is_dev_attr_name(format))
363 return;
364
365 i = -1;
366 FOR_EACH_PTR(expr->args, arg) {
367 i++;
368 if (i < 2)
369 continue;
370 if (is_percent_n(format, i - 2))
371 continue;
372 mark_as_user_data(deref_expression(arg), true);
373 } END_FOR_EACH_PTR(arg);
374 }
375
376 static int comes_from_skb_data(struct expression *expr)
377 {
378 expr = strip_expr(expr);
379 if (!expr || expr->type != EXPR_PREOP || expr->op != '*')
380 return 0;
381
382 expr = strip_expr(expr->unop);
383 if (!expr)
384 return 0;
385 if (expr->type == EXPR_BINOP && expr->op == '+')
386 expr = strip_expr(expr->left);
387
388 return is_skb_data(expr);
389 }
390
391 static int handle_get_user(struct expression *expr)
392 {
393 char *name;
394 int ret = 0;
395
396 name = get_macro_name(expr->pos);
397 if (!name || strcmp(name, "get_user") != 0)
398 return 0;
399
400 name = expr_to_var(expr->right);
401 if (!name || (strcmp(name, "__val_gu") != 0 && strcmp(name, "__gu_val") != 0))
402 goto free;
403 set_user_data(expr->left, new_state(get_type(expr->left)));
404 ret = 1;
405 free:
406 free_string(name);
407 return ret;
408 }
409
410 static bool state_is_new(struct expression *expr)
411 {
412 struct smatch_state *state;
413
414 state = get_state_expr(my_id, expr);
415 if (estate_new(state))
416 return true;
417
418 if (expr->type == EXPR_BINOP) {
419 if (state_is_new(expr->left))
420 return true;
421 if (state_is_new(expr->right))
422 return true;
423 }
424 return false;
425 }
426
427 static struct range_list *strip_negatives(struct range_list *rl)
428 {
429 sval_t min = rl_min(rl);
430 sval_t minus_one = { .type = rl_type(rl), .value = -1 };
431 sval_t over = { .type = rl_type(rl), .value = INT_MAX + 1ULL };
432 sval_t max = sval_type_max(rl_type(rl));
433
434 if (!rl)
435 return NULL;
436
437 if (type_unsigned(rl_type(rl)) && type_bits(rl_type(rl)) > 31)
438 return remove_range(rl, over, max);
439
440 return remove_range(rl, min, minus_one);
441 }
442
443 static bool handle_op_assign(struct expression *expr)
444 {
445 struct expression *binop_expr;
446 struct smatch_state *state;
447 struct range_list *rl;
448
449 switch (expr->op) {
450 case SPECIAL_ADD_ASSIGN:
451 case SPECIAL_SUB_ASSIGN:
452 case SPECIAL_AND_ASSIGN:
453 case SPECIAL_MOD_ASSIGN:
454 case SPECIAL_SHL_ASSIGN:
455 case SPECIAL_SHR_ASSIGN:
456 case SPECIAL_OR_ASSIGN:
457 case SPECIAL_XOR_ASSIGN:
458 case SPECIAL_MUL_ASSIGN:
459 case SPECIAL_DIV_ASSIGN:
460 binop_expr = binop_expression(expr->left,
461 op_remove_assign(expr->op),
462 expr->right);
463 if (!get_user_rl(binop_expr, &rl))
464 return true;
465
466 rl = cast_rl(get_type(expr->left), rl);
467 state = alloc_estate_rl(rl);
468 if (expr->op == SPECIAL_AND_ASSIGN ||
469 expr->op == SPECIAL_MOD_ASSIGN ||
470 user_rl_capped(binop_expr))
471 estate_set_capped(state);
472 if (user_rl_treat_untagged(expr->left))
473 estate_set_treat_untagged(state);
474 if (state_is_new(binop_expr))
475 estate_set_new(state);
476 estate_set_assigned(state);
477 set_user_data(expr->left, state);
478 return true;
479 }
480 return false;
481 }
482
483 static void handle_derefed_pointers(struct expression *expr, bool is_new)
484 {
485 expr = strip_expr(expr);
486 if (expr->type != EXPR_PREOP ||
487 expr->op != '*')
488 return;
489 expr = strip_expr(expr->unop);
490 set_array_user_ptr(expr, is_new);
491 }
492
493 static void match_assign(struct expression *expr)
494 {
495 struct symbol *left_type, *right_type;
496 struct range_list *rl = NULL;
497 static struct expression *handled;
498 struct smatch_state *state;
499 struct expression *faked;
500 bool is_capped = false;
501 bool is_new = false;
502
503 left_type = get_type(expr->left);
504 if (left_type == &void_ctype)
505 return;
506
507 faked = get_faked_expression();
508 if (faked && faked == ignore_clear)
509 return;
510
511 /* FIXME: handle fake array assignments frob(&user_array[x]); */
512
513 if (faked &&
514 faked->type == EXPR_ASSIGNMENT &&
515 points_to_user_data(faked->right)) {
516 if (is_skb_data(faked->right)) {
517 func_gets_user_data = true;
518 is_new = true;
519 }
520 rl = alloc_whole_rl(left_type);
521 goto set;
522 }
523
524 if (faked && faked == handled)
525 return;
526 if (is_fake_call(expr->right))
527 goto clear_old_state;
528 if (handle_get_user(expr))
529 return;
530 if (points_to_user_data(expr->right) &&
531 is_struct_ptr(get_type(expr->left))) {
532 handled = expr;
533 // This should be handled by smatch_points_to_user_data.c
534 // set_array_user_ptr(expr->left);
535 }
536
537 if (handle_op_assign(expr))
538 return;
539 if (expr->op != '=')
540 goto clear_old_state;
541
542 /* Handled by DB code */
543 if (expr->right->type == EXPR_CALL)
544 return;
545
546 if (faked)
547 disable_type_val_lookups();
548 get_user_rl(expr->right, &rl);
549 if (faked)
550 enable_type_val_lookups();
551 if (!rl)
552 goto clear_old_state;
553
554 is_capped = user_rl_capped(expr->right);
555 is_new = state_is_new(expr->right);
556
557 set:
558 right_type = get_type(expr->right);
559 if (type_is_ptr(left_type)) {
560 if (right_type && right_type->type == SYM_ARRAY)
561 set_array_user_ptr(expr->left, is_new);
562 return;
563 }
564
565 rl = cast_rl(left_type, rl);
566 if (is_capped && type_unsigned(right_type) && type_signed(left_type))
567 rl = strip_negatives(rl);
568 state = alloc_estate_rl(rl);
569 if (is_new)
570 estate_set_new(state);
571 if (is_capped)
572 estate_set_capped(state);
573 if (user_rl_treat_untagged(expr->right))
574 estate_set_treat_untagged(state);
575 estate_set_assigned(state);
576
577 set_user_data(expr->left, state);
578 handle_derefed_pointers(expr->left, is_new);
579 return;
580
581 clear_old_state:
582
583 /*
584 * HACK ALERT!!! This should be at the start of the function. The
585 * the problem is that handling "pointer = array;" assignments is
586 * handled in this function instead of in kernel_points_to_user_data.c.
587 */
588 if (type_is_ptr(left_type))
589 return;
590
591 if (get_state_expr(my_id, expr->left))
592 set_user_data(expr->left, alloc_estate_empty());
593 }
594
595 static void handle_eq_noteq(struct expression *expr)
596 {
597 struct smatch_state *left_orig, *right_orig;
598
599 left_orig = get_state_expr(my_id, expr->left);
600 right_orig = get_state_expr(my_id, expr->right);
601
602 if (!left_orig && !right_orig)
603 return;
604 if (left_orig && right_orig)
605 return;
606
607 if (left_orig) {
608 set_true_false_states_expr(my_id, expr->left,
609 expr->op == SPECIAL_EQUAL ? alloc_estate_empty() : NULL,
610 expr->op == SPECIAL_EQUAL ? NULL : alloc_estate_empty());
611 } else {
612 set_true_false_states_expr(my_id, expr->right,
613 expr->op == SPECIAL_EQUAL ? alloc_estate_empty() : NULL,
614 expr->op == SPECIAL_EQUAL ? NULL : alloc_estate_empty());
615 }
616 }
617
618 static void handle_compare(struct expression *expr)
619 {
620 struct expression *left, *right;
621 struct range_list *left_rl = NULL;
622 struct range_list *right_rl = NULL;
623 struct range_list *user_rl;
624 struct smatch_state *capped_state;
625 struct smatch_state *left_true = NULL;
626 struct smatch_state *left_false = NULL;
627 struct smatch_state *right_true = NULL;
628 struct smatch_state *right_false = NULL;
629 struct symbol *type;
630 sval_t sval;
631
632 left = strip_expr(expr->left);
633 right = strip_expr(expr->right);
634
635 while (left->type == EXPR_ASSIGNMENT)
636 left = strip_expr(left->left);
637
638 /*
639 * Conditions are mostly handled by smatch_extra.c, but there are some
640 * times where the exact values are not known so we can't do that.
641 *
642 * Normally, we might consider using smatch_capped.c to supliment smatch
643 * extra but that doesn't work when we merge unknown uncapped kernel
644 * data with unknown capped user data. The result is uncapped user
645 * data. We need to keep it separate and say that the user data is
646 * capped. In the past, I would have marked this as just regular
647 * kernel data (not user data) but we can't do that these days because
648 * we need to track user data for Spectre.
649 *
650 * The other situation which we have to handle is when we do have an
651 * int and we compare against an unknown unsigned kernel variable. In
652 * that situation we assume that the kernel data is less than INT_MAX.
653 * Otherwise then we get all sorts of array underflow false positives.
654 *
655 */
656
657 /* Handled in smatch_extra.c */
658 if (get_implied_value(left, &sval) ||
659 get_implied_value(right, &sval))
660 return;
661
662 get_user_rl(left, &left_rl);
663 get_user_rl(right, &right_rl);
664
665 /* nothing to do */
666 if (!left_rl && !right_rl)
667 return;
668 /* if both sides are user data that's not a good limit */
669 if (left_rl && right_rl)
670 return;
671
672 if (left_rl)
673 user_rl = left_rl;
674 else
675 user_rl = right_rl;
676
677 type = get_type(expr);
678 if (type_unsigned(type))
679 user_rl = strip_negatives(user_rl);
680 capped_state = alloc_estate_rl(user_rl);
681 estate_set_capped(capped_state);
682
683 switch (expr->op) {
684 case '<':
685 case SPECIAL_UNSIGNED_LT:
686 case SPECIAL_LTE:
687 case SPECIAL_UNSIGNED_LTE:
688 if (left_rl)
689 left_true = capped_state;
690 else
691 right_false = capped_state;
692 break;
693 case '>':
694 case SPECIAL_UNSIGNED_GT:
695 case SPECIAL_GTE:
696 case SPECIAL_UNSIGNED_GTE:
697 if (left_rl)
698 left_false = capped_state;
699 else
700 right_true = capped_state;
701 break;
702 }
703
704 set_true_false_states_expr(my_id, left, left_true, left_false);
705 set_true_false_states_expr(my_id, right, right_true, right_false);
706 }
707
708 static void match_condition(struct expression *expr)
709 {
710 if (expr->type != EXPR_COMPARE)
711 return;
712
713 if (expr->op == SPECIAL_EQUAL ||
714 expr->op == SPECIAL_NOTEQUAL) {
715 handle_eq_noteq(expr);
716 return;
717 }
718
719 handle_compare(expr);
720 }
721
722 static int get_user_macro_rl(struct expression *expr, struct range_list **rl)
723 {
724 struct expression *parent;
725 char *macro;
726
727 if (!expr)
728 return 0;
729
730 macro = get_macro_name(expr->pos);
731 if (!macro)
732 return 0;
733
734 /* handle ntohl(foo[i]) where "i" is trusted */
735 parent = expr_get_parent_expr(expr);
736 while (parent && parent->type != EXPR_BINOP)
737 parent = expr_get_parent_expr(parent);
738 if (parent && parent->type == EXPR_BINOP) {
739 char *parent_macro = get_macro_name(parent->pos);
740
741 if (parent_macro && strcmp(macro, parent_macro) == 0)
742 return 0;
743 }
744
745 if (strcmp(macro, "ntohl") == 0) {
746 *rl = alloc_whole_rl(&uint_ctype);
747 return 1;
748 }
749 if (strcmp(macro, "ntohs") == 0) {
750 *rl = alloc_whole_rl(&ushort_ctype);
751 return 1;
752 }
753 return 0;
754 }
755
756 static int has_user_data(struct symbol *sym)
757 {
758 struct sm_state *tmp;
759
760 FOR_EACH_MY_SM(my_id, __get_cur_stree(), tmp) {
761 if (tmp->sym == sym)
762 return 1;
763 } END_FOR_EACH_SM(tmp);
764 return 0;
765 }
766
767 bool we_pass_user_data(struct expression *call)
768 {
769 struct expression *arg;
770 struct symbol *sym;
771
772 FOR_EACH_PTR(call->args, arg) {
773 if (points_to_user_data(arg))
774 return true;
775 sym = expr_to_sym(arg);
776 if (!sym)
777 continue;
778 if (has_user_data(sym))
779 return true;
780 } END_FOR_EACH_PTR(arg);
781
782 return false;
783 }
784
785 // TODO: faked_assign this should already be handled
786 static int db_returned_user_rl(struct expression *call, struct range_list **rl)
787 {
788 struct smatch_state *state;
789 char buf[48];
790
791 if (is_fake_call(call))
792 return 0;
793 snprintf(buf, sizeof(buf), "return %p", call);
794 state = get_state(my_id, buf, NULL);
795 if (!state || !estate_rl(state))
796 return 0;
797 *rl = estate_rl(state);
798 return 1;
799 }
800
801 struct stree *get_user_stree(void)
802 {
803 return get_all_states_stree(my_id);
804 }
805
806 static struct int_stack *user_data_flags, *no_user_data_flags;
807
808 static void set_flag(struct int_stack **stack)
809 {
810 int num;
811
812 num = pop_int(stack);
813 num = 1;
814 push_int(stack, num);
815 }
816
817 struct range_list *var_user_rl(struct expression *expr)
818 {
819 struct smatch_state *state;
820 struct range_list *rl;
821 struct range_list *absolute_rl;
822
823 if (expr->type == EXPR_PREOP && expr->op == '&') {
824 set_flag(&no_user_data_flags);
825 return NULL;
826 }
827
828 if (expr->type == EXPR_BINOP && expr->op == '%') {
829 struct range_list *left, *right;
830
831 if (!get_user_rl(expr->right, &right))
832 return NULL;
833 get_absolute_rl(expr->left, &left);
834 rl = rl_binop(left, '%', right);
835 goto found;
836 }
837
838 if (expr->type == EXPR_BINOP && expr->op == '/') {
839 struct range_list *left = NULL;
840 struct range_list *right = NULL;
841 struct range_list *abs_right;
842
843 /*
844 * The specific bug I'm dealing with is:
845 *
846 * foo = capped_user / unknown;
847 *
848 * Instead of just saying foo is now entirely user_rl we should
849 * probably say instead that it is not at all user data.
850 *
851 */
852
853 get_user_rl(expr->left, &left);
854 get_user_rl(expr->right, &right);
855 get_absolute_rl(expr->right, &abs_right);
856
857 if (left && !right) {
858 rl = rl_binop(left, '/', abs_right);
859 if (sval_cmp(rl_max(left), rl_max(rl)) < 0)
860 set_flag(&no_user_data_flags);
861 }
862
863 return NULL;
864 }
865
866 if (get_user_macro_rl(expr, &rl))
867 goto found;
868
869 if (comes_from_skb_data(expr)) {
870 rl = alloc_whole_rl(get_type(expr));
871 goto found;
872 }
873
874 state = get_state_expr(my_id, expr);
875 if (state && estate_rl(state)) {
876 rl = estate_rl(state);
877 goto found;
878 }
879
880 if (expr->type == EXPR_CALL && db_returned_user_rl(expr, &rl))
881 goto found;
882
883 if (expr->type == EXPR_PREOP && expr->op == '*' &&
884 points_to_user_data(expr->unop)) {
885 rl = var_to_absolute_rl(expr);
886 goto found;
887 }
888
889 if (is_array(expr)) {
890 struct expression *array = get_array_base(expr);
891
892 if (!get_state_expr(my_id, array)) {
893 set_flag(&no_user_data_flags);
894 return NULL;
895 }
896 }
897
898 return NULL;
899 found:
900 set_flag(&user_data_flags);
901 absolute_rl = var_to_absolute_rl(expr);
902 return rl_intersection(rl, absolute_rl);
903 }
904
905 static bool is_ptr_subtract(struct expression *expr)
906 {
907 expr = strip_expr(expr);
908 if (!expr)
909 return false;
910 if (expr->type == EXPR_BINOP && expr->op == '-' &&
911 type_is_ptr(get_type(expr->left))) {
912 return true;
913 }
914 return false;
915 }
916
917 int get_user_rl(struct expression *expr, struct range_list **rl)
918 {
919 int user_data, no_user_data;
920
921 if (!expr)
922 return 0;
923
924 if (__in_fake_struct_assign &&
925 !has_states(__get_cur_stree(), my_id))
926 return 0;
927
928 if (is_ptr_subtract(expr))
929 return 0;
930
931 push_int(&user_data_flags, 0);
932 push_int(&no_user_data_flags, 0);
933
934 custom_get_absolute_rl(expr, &var_user_rl, rl);
935
936 user_data = pop_int(&user_data_flags);
937 no_user_data = pop_int(&no_user_data_flags);
938
939 if (!user_data || no_user_data)
940 *rl = NULL;
941
942 return !!*rl;
943 }
944
945 int is_user_rl(struct expression *expr)
946 {
947 struct range_list *tmp;
948
949 return get_user_rl(expr, &tmp) && tmp;
950 }
951
952 int get_user_rl_var_sym(const char *name, struct symbol *sym, struct range_list **rl)
953 {
954 struct smatch_state *state, *extra;
955
956 state = get_state(my_id, name, sym);
957 if (!estate_rl(state))
958 return 0;
959 *rl = estate_rl(state);
960
961 extra = get_state(SMATCH_EXTRA, name, sym);
962 if (estate_rl(extra))
963 *rl = rl_intersection(estate_rl(state), estate_rl(extra));
964
965 return 1;
966 }
967
968 bool is_socket_stuff(struct symbol *sym)
969 {
970 struct symbol *type;
971
972 /* This is a hack.
973 * Basically I never want to consider an skb or sk as user pointer.
974 * The skb->data is already marked as a source of user data, and if
975 * anything else is marked as user data it's almost certainly wrong.
976 *
977 * Ideally, I would figure out where this bogus data is coming from,
978 * but possibly it just was stuck in the database from previous updates
979 * and can't get cleared out without deleting all user data. Things
980 * like this gets stuck in the DB because of recursion.
981 *
982 * I could make this a temporary hack, but I keep wanting to do it so
983 * I'm just going to make it permanent. It either doesn't change
984 * anything or it makes life better.
985 */
986
987 type = get_real_base_type(sym);
988 if (!type || type->type != SYM_PTR)
989 return false;
990 type = get_real_base_type(type);
991 if (!type || type->type != SYM_STRUCT || !type->ident)
992 return false;
993
994 if (strcmp(type->ident->name, "sk_buff") == 0)
995 return true;
996 if (strcmp(type->ident->name, "sock") == 0)
997 return true;
998 if (strcmp(type->ident->name, "socket") == 0)
999 return true;
1000
1001 return false;
1002 }
1003
1004 static void return_info_callback(int return_id, char *return_ranges,
1005 struct expression *returned_expr,
1006 int param,
1007 const char *printed_name,
1008 struct sm_state *sm)
1009 {
1010 struct smatch_state *extra;
1011 struct range_list *rl;
1012 char buf[64];
1013
1014 if (is_socket_stuff(sm->sym))
1015 return;
1016 if (is_ignored_kernel_data(printed_name))
1017 return;
1018
1019 if (param >= 0) {
1020 if (strcmp(printed_name, "$") == 0)
1021 return;
1022 if (!estate_assigned(sm->state) &&
1023 !estate_new(sm->state))
1024 return;
1025 }
1026 rl = estate_rl(sm->state);
1027 if (!rl)
1028 return;
1029 extra = get_state(SMATCH_EXTRA, sm->name, sm->sym);
1030 if (estate_rl(extra))
1031 rl = rl_intersection(estate_rl(sm->state), estate_rl(extra));
1032 if (!rl)
1033 return;
1034
1035 snprintf(buf, sizeof(buf), "%s%s%s",
1036 show_rl(rl),
1037 estate_capped(sm->state) ? "[c]" : "",
1038 estate_treat_untagged(sm->state) ? "[u]" : "");
1039 sql_insert_return_states(return_id, return_ranges,
1040 estate_new(sm->state) ? USER_DATA_SET : USER_DATA,
1041 param, printed_name, buf);
1042 }
1043
1044 static bool is_ignored_macro(struct position pos)
1045 {
1046 const char *macro;
1047
1048 macro = get_macro_name(pos);
1049 if (!macro)
1050 return false;
1051 if (strcmp(macro, "v4l2_subdev_call") == 0)
1052 return true;
1053 return false;
1054 }
1055
1056 static void caller_info_callback(struct expression *call, int param, char *printed_name, struct sm_state *sm)
1057 {
1058 struct smatch_state *state;
1059 struct range_list *rl;
1060 struct symbol *type;
1061 char buf[64];
1062
1063 if (is_ignored_macro(call->pos))
1064 return;
1065
1066 if (is_socket_stuff(sm->sym))
1067 return;
1068 if (is_ignored_kernel_data(printed_name))
1069 return;
1070
1071 /*
1072 * Smatch uses a hack where if we get an unsigned long we say it's
1073 * both user data and it points to user data. But if we pass it to a
1074 * function which takes an int, then it's just user data. There's not
1075 * enough bytes for it to be a pointer.
1076 *
1077 */
1078 type = get_arg_type(call->fn, param);
1079 if (strcmp(printed_name, "$") != 0 && type && type_bits(type) < type_bits(&ptr_ctype))
1080 return;
1081
1082 if (strcmp(sm->state->name, "") == 0)
1083 return;
1084
1085 state = __get_state(SMATCH_EXTRA, sm->name, sm->sym);
1086 if (!state || !estate_rl(state))
1087 rl = estate_rl(sm->state);
1088 else
1089 rl = rl_intersection(estate_rl(sm->state), estate_rl(state));
1090
1091 if (!rl)
1092 return;
1093
1094 snprintf(buf, sizeof(buf), "%s%s%s", show_rl(rl),
1095 estate_capped(sm->state) ? "[c]" : "",
1096 estate_treat_untagged(sm->state) ? "[u]" : "");
1097 sql_insert_caller_info(call, USER_DATA, param, printed_name, buf);
1098 }
1099
1100 static void db_param_set(struct expression *expr, int param, char *key, char *value)
1101 {
1102 struct expression *arg;
1103 char *name;
1104 struct symbol *sym;
1105 struct smatch_state *state;
1106
1107 while (expr->type == EXPR_ASSIGNMENT)
1108 expr = strip_expr(expr->right);
1109 if (expr->type != EXPR_CALL)
1110 return;
1111 if (expr == ignore_clear)
1112 return;
1113
1114 arg = get_argument_from_call_expr(expr->args, param);
1115 if (!arg)
1116 return;
1117 name = get_variable_from_key(arg, key, &sym);
1118 if (!name || !sym)
1119 goto free;
1120
1121 state = get_state(my_id, name, sym);
1122 if (!state)
1123 goto free;
1124
1125 set_state(my_id, name, sym, alloc_estate_empty());
1126 free:
1127 free_string(name);
1128 }
1129
1130 static bool param_data_capped(const char *value)
1131 {
1132 if (strstr(value, ",c") || strstr(value, "[c"))
1133 return true;
1134 return false;
1135 }
1136
1137 static bool param_data_treat_untagged(const char *value)
1138 {
1139 if (strstr(value, ",u") || strstr(value, "[u"))
1140 return true;
1141 return false;
1142 }
1143
1144 static void set_param_user_data(const char *name, struct symbol *sym, char *key, char *value)
1145 {
1146 struct expression *expr;
1147 struct range_list *rl = NULL;
1148 struct smatch_state *state;
1149 struct symbol *type;
1150 char *fullname;
1151
1152 expr = symbol_expression(sym);
1153 fullname = get_variable_from_key(expr, key, NULL);
1154 if (!fullname)
1155 return;
1156
1157 type = get_member_type_from_key(expr, key);
1158 if (type && type->type == SYM_STRUCT)
1159 return;
1160
1161 if (!type)
1162 return;
1163
1164 str_to_rl(type, value, &rl);
1165 rl = swap_mtag_seed(expr, rl);
1166 state = alloc_estate_rl(rl);
1167 if (param_data_capped(value) || is_capped(expr))
1168 estate_set_capped(state);
1169 if (param_data_treat_untagged(value) || sym->ctype.as == 5)
1170 estate_set_treat_untagged(state);
1171 set_state(my_id, fullname, sym, state);
1172 }
1173
1174 static void set_called(const char *name, struct symbol *sym, char *key, char *value)
1175 {
1176 set_state(my_call_id, "this_function", NULL, &called);
1177 }
1178
1179 static void match_syscall_definition(struct symbol *sym)
1180 {
1181 struct symbol *arg;
1182 char *macro;
1183 char *name;
1184 int is_syscall = 0;
1185
1186 macro = get_macro_name(sym->pos);
1187 if (macro &&
1188 (strncmp("SYSCALL_DEFINE", macro, strlen("SYSCALL_DEFINE")) == 0 ||
1189 strncmp("COMPAT_SYSCALL_DEFINE", macro, strlen("COMPAT_SYSCALL_DEFINE")) == 0))
1190 is_syscall = 1;
1191
1192 name = get_function();
1193 if (!option_no_db && get_state(my_call_id, "this_function", NULL) != &called) {
1194 if (name && strncmp(name, "sys_", 4) == 0)
1195 is_syscall = 1;
1196 }
1197
1198 if (name && strncmp(name, "compat_sys_", 11) == 0)
1199 is_syscall = 1;
1200
1201 if (!is_syscall)
1202 return;
1203
1204 FOR_EACH_PTR(sym->ctype.base_type->arguments, arg) {
1205 set_state(my_id, arg->ident->name, arg, alloc_estate_whole(get_real_base_type(arg)));
1206 } END_FOR_EACH_PTR(arg);
1207 }
1208
1209 #define OLD 0
1210 #define NEW 1
1211
1212 static void store_user_data_return(struct expression *expr, char *key, char *value, bool is_new)
1213 {
1214 struct smatch_state *state;
1215 struct range_list *rl;
1216 struct symbol *type;
1217 char buf[48];
1218
1219 if (key[0] != '$')
1220 return;
1221
1222 type = get_type(expr);
1223 snprintf(buf, sizeof(buf), "return %p%s", expr, key + 1);
1224 call_results_to_rl(expr, type, value, &rl);
1225
1226 state = alloc_estate_rl(rl);
1227 if (is_new)
1228 estate_set_new(state);
1229
1230 set_state(my_id, buf, NULL, state);
1231 }
1232
1233 // FIXME: not a fan of this name, would prefer set_to_user_data() but that's
1234 // already used.
1235 void mark_as_user_data(struct expression *expr, bool isnew)
1236 {
1237 struct smatch_state *state;
1238
1239 state = alloc_estate_whole(get_type(expr));
1240 if (isnew) {
1241 func_gets_user_data = true;
1242 estate_set_new(state);
1243 }
1244 set_state_expr(my_id, expr, state);
1245 }
1246
1247 static void set_to_user_data(struct expression *expr, char *key, char *value, bool is_new)
1248 {
1249 struct smatch_state *state;
1250 char *name;
1251 struct symbol *sym;
1252 struct symbol *type;
1253 struct range_list *rl = NULL;
1254
1255 type = get_member_type_from_key(expr, key);
1256 name = get_variable_from_key(expr, key, &sym);
1257 if (!name || !sym)
1258 goto free;
1259
1260 call_results_to_rl(expr, type, value, &rl);
1261
1262 state = alloc_estate_rl(rl);
1263 if (param_data_capped(value))
1264 estate_set_capped(state);
1265 if (param_data_treat_untagged(value))
1266 estate_set_treat_untagged(state);
1267 if (is_new)
1268 estate_set_new(state);
1269 estate_set_assigned(state);
1270 set_state(my_id, name, sym, state);
1271 free:
1272 free_string(name);
1273 }
1274
1275 static void returns_param_user_data(struct expression *expr, int param, char *key, char *value)
1276 {
1277 struct expression *arg;
1278 struct expression *call;
1279
1280 call = expr;
1281 while (call->type == EXPR_ASSIGNMENT)
1282 call = strip_expr(call->right);
1283 if (call->type != EXPR_CALL)
1284 return;
1285
1286 if (!we_pass_user_data(call))
1287 return;
1288
1289 if (param == -1) {
1290 if (expr->type != EXPR_ASSIGNMENT) {
1291 // TODO: faked_assign this should all be handled as a fake assignment
1292 store_user_data_return(expr, key, value, OLD);
1293 return;
1294 }
1295 set_to_user_data(expr->left, key, value, OLD);
1296 return;
1297 }
1298
1299 arg = get_argument_from_call_expr(call->args, param);
1300 if (!arg)
1301 return;
1302 set_to_user_data(arg, key, value, OLD);
1303 }
1304
1305 static void returns_param_user_data_set(struct expression *expr, int param, char *key, char *value)
1306 {
1307 struct expression *arg;
1308
1309 func_gets_user_data = true;
1310
1311 if (param == -1) {
1312 if (expr->type != EXPR_ASSIGNMENT) {
1313 store_user_data_return(expr, key, value, NEW);
1314 return;
1315 }
1316 set_to_user_data(expr->left, key, value, NEW);
1317 return;
1318 }
1319
1320 while (expr->type == EXPR_ASSIGNMENT)
1321 expr = strip_expr(expr->right);
1322 if (expr->type != EXPR_CALL)
1323 return;
1324
1325 arg = get_argument_from_call_expr(expr->args, param);
1326 if (!arg)
1327 return;
1328 set_to_user_data(arg, key, value, NEW);
1329 }
1330
1331 static void set_param_key_user_data(struct expression *expr, const char *name,
1332 struct symbol *sym, void *data)
1333 {
1334 struct expression *arg;
1335
1336 func_gets_user_data = true;
1337 arg = gen_expression_from_name_sym(name, sym);
1338 set_state_expr(my_id, arg, new_state(get_type(arg)));
1339 }
1340
1341 static void match_capped(struct expression *expr, const char *name, struct symbol *sym, void *info)
1342 {
1343 struct smatch_state *state, *new;
1344
1345 state = get_state(my_id, name, sym);
1346 if (!state || estate_capped(state))
1347 return;
1348
1349 new = clone_estate(state);
1350 estate_set_capped(new);
1351
1352 set_state(my_id, name, sym, new);
1353 }
1354
1355 void register_kernel_user_data(int id)
1356 {
1357 struct user_fn_info *info;
1358 int i;
1359
1360 my_id = id;
1361
1362 if (option_project != PROJ_KERNEL)
1363 return;
1364
1365 set_dynamic_states(my_id);
1366
1367 add_function_data(&func_gets_user_data);
1368
1369 add_unmatched_state_hook(my_id, &empty_state);
1370 add_extra_nomod_hook(&extra_nomod_hook);
1371 add_pre_merge_hook(my_id, &pre_merge_hook);
1372 add_merge_hook(my_id, &merge_estates);
1373
1374 add_function_hook("sscanf", &match_sscanf, NULL);
1375
1376 add_hook(&match_syscall_definition, AFTER_DEF_HOOK);
1377
1378 add_hook(&match_assign, ASSIGNMENT_HOOK);
1379 select_return_states_hook(PARAM_SET, &db_param_set);
1380 add_hook(&match_condition, CONDITION_HOOK);
1381
1382 add_caller_info_callback(my_id, caller_info_callback);
1383 add_return_info_callback(my_id, return_info_callback);
1384 select_caller_info_hook(set_param_user_data, USER_DATA);
1385 select_return_states_hook(USER_DATA, &returns_param_user_data);
1386 select_return_states_hook(USER_DATA_SET, &returns_param_user_data_set);
1387
1388 select_return_param_key(CAPPED_DATA, &match_capped);
1389 add_function_param_key_hook_late("memcpy", &match_capped, 2, "$", NULL);
1390 add_function_param_key_hook_late("_memcpy", &match_capped, 2, "$", NULL);
1391 add_function_param_key_hook_late("__memcpy", &match_capped, 2, "$", NULL);
1392 add_function_param_key_hook_late("memset", &match_capped, 2, "$", NULL);
1393 add_function_param_key_hook_late("_memset", &match_capped, 2, "$", NULL);
1394 add_function_param_key_hook_late("__memset", &match_capped, 2, "$", NULL);
1395
1396 for (i = 0; i < ARRAY_SIZE(func_table); i++) {
1397 info = &func_table[i];
1398 add_function_param_key_hook_late(info->name, &set_param_key_user_data,
1399 info->param, info->key, info);
1400 }
1401 }
1402
1403 void register_kernel_user_data2(int id)
1404 {
1405 my_call_id = id;
1406
1407 if (option_project != PROJ_KERNEL)
1408 return;
1409 select_caller_info_hook(set_called, INTERNAL);
1410 }
Static analysis for C