1 /*
2  * Copyright (C) 2010 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 #include <stdlib.h>
19 #include "parse.h"
20 #include "smatch.h"
21 #include "smatch_slist.h"
22 #include "smatch_extra.h"
23 
24 /*
25  * This check has two smatch IDs.
26  * my_used_id - keeps a record of array offsets that have been used.
27  *              If the code checks that they are within bounds later on,
28  *              we complain about using an array offset before checking
29  *              that it is within bounds.
30  */
31 static int my_used_id;
32 
33 static void delete(struct sm_state *sm, struct expression *mod_expr)
34 {
35 	set_state(my_used_id, sm->name, sm->sym, &undefined);
36 }
37 
38 static void array_check(struct expression *expr)
39 {
40 	struct expression *array_expr;
41 	int array_size;
42 	struct expression *offset;
43 	struct range_list *rl;
44 
45 	expr = strip_expr(expr);
46 	if (!is_array(expr))
47 		return;
48 
49 	array_expr = get_array_base(expr);
50 	array_size = get_array_size(array_expr);
51 	if (!array_size || array_size == 1)
52 		return;
53 
54 	offset = get_array_offset(expr);
55 	get_absolute_rl(offset, &rl);
56 	if (rl_max(rl).uvalue < array_size)
57 		return;
58 	if (buf_comparison_index_ok(expr))
59 		return;
60 
61 	if (getting_address(expr))
62 		return;
63 	if (is_capped(offset))
64 		return;
65 	set_state_expr(my_used_id, offset, alloc_state_num(array_size));
66 }
67 
68 static void match_condition(struct expression *expr)
69 {
70 	int left;
71 	sval_t sval;
72 	struct state_list *slist;
73 	struct sm_state *tmp;
74 	int boundary;
75 
76 	if (!expr || expr->type != EXPR_COMPARE)
77 		return;
78 	if (get_macro_name(expr->pos))
79 		return;
80 	if (get_implied_value(expr->left, &sval))
81 		left = 1;
82 	else if (get_implied_value(expr->right, &sval))
83 		left = 0;
84 	else
85 		return;
86 
87 	if (left)
88 		slist = get_possible_states_expr(my_used_id, expr->right);
89 	else
90 		slist = get_possible_states_expr(my_used_id, expr->left);
91 	if (!slist)
92 		return;
93 	FOR_EACH_PTR(slist, tmp) {
94 		if (tmp->state == &merged || tmp->state == &undefined)
95 			continue;
96 		boundary = PTR_INT(tmp->state->data);
97 		boundary -= sval.value;
98 		if (boundary < 1 && boundary > -1) {
99 			char *name;
100 
101 			name = expr_to_var(left ? expr->right : expr->left);
102 			sm_error("testing array offset '%s' after use.", name);
103 			return;
104 		}
105 	} END_FOR_EACH_PTR(tmp);
106 }
107 
108 void check_testing_index_after_use(int id)
109 {
110 	my_used_id = id;
111 	set_dynamic_states(my_used_id);
112 	add_hook(&array_check, OP_HOOK);
113 	add_hook(&match_condition, CONDITION_HOOK);
114 	add_modification_hook(my_used_id, &delete);
115 }
116