1 /*
2 * Copyright (C) 2014 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 #include "smatch.h"
19
20 static int my_id;
21
22 STATE(too_small);
23
match_assign(struct expression * expr)24 static void match_assign(struct expression *expr)
25 {
26 struct symbol *left_type, *right_type;
27 struct expression *size_expr;
28 sval_t min_size;
29 int limit_type;
30 int bytes;
31
32 left_type = get_type(expr->left);
33 if (!left_type || left_type->type != SYM_PTR)
34 return;
35 left_type = get_real_base_type(left_type);
36 if (!left_type || left_type->type != SYM_STRUCT)
37 return;
38
39 right_type = get_type(expr->right);
40 if (!right_type || right_type->type != SYM_PTR)
41 return;
42 right_type = get_real_base_type(right_type);
43 if (!right_type)
44 return;
45 if (right_type != &void_ctype && type_bits(right_type) != 8)
46 return;
47
48 bytes = get_array_size_bytes(expr->right);
49 if (bytes >= type_bytes(left_type))
50 return;
51
52 size_expr = get_size_variable(expr->right, &limit_type);
53 if (!size_expr)
54 return;
55 if (limit_type != ELEM_COUNT)
56 return;
57
58 get_absolute_min(size_expr, &min_size);
59 if (min_size.value >= type_bytes(left_type))
60 return;
61
62 set_state_expr(my_id, expr->left, &too_small);
63 }
64
match_dereferences(struct expression * expr)65 static void match_dereferences(struct expression *expr)
66 {
67 struct symbol *left_type;
68 struct expression *right;
69 struct smatch_state *state;
70 char *name;
71 struct expression *size_expr;
72 sval_t min_size;
73 int limit_type;
74
75 if (expr->type != EXPR_PREOP)
76 return;
77
78 expr = strip_expr(expr->unop);
79 state = get_state_expr(my_id, expr);
80 if (state != &too_small)
81 return;
82
83 left_type = get_type(expr);
84 if (!left_type || left_type->type != SYM_PTR)
85 return;
86 left_type = get_real_base_type(left_type);
87 if (!left_type || left_type->type != SYM_STRUCT)
88 return;
89
90 right = get_assigned_expr(expr);
91 size_expr = get_size_variable(right, &limit_type);
92 if (!size_expr)
93 return;
94 if (limit_type != ELEM_COUNT)
95 return;
96
97 get_absolute_min(size_expr, &min_size);
98 if (min_size.value >= type_bytes(left_type))
99 return;
100
101 name = expr_to_str(right);
102 sm_warning("is '%s' large enough for 'struct %s'? %s", name, left_type->ident ? left_type->ident->name : "<anon>", sval_to_str(min_size));
103 free_string(name);
104 set_state_expr(my_id, expr, &undefined);
105 }
106
check_buffer_too_small_for_struct(int id)107 void check_buffer_too_small_for_struct(int id)
108 {
109 my_id = id;
110
111 add_hook(&match_assign, ASSIGNMENT_HOOK);
112 add_hook(&match_dereferences, DEREF_HOOK);
113 }
114