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 "smatch.h"
19
20 static int my_id;
21
can_overflow(struct expression * expr)22 static int can_overflow(struct expression *expr)
23 {
24 sval_t max;
25 int uncapped = 0;
26
27 expr = strip_expr(expr);
28
29 if (expr->type == EXPR_BINOP) {
30 uncapped += can_overflow(expr->left);
31 uncapped += can_overflow(expr->right);
32
33 if (uncapped &&
34 (expr->op == '+' || expr->op == '*' || expr->op == SPECIAL_LEFTSHIFT))
35 return 1;
36
37 return 0;
38 }
39
40 if (get_implied_max(expr, &max))
41 return 0;
42 if (get_absolute_max(expr, &max) && sval_cmp_val(max, 4096) <= 0)
43 return 0;
44 return 1;
45 }
46
match_size(struct expression * size_expr)47 static void match_size(struct expression *size_expr)
48 {
49 char *name;
50
51 size_expr = strip_expr(size_expr);
52 if (!size_expr)
53 return;
54 if (size_expr->type != EXPR_BINOP) {
55 size_expr = get_assigned_expr(size_expr);
56 if (!size_expr || size_expr->type != EXPR_BINOP)
57 return;
58 }
59 if (!can_overflow(size_expr))
60 return;
61
62 name = expr_to_str(size_expr);
63 sm_warning("math in access_ok() is dangerous '%s'", name);
64
65 free_string(name);
66 }
67
match_access_ok(const char * fn,struct expression * expr,void * data)68 static void match_access_ok(const char *fn, struct expression *expr, void *data)
69 {
70 struct expression *size_expr;
71
72 size_expr = get_argument_from_call_expr(expr->args, 1);
73 match_size(size_expr);
74 }
75
split_asm_constraints(struct expression_list * expr_list)76 static void split_asm_constraints(struct expression_list *expr_list)
77 {
78 struct expression *expr;
79 int i;
80
81 i = 0;
82 FOR_EACH_PTR(expr_list, expr) {
83 i++;
84 if (expr->type != EXPR_ASM_OPERAND)
85 continue;
86 if (i == 1)
87 match_size(expr->expr);
88 } END_FOR_EACH_PTR(expr);
89 }
90
match_asm_stmt(struct statement * stmt)91 static void match_asm_stmt(struct statement *stmt)
92 {
93 char *name;
94
95 name = get_macro_name(stmt->pos);
96 if (!name || strcmp(name, "access_ok") != 0)
97 return;
98 split_asm_constraints(stmt->asm_inputs);
99 }
100
check_access_ok_math(int id)101 void check_access_ok_math(int id)
102 {
103 my_id = id;
104 if (option_project != PROJ_KERNEL)
105 return;
106 if (!option_spammy)
107 return;
108 add_function_hook("__access_ok", &match_access_ok, NULL);
109 add_hook(&match_asm_stmt, ASM_HOOK);
110 }
111