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 
match_snprintf(const char * fn,struct expression * expr,void * unused)20 static void match_snprintf(const char *fn, struct expression *expr, void *unused)
21 {
22 	struct expression *dest;
23 	struct expression *dest_size_expr;
24 	struct expression *format_string;
25 	struct expression *data;
26 	char *data_name = NULL;
27 	int dest_size;
28 	sval_t limit_size;
29 	char *format;
30 	int data_size;
31 
32 	dest = get_argument_from_call_expr(expr->args, 0);
33 	dest_size_expr = get_argument_from_call_expr(expr->args, 1);
34 	format_string = get_argument_from_call_expr(expr->args, 2);
35 	data = get_argument_from_call_expr(expr->args, 3);
36 
37 	dest_size = get_array_size_bytes(dest);
38 	if (!get_implied_value(dest_size_expr, &limit_size))
39 		return;
40 	if (dest_size > 1 && dest_size < limit_size.value)
41 		sm_error("snprintf() is printing too much %s vs %d",
42 			 sval_to_str(limit_size), dest_size);
43 	format = expr_to_var(format_string);
44 	if (!format)
45 		return;
46 	if (strcmp(format, "\"%s\""))
47 		goto free;
48 	data_name = expr_to_str(data);
49 	data_size = get_size_from_strlen(data);
50 	if (!data_size)
51 		data_size = get_array_size_bytes(data);
52 	if (limit_size.value < data_size)
53 		sm_error("snprintf() chops off the last chars of '%s': %d vs %s",
54 		       data_name, data_size, sval_to_str(limit_size));
55 free:
56 	free_string(data_name);
57 	free_string(format);
58 }
59 
check_snprintf_overflow(int id)60 void check_snprintf_overflow(int id)
61 {
62 	add_function_hook("snprintf", &match_snprintf, NULL);
63 }
64