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/*
19 * This file is sort of like check_dereferences_param.c.  In theory the one
20 * difference should be that the param is NULL it should still be counted as a
21 * free.  But for now I don't handle that case.
22 */
23
24#include "smatch.h"
25#include "smatch_extra.h"
26#include "smatch_slist.h"
27
28static int my_id;
29
30STATE(freed);
31STATE(ignore);
32
33static struct smatch_state *unmatched_state(struct sm_state *sm)
34{
35	if (sm->state != &freed)
36		return &undefined;
37	if (parent_is_null_var_sym(sm->name, sm->sym))
38		return &freed;
39	return &undefined;
40}
41
42static void set_ignore(struct sm_state *sm, struct expression *mod_expr)
43{
44	set_state(my_id, sm->name, sm->sym, &ignore);
45}
46
47static int counter_was_inced(struct expression *expr)
48{
49	char *name;
50	struct symbol *sym;
51	char buf[256];
52	int ret = 0;
53
54	name = expr_to_var_sym(expr, &sym);
55	if (!name || !sym)
56		goto free;
57
58	snprintf(buf, sizeof(buf), "%s->users.counter", name);
59	ret = was_inced(buf, sym);
60free:
61	free_string(name);
62	return ret;
63}
64
65static void match_free(const char *fn, struct expression *expr, void *param)
66{
67	struct expression *arg, *tmp;
68	int cnt = 0;
69
70	arg = get_argument_from_call_expr(expr->args, PTR_INT(param));
71	if (!arg)
72		return;
73	while ((tmp = get_assigned_expr(arg))) {
74		arg = strip_expr(tmp);
75		if (cnt++ > 5)
76			break;
77	}
78
79	if (get_param_num(arg) < 0)
80		return;
81	if (param_was_set(arg))
82		return;
83	if (strcmp(fn, "kfree_skb") == 0 && counter_was_inced(arg))
84		return;
85
86	set_state_expr(my_id, arg, &freed);
87}
88
89static void set_param_freed(struct expression *expr, int param, char *key, char *value)
90{
91	struct expression *arg;
92	char *name;
93	struct symbol *sym;
94
95	while (expr->type == EXPR_ASSIGNMENT)
96		expr = strip_expr(expr->right);
97	if (expr->type != EXPR_CALL)
98		return;
99
100	arg = get_argument_from_call_expr(expr->args, param);
101	if (!arg)
102		return;
103	name = get_variable_from_key(arg, key, &sym);
104	if (!name || !sym)
105		goto free;
106	if (get_param_num_from_sym(sym) < 0)
107		goto free;
108
109	if (param_was_set_var_sym(name, sym))
110		goto free;
111
112	set_state(my_id, name, sym, &freed);
113free:
114	free_string(name);
115}
116
117static void param_freed_info(int return_id, char *return_ranges, struct expression *expr)
118{
119	struct sm_state *sm;
120	int param;
121	const char *param_name;
122
123	if (on_atomic_dec_path())
124		return;
125
126	FOR_EACH_MY_SM(my_id, __get_cur_stree(), sm) {
127		if (sm->state != &freed)
128			continue;
129
130		param = get_param_num_from_sym(sm->sym);
131		if (param < 0)
132			continue;
133
134		param_name = get_param_name(sm);
135		if (!param_name)
136			continue;
137
138		sql_insert_return_states(return_id, return_ranges, PARAM_FREED,
139					 param, param_name, "");
140	} END_FOR_EACH_SM(sm);
141}
142
143void check_frees_param_strict(int id)
144{
145	my_id = id;
146
147	if (option_project != PROJ_KERNEL)
148		return;
149
150	add_function_hook("kfree", &match_free, INT_PTR(0));
151	add_function_hook("kmem_cache_free", &match_free, INT_PTR(1));
152	add_function_hook("kfree_skb", &match_free, INT_PTR(0));
153	add_function_hook("kfree_skbmem", &match_free, INT_PTR(0));
154	add_function_hook("dma_pool_free", &match_free, INT_PTR(1));
155	add_function_hook("spi_unregister_controller", &match_free, INT_PTR(0));
156
157	select_return_states_hook(PARAM_FREED, &set_param_freed);
158	add_modification_hook(my_id, &set_ignore);
159	add_split_return_callback(&param_freed_info);
160
161	add_unmatched_state_hook(my_id, &unmatched_state);
162}
163