1 /*
2 * Copyright (C) 2009 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 #include "smatch_slist.h"
20 #include "smatch_extra.h"
21
22 static int my_id;
23
24 STATE(err_ptr);
25 STATE(checked);
26
27 static sval_t err_ptr_min = {
28 .type = &int_ctype,
29 {.value = -4095},
30 };
31
32 static sval_t err_ptr_max = {
33 .type = &int_ctype,
34 {.value = -1},
35 };
36
37 struct range_list *err_ptr_rl;
38
ok_to_use(struct sm_state * sm,struct expression * mod_expr)39 static void ok_to_use(struct sm_state *sm, struct expression *mod_expr)
40 {
41 if (sm->state != &checked)
42 set_state(my_id, sm->name, sm->sym, &checked);
43 }
44
check_is_err_ptr(struct expression * expr)45 static void check_is_err_ptr(struct expression *expr)
46 {
47 struct sm_state *sm;
48 struct range_list *rl;
49
50 sm = get_sm_state_expr(my_id, expr);
51 if (!sm)
52 return;
53
54 if (!slist_has_state(sm->possible, &err_ptr))
55 return;
56
57 get_absolute_rl(expr, &rl);
58 if (!possibly_true_rl(rl, SPECIAL_EQUAL, err_ptr_rl))
59 return;
60
61 sm_error("'%s' dereferencing possible ERR_PTR()", sm->name);
62 set_state(my_id, sm->name, sm->sym, &checked);
63 }
64
match_returns_err_ptr(const char * fn,struct expression * expr,void * info)65 static void match_returns_err_ptr(const char *fn, struct expression *expr,
66 void *info)
67 {
68 set_state_expr(my_id, expr->left, &err_ptr);
69 }
70
set_param_dereferenced(struct expression * call,struct expression * arg,char * key,char * unused)71 static void set_param_dereferenced(struct expression *call, struct expression *arg, char *key, char *unused)
72 {
73 struct sm_state *sm;
74 struct smatch_state *estate;
75 struct symbol *sym;
76 char *name;
77
78 name = get_variable_from_key(arg, key, &sym);
79 if (!name || !sym)
80 goto free;
81
82 sm = get_sm_state(my_id, name, sym);
83 if (!sm)
84 goto free;
85
86 if (!slist_has_state(sm->possible, &err_ptr))
87 goto free;
88
89 estate = get_state(SMATCH_EXTRA, name, sym);
90 if (!estate || !possibly_true_rl(estate_rl(estate), SPECIAL_EQUAL, err_ptr_rl))
91 goto free;
92
93 sm_error("'%s' dereferencing possible ERR_PTR()", sm->name);
94 set_state(my_id, sm->name, sm->sym, &checked);
95
96 free:
97 free_string(name);
98 }
99
match_checked(const char * fn,struct expression * call_expr,struct expression * assign_expr,void * unused)100 static void match_checked(const char *fn, struct expression *call_expr,
101 struct expression *assign_expr, void *unused)
102 {
103 struct expression *arg;
104
105 arg = get_argument_from_call_expr(call_expr->args, 0);
106 arg = strip_expr(arg);
107 while (arg->type == EXPR_ASSIGNMENT)
108 arg = strip_expr(arg->left);
109 set_state_expr(my_id, arg, &checked);
110 }
111
match_err(const char * fn,struct expression * call_expr,struct expression * assign_expr,void * unused)112 static void match_err(const char *fn, struct expression *call_expr,
113 struct expression *assign_expr, void *unused)
114 {
115 struct expression *arg;
116
117 arg = get_argument_from_call_expr(call_expr->args, 0);
118 arg = strip_expr(arg);
119 while (arg->type == EXPR_ASSIGNMENT)
120 arg = strip_expr(arg->left);
121 set_state_expr(my_id, arg, &err_ptr);
122 }
123
match_dereferences(struct expression * expr)124 static void match_dereferences(struct expression *expr)
125 {
126 if (expr->type != EXPR_PREOP)
127 return;
128 check_is_err_ptr(expr->unop);
129 }
130
match_kfree(const char * fn,struct expression * expr,void * _arg_nr)131 static void match_kfree(const char *fn, struct expression *expr, void *_arg_nr)
132 {
133 int arg_nr = PTR_INT(_arg_nr);
134 struct expression *arg;
135
136 arg = get_argument_from_call_expr(expr->args, arg_nr);
137 check_is_err_ptr(arg);
138 }
139
match_condition(struct expression * expr)140 static void match_condition(struct expression *expr)
141 {
142 if (expr->type == EXPR_ASSIGNMENT) {
143 match_condition(expr->right);
144 match_condition(expr->left);
145 }
146 if (!get_state_expr(my_id, expr))
147 return;
148 /* If we know the variable is zero that means it's not an ERR_PTR */
149 set_true_false_states_expr(my_id, expr, NULL, &checked);
150 }
151
register_err_ptr_funcs(void)152 static void register_err_ptr_funcs(void)
153 {
154 struct token *token;
155 const char *func;
156
157 token = get_tokens_file("kernel.returns_err_ptr");
158 if (!token)
159 return;
160 if (token_type(token) != TOKEN_STREAMBEGIN)
161 return;
162 token = token->next;
163 while (token_type(token) != TOKEN_STREAMEND) {
164 if (token_type(token) != TOKEN_IDENT)
165 return;
166 func = show_ident(token->ident);
167 add_function_assign_hook(func, &match_returns_err_ptr, NULL);
168 token = token->next;
169 }
170 clear_token_alloc();
171 }
172
match_err_ptr_positive_const(const char * fn,struct expression * expr,void * unused)173 static void match_err_ptr_positive_const(const char *fn, struct expression *expr, void *unused)
174 {
175 struct expression *arg;
176 sval_t sval;
177
178 arg = get_argument_from_call_expr(expr->args, 0);
179
180 if (!get_value(arg, &sval))
181 return;
182 if (sval_is_positive(sval) && sval_cmp_val(sval, 0) != 0)
183 sm_error("passing non negative %s to ERR_PTR", sval_to_str(sval));
184 }
185
match_err_ptr(const char * fn,struct expression * expr,void * unused)186 static void match_err_ptr(const char *fn, struct expression *expr, void *unused)
187 {
188 struct expression *arg;
189 struct sm_state *sm;
190 struct sm_state *tmp;
191 sval_t tmp_min;
192 sval_t tmp_max;
193 sval_t min = sval_type_max(&llong_ctype);
194 sval_t max = sval_type_min(&llong_ctype);
195
196 arg = get_argument_from_call_expr(expr->args, 0);
197 sm = get_sm_state_expr(SMATCH_EXTRA, arg);
198 if (!sm)
199 return;
200 FOR_EACH_PTR(sm->possible, tmp) {
201 tmp_min = estate_min(tmp->state);
202 if (!sval_is_a_min(tmp_min) && sval_cmp(tmp_min, min) < 0)
203 min = tmp_min;
204 tmp_max = estate_max(tmp->state);
205 if (!sval_is_a_max(tmp_max) && sval_cmp(tmp_max, max) > 0)
206 max = tmp_max;
207 } END_FOR_EACH_PTR(tmp);
208 if (sval_is_negative(min) && sval_cmp_val(min, -4095) < 0)
209 sm_error("%s too low for ERR_PTR", sval_to_str(min));
210 if (sval_is_positive(max) && sval_cmp_val(max, 0) != 0)
211 sm_error("passing non negative %s to ERR_PTR", sval_to_str(max));
212 }
213
check_err_ptr_deref(int id)214 void check_err_ptr_deref(int id)
215 {
216 if (option_project != PROJ_KERNEL)
217 return;
218
219 my_id = id;
220 return_implies_state("IS_ERR", 0, 0, &match_checked, NULL);
221 return_implies_state("IS_ERR", 1, 1, &match_err, NULL);
222 return_implies_state("IS_ERR_OR_NULL", 0, 0, &match_checked, NULL);
223 return_implies_state("IS_ERR_OR_NULL", 1, 1, &match_err, NULL);
224 return_implies_state("PTR_RET", 0, 0, &match_checked, NULL);
225 return_implies_state("PTR_RET", -4095, -1, &match_err, NULL);
226 register_err_ptr_funcs();
227 add_hook(&match_dereferences, DEREF_HOOK);
228 add_function_hook("ERR_PTR", &match_err_ptr_positive_const, NULL);
229 add_function_hook("ERR_PTR", &match_err_ptr, NULL);
230 add_hook(&match_condition, CONDITION_HOOK);
231 add_modification_hook(my_id, &ok_to_use);
232 add_function_hook("kfree", &match_kfree, INT_PTR(0));
233 add_function_hook("brelse", &match_kfree, INT_PTR(0));
234 add_function_hook("kmem_cache_free", &match_kfree, INT_PTR(1));
235 add_function_hook("vfree", &match_kfree, INT_PTR(0));
236
237 err_ptr_rl = clone_rl_permanent(alloc_rl(err_ptr_min, err_ptr_max));
238
239 select_return_implies_hook(DEREFERENCE, &set_param_dereferenced);
240 }
241
242