check_err_ptr_deref.c

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