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 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
  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
  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
  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
  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
 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
 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
 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
 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
 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
 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
 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
 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
 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