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 sval_t err_ptr_min = {
  28         .type = &int_ctype,
  29         {.value = -4095},
  30 };
  31
  32 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_msg("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
  72 static void match_checked(const char *fn, struct expression *call_expr,
  73                         struct expression *assign_expr, void *unused)
  74 {
  75         struct expression *arg;
  76
  77         arg = get_argument_from_call_expr(call_expr->args, 0);
  78         arg = strip_expr(arg);
  79         while (arg->type == EXPR_ASSIGNMENT)
  80                 arg = strip_expr(arg->left);
  81         set_state_expr(my_id, arg, &checked);
  82 }
  83
  84 static void match_err(const char *fn, struct expression *call_expr,
  85                         struct expression *assign_expr, void *unused)
  86 {
  87         struct expression *arg;
  88
  89         arg = get_argument_from_call_expr(call_expr->args, 0);
  90         arg = strip_expr(arg);
  91         while (arg->type == EXPR_ASSIGNMENT)
  92                 arg = strip_expr(arg->left);
  93         set_state_expr(my_id, arg, &err_ptr);
  94 }
  95
  96 static void match_dereferences(struct expression *expr)
  97 {
  98         if (expr->type != EXPR_PREOP)
  99                 return;
 100         check_is_err_ptr(expr->unop);
 101 }
 102
 103 static void match_kfree(const char *fn, struct expression *expr, void *_arg_nr)
 104 {
 105         int arg_nr = PTR_INT(_arg_nr);
 106         struct expression *arg;
 107
 108         arg = get_argument_from_call_expr(expr->args, arg_nr);
 109         check_is_err_ptr(arg);
 110 }
 111
 112 static void match_condition(struct expression *expr)
 113 {
 114         if (expr->type == EXPR_ASSIGNMENT) {
 115                 match_condition(expr->right);
 116                 match_condition(expr->left);
 117         }
 118         if (!get_state_expr(my_id, expr))
 119                 return;
 120         /* If we know the variable is zero that means it's not an ERR_PTR */
 121         set_true_false_states_expr(my_id, expr, NULL, &checked);
 122 }
 123
 124 static void register_err_ptr_funcs(void)
 125 {
 126         struct token *token;
 127         const char *func;
 128
 129         token = get_tokens_file("kernel.returns_err_ptr");
 130         if (!token)
 131                 return;
 132         if (token_type(token) != TOKEN_STREAMBEGIN)
 133                 return;
 134         token = token->next;
 135         while (token_type(token) != TOKEN_STREAMEND) {
 136                 if (token_type(token) != TOKEN_IDENT)
 137                         return;
 138                 func = show_ident(token->ident);
 139                 add_function_assign_hook(func, &match_returns_err_ptr, NULL);
 140                 token = token->next;
 141         }
 142         clear_token_alloc();
 143 }
 144
 145 static void match_err_ptr_positive_const(const char *fn, struct expression *expr, void *unused)
 146 {
 147         struct expression *arg;
 148         sval_t sval;
 149
 150         arg = get_argument_from_call_expr(expr->args, 0);
 151
 152         if (!get_value(arg, &sval))
 153                 return;
 154         if (sval_is_positive(sval) && sval_cmp_val(sval, 0) != 0)
 155                 sm_msg("error: passing non negative %s to ERR_PTR", sval_to_str(sval));
 156 }
 157
 158 static void match_err_ptr(const char *fn, struct expression *expr, void *unused)
 159 {
 160         struct expression *arg;
 161         struct sm_state *sm;
 162         struct sm_state *tmp;
 163         sval_t tmp_min;
 164         sval_t tmp_max;
 165         sval_t min = sval_type_max(&llong_ctype);
 166         sval_t max = sval_type_min(&llong_ctype);
 167
 168         arg = get_argument_from_call_expr(expr->args, 0);
 169         sm = get_sm_state_expr(SMATCH_EXTRA, arg);
 170         if (!sm)
 171                 return;
 172         FOR_EACH_PTR(sm->possible, tmp) {
 173                 tmp_min = estate_min(tmp->state);
 174                 if (!sval_is_a_min(tmp_min) && sval_cmp(tmp_min, min) < 0)
 175                         min = tmp_min;
 176                 tmp_max = estate_max(tmp->state);
 177                 if (!sval_is_a_max(tmp_max) && sval_cmp(tmp_max, max) > 0)
 178                         max = tmp_max;
 179         } END_FOR_EACH_PTR(tmp);
 180         if (sval_is_negative(min) && sval_cmp_val(min, -4095) < 0)
 181                 sm_msg("error: %s too low for ERR_PTR", sval_to_str(min));
 182         if (sval_is_positive(max) && sval_cmp_val(max, 0) != 0)
 183                 sm_msg("error: passing non negative %s to ERR_PTR", sval_to_str(max));
 184 }
 185
 186 void check_err_ptr_deref(int id)
 187 {
 188         if (option_project != PROJ_KERNEL)
 189                 return;
 190
 191         my_id = id;
 192         return_implies_state("IS_ERR", 0, 0, &match_checked, NULL);
 193         return_implies_state("IS_ERR", 1, 1, &match_err, NULL);
 194         return_implies_state("IS_ERR_OR_NULL", 0, 0, &match_checked, NULL);
 195         return_implies_state("IS_ERR_OR_NULL", 1, 1, &match_err, NULL);
 196         return_implies_state("PTR_RET", 0, 0, &match_checked, NULL);
 197         return_implies_state("PTR_RET", -4096, -1, &match_err, NULL);
 198         register_err_ptr_funcs();
 199         add_hook(&match_dereferences, DEREF_HOOK);
 200         add_function_hook("ERR_PTR", &match_err_ptr_positive_const, NULL);
 201         add_function_hook("ERR_PTR", &match_err_ptr, NULL);
 202         add_hook(&match_condition, CONDITION_HOOK);
 203         add_modification_hook(my_id, &ok_to_use);
 204         add_function_hook("kfree", &match_kfree, INT_PTR(0));
 205         add_function_hook("brelse", &match_kfree, INT_PTR(0));
 206         add_function_hook("kmem_cache_free", &match_kfree, INT_PTR(1));
 207         add_function_hook("vfree", &match_kfree, INT_PTR(0));
 208
 209         err_ptr_rl = clone_rl_permanent(alloc_rl(err_ptr_min, err_ptr_max));
 210 }
 211