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 void ok_to_use(struct sm_state *sm, struct expression *mod_expr)
  28 {
  29         if (sm->state != &checked)
  30                 set_state(my_id, sm->name, sm->sym, &checked);
  31 }
  32
  33 static void check_is_err_ptr(struct sm_state *sm)
  34 {
  35         if (!sm)
  36                 return;
  37
  38         if (slist_has_state(sm->possible, &err_ptr)) {
  39                 sm_msg("error: '%s' dereferencing possible ERR_PTR()",
  40                            sm->name);
  41                 set_state(my_id, sm->name, sm->sym, &checked);
  42         }
  43 }
  44
  45 static void match_returns_err_ptr(const char *fn, struct expression *expr,
  46                                 void *info)
  47 {
  48         set_state_expr(my_id, expr->left, &err_ptr);
  49 }
  50
  51
  52 static void match_checked(const char *fn, struct expression *call_expr,
  53                         struct expression *assign_expr, void *unused)
  54 {
  55         struct expression *arg;
  56
  57         arg = get_argument_from_call_expr(call_expr->args, 0);
  58         arg = strip_expr(arg);
  59         while (arg->type == EXPR_ASSIGNMENT)
  60                 arg = strip_expr(arg->left);
  61         set_state_expr(my_id, arg, &checked);
  62 }
  63
  64 static void match_err(const char *fn, struct expression *call_expr,
  65                         struct expression *assign_expr, void *unused)
  66 {
  67         struct expression *arg;
  68
  69         arg = get_argument_from_call_expr(call_expr->args, 0);
  70         arg = strip_expr(arg);
  71         while (arg->type == EXPR_ASSIGNMENT)
  72                 arg = strip_expr(arg->left);
  73         set_state_expr(my_id, arg, &err_ptr);
  74 }
  75
  76 static void match_dereferences(struct expression *expr)
  77 {
  78         struct sm_state *sm;
  79
  80         if (expr->type != EXPR_PREOP)
  81                 return;
  82         expr = strip_expr(expr->unop);
  83
  84         sm = get_sm_state_expr(my_id, expr);
  85         check_is_err_ptr(sm);
  86 }
  87
  88 static void match_kfree(const char *fn, struct expression *expr, void *_arg_nr)
  89 {
  90         int arg_nr = PTR_INT(_arg_nr);
  91         struct expression *arg;
  92         struct sm_state *sm;
  93
  94         arg = get_argument_from_call_expr(expr->args, arg_nr);
  95
  96         sm = get_sm_state_expr(my_id, arg);
  97         check_is_err_ptr(sm);
  98 }
  99
 100 static void match_condition(struct expression *expr)
 101 {
 102         if (expr->type == EXPR_ASSIGNMENT) {
 103                 match_condition(expr->right);
 104                 match_condition(expr->left);
 105         }
 106         if (!get_state_expr(my_id, expr))
 107                 return;
 108         /* If we know the variable is zero that means it's not an ERR_PTR */
 109         set_true_false_states_expr(my_id, expr, NULL, &checked);
 110 }
 111
 112 static void register_err_ptr_funcs(void)
 113 {
 114         struct token *token;
 115         const char *func;
 116
 117         token = get_tokens_file("kernel.returns_err_ptr");
 118         if (!token)
 119                 return;
 120         if (token_type(token) != TOKEN_STREAMBEGIN)
 121                 return;
 122         token = token->next;
 123         while (token_type(token) != TOKEN_STREAMEND) {
 124                 if (token_type(token) != TOKEN_IDENT)
 125                         return;
 126                 func = show_ident(token->ident);
 127                 add_function_assign_hook(func, &match_returns_err_ptr, NULL);
 128                 token = token->next;
 129         }
 130         clear_token_alloc();
 131 }
 132
 133 static void match_err_ptr(const char *fn, struct expression *expr, void *unused)
 134 {
 135         struct expression *arg;
 136         struct sm_state *sm;
 137         struct sm_state *tmp;
 138         sval_t tmp_min;
 139         sval_t tmp_max;
 140         sval_t min = sval_type_max(&llong_ctype);
 141         sval_t max = sval_type_min(&llong_ctype);
 142
 143         arg = get_argument_from_call_expr(expr->args, 0);
 144         sm = get_sm_state_expr(SMATCH_EXTRA, arg);
 145         if (!sm)
 146                 return;
 147         FOR_EACH_PTR(sm->possible, tmp) {
 148                 tmp_min = estate_min(tmp->state);
 149                 if (!sval_is_a_min(tmp_min) && sval_cmp(tmp_min, min) < 0)
 150                         min = tmp_min;
 151                 tmp_max = estate_max(tmp->state);
 152                 if (!sval_is_a_max(tmp_max) && sval_cmp(tmp_max, max) > 0)
 153                         max = tmp_max;
 154         } END_FOR_EACH_PTR(tmp);
 155         if (sval_is_negative(min) && sval_cmp_val(min, -4095) < 0)
 156                 sm_msg("error: %s too low for ERR_PTR", sval_to_str(min));
 157         if (sval_is_positive(max) && sval_cmp_val(max, 0) != 0)
 158                 sm_msg("error: passing non neg %s to ERR_PTR", sval_to_str(max));
 159 }
 160
 161 void check_err_ptr_deref(int id)
 162 {
 163         if (option_project != PROJ_KERNEL)
 164                 return;
 165
 166         my_id = id;
 167         return_implies_state("IS_ERR", 0, 0, &match_checked, NULL);
 168         return_implies_state("IS_ERR", 1, 1, &match_err, NULL);
 169         return_implies_state("IS_ERR_OR_NULL", 0, 0, &match_checked, NULL);
 170         return_implies_state("IS_ERR_OR_NULL", 1, 1, &match_err, NULL);
 171         return_implies_state("PTR_RET", 0, 0, &match_checked, NULL);
 172         return_implies_state("PTR_RET", -4096, -1, &match_err, NULL);
 173         register_err_ptr_funcs();
 174         add_hook(&match_dereferences, DEREF_HOOK);
 175         add_function_hook("ERR_PTR", &match_err_ptr, NULL);
 176         add_hook(&match_condition, CONDITION_HOOK);
 177         add_modification_hook(my_id, &ok_to_use);
 178         add_function_hook("kfree", &match_kfree, INT_PTR(0));
 179         add_function_hook("brelse", &match_kfree, INT_PTR(0));
 180         add_function_hook("kmem_cache_free", &match_kfree, INT_PTR(1));
 181         add_function_hook("vfree", &match_kfree, INT_PTR(0));
 182 }
 183