check_checking_for_null_instead_of_err_ptr.c

   1 /*
   2  * Copyright (C) 2017 Oracle.
   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
  26 static struct string_list *ignored_macros;
  27
  28 static int in_ignored_macro(struct position pos)
  29 {
  30         const char *macro;
  31         char *tmp;
  32
  33         macro = get_macro_name(pos);
  34         if (!macro)
  35                 return 0;
  36
  37         FOR_EACH_PTR(ignored_macros, tmp) {
  38                 if (!strcmp(tmp, macro))
  39                         return 1;
  40         } END_FOR_EACH_PTR(tmp);
  41         return 0;
  42 }
  43
  44 static void ok_to_use(struct sm_state *sm, struct expression *mod_expr)
  45 {
  46         set_state(my_id, sm->name, sm->sym, &undefined);
  47 }
  48
  49 static void match_returns_err_ptr(const char *fn, struct expression *expr,
  50                                 void *info)
  51 {
  52         set_state_expr(my_id, expr->left, &err_ptr);
  53 }
  54
  55 static void match_condition(struct expression *expr)
  56 {
  57         struct sm_state *sm;
  58         struct range_list *rl;
  59         sval_t zero = {
  60                 .type = NULL,
  61                 { .value = 0, }
  62         };
  63         char *name;
  64         struct range_list *err_rl;
  65
  66         while (expr->type == EXPR_ASSIGNMENT)
  67                 expr = strip_expr(expr->left);
  68
  69         if (!is_pointer(expr))
  70                 return;
  71
  72         sm = get_sm_state_expr(my_id, expr);
  73         if (!sm)
  74                 return;
  75         if (!slist_has_state(sm->possible, &err_ptr))
  76                 return;
  77         if (!get_implied_rl(expr, &rl))
  78                 return;
  79         zero.type = rl_type(rl);
  80         if (rl_has_sval(rl, zero))
  81                 return;
  82
  83         /*
  84          * At this point we already know that the condition is bogus because
  85          * it's non-NULL.  But let's do another filter to make sure it really is
  86          * a possible error pointer.
  87          *
  88          */
  89
  90         err_rl = alloc_rl(err_min, err_max);
  91         if (!possibly_true_rl(rl, SPECIAL_EQUAL, err_rl))
  92                 return;
  93
  94         if (in_ignored_macro(expr->pos))
  95                 return;
  96
  97         name = expr_to_str(expr);
  98         sm_msg("warn: '%s' is an error pointer or valid", name);
  99         free_string(name);
 100 }
 101
 102 static void match_condition2(struct expression *expr)
 103 {
 104         struct range_list *rl;
 105         struct data_range *drange;
 106         char *name;
 107
 108         if (!is_pointer(expr))
 109                 return;
 110         if (!get_implied_rl(expr, &rl))
 111                 return;
 112
 113         FOR_EACH_PTR(rl, drange) {
 114                 if (sval_cmp(drange->min, drange->max) != 0)
 115                         continue;
 116                 if (drange->min.value >= -4095 && drange->min.value < 0)
 117                         goto warn;
 118         } END_FOR_EACH_PTR(drange);
 119
 120         return;
 121
 122 warn:
 123         name = expr_to_str(expr);
 124         sm_warning("'%s' could be an error pointer", name);
 125         free_string(name);
 126 }
 127
 128 static void register_err_ptr_funcs(void)
 129 {
 130         struct token *token;
 131         const char *func;
 132
 133         token = get_tokens_file("kernel.returns_err_ptr");
 134         if (!token)
 135                 return;
 136         if (token_type(token) != TOKEN_STREAMBEGIN)
 137                 return;
 138         token = token->next;
 139         while (token_type(token) != TOKEN_STREAMEND) {
 140                 if (token_type(token) != TOKEN_IDENT)
 141                         return;
 142                 func = show_ident(token->ident);
 143                 add_function_assign_hook(func, &match_returns_err_ptr, NULL);
 144                 token = token->next;
 145         }
 146         clear_token_alloc();
 147 }
 148
 149 static void register_ignored_macros(void)
 150 {
 151         struct token *token;
 152         char *macro;
 153         char name[256];
 154
 155         snprintf(name, 256, "%s.ignore_bogus_null_checks", option_project_str);
 156
 157         token = get_tokens_file(name);
 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                 macro = alloc_string(show_ident(token->ident));
 167                 add_ptr_list(&ignored_macros, macro);
 168                 token = token->next;
 169         }
 170         clear_token_alloc();
 171 }
 172
 173 void check_checking_for_null_instead_of_err_ptr(int id)
 174 {
 175         if (option_project != PROJ_KERNEL)
 176                 return;
 177
 178         my_id = id;
 179         register_err_ptr_funcs();
 180         add_hook(&match_condition, CONDITION_HOOK);
 181         if (option_spammy)
 182                 add_hook(&match_condition2, CONDITION_HOOK);
 183         add_modification_hook(my_id, &ok_to_use);
 184         register_ignored_macros();
 185 }
 186