check_snprintf.c

   1 /*
   2  * Copyright (C) 2010 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 static void match_snprintf(const char *fn, struct expression *expr, void *info)
  25 {
  26         struct expression *call;
  27         struct expression *arg;
  28         sval_t buflen;
  29
  30         call = strip_expr(expr->right);
  31         arg = get_argument_from_call_expr(call->args, 1);
  32         if (!get_fuzzy_max(arg, &buflen))
  33                 return;
  34         set_state_expr(my_id, expr->left, alloc_state_num(buflen.value));
  35 }
  36
  37 static int get_old_buflen(struct sm_state *sm)
  38 {
  39         struct sm_state *tmp;
  40         int ret = 0;
  41
  42         FOR_EACH_PTR(sm->possible, tmp) {
  43                 if (PTR_INT(tmp->state->data) > ret)
  44                         ret = PTR_INT(tmp->state->data);
  45         } END_FOR_EACH_PTR(tmp);
  46         return ret;
  47 }
  48
  49 static void match_call(struct expression *expr)
  50 {
  51         struct expression *arg;
  52         struct sm_state *sm;
  53         int old_buflen;
  54         sval_t max;
  55
  56         FOR_EACH_PTR(expr->args, arg) {
  57                 sm = get_sm_state_expr(my_id, arg);
  58                 if (!sm)
  59                         continue;
  60                 old_buflen = get_old_buflen(sm);
  61                 if (!old_buflen)
  62                         return;
  63                 if (get_absolute_max(arg, &max) && sval_cmp_val(max, old_buflen) > 0)
  64                         sm_warning("'%s' returned from snprintf() might be larger than %d",
  65                                 sm->name, old_buflen);
  66         } END_FOR_EACH_PTR(arg);
  67 }
  68
  69 void check_snprintf(int id)
  70 {
  71         if (option_project != PROJ_KERNEL)
  72                 return;
  73         if (!option_spammy)
  74                 return;
  75
  76         my_id = id;
  77         set_dynamic_states(my_id);
  78         add_hook(&match_call, FUNCTION_CALL_HOOK);
  79         add_function_assign_hook("snprintf", &match_snprintf, NULL);
  80         add_modification_hook(my_id, &set_undefined);
  81 }
  82