check_return_efault.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 /*
  19  * This tries to find places which should probably return -EFAULT
  20  * but return the number of bytes to copy instead.
  21  */
  22
  23 #include "smatch.h"
  24 #include "smatch_slist.h"
  25 #include "smatch_extra.h"
  26
  27 static int my_id;
  28
  29 STATE(remaining);
  30 STATE(ok);
  31
  32 static void ok_to_use(struct sm_state *sm, struct expression *mod_expr)
  33 {
  34         if (sm->state != &ok)
  35                 set_state(my_id, sm->name, sm->sym, &ok);
  36 }
  37
  38 static void match_copy(const char *fn, struct expression *expr, void *unused)
  39 {
  40         if (expr->op == SPECIAL_SUB_ASSIGN)
  41                 return;
  42         set_state_expr(my_id, expr->left, &remaining);
  43 }
  44
  45 static void match_condition(struct expression *expr)
  46 {
  47         if (!get_state_expr(my_id, expr))
  48                 return;
  49         /* If the variable is zero that's ok */
  50         set_true_false_states_expr(my_id, expr, NULL, &ok);
  51 }
  52
  53 /*
  54  * This function is biased in favour of print out errors.
  55  * The heuristic to print is:
  56  *    If we have a potentially positive return from copy_to_user
  57  *    and there is a possibility that we return negative as well
  58  *    then complain.
  59  */
  60 static void match_return(struct expression *ret_value)
  61 {
  62         struct smatch_state *state;
  63         struct sm_state *sm;
  64         sval_t min;
  65
  66         sm = get_sm_state_expr(my_id, ret_value);
  67         if (!sm)
  68                 return;
  69         if (!slist_has_state(sm->possible, &remaining))
  70                 return;
  71         state = get_state_expr(SMATCH_EXTRA, ret_value);
  72         if (!state)
  73                 return;
  74         if (!get_absolute_min(ret_value, &min))
  75                 return;
  76         if (min.value == 0)
  77                 return;
  78         sm_msg("warn: maybe return -EFAULT instead of the bytes remaining?");
  79 }
  80
  81 void check_return_efault(int id)
  82 {
  83         if (option_project != PROJ_KERNEL)
  84                 return;
  85
  86         my_id = id;
  87         add_function_assign_hook("copy_to_user", &match_copy, NULL);
  88         add_function_assign_hook("__copy_to_user", &match_copy, NULL);
  89         add_function_assign_hook("copy_from_user", &match_copy, NULL);
  90         add_function_assign_hook("__copy_from_user", &match_copy, NULL);
  91         add_function_assign_hook("clear_user", &match_copy, NULL);
  92         add_hook(&match_condition, CONDITION_HOOK);
  93         add_hook(&match_return, RETURN_HOOK);
  94         add_modification_hook(my_id, &ok_to_use);
  95 }