check_return_efault.c

   1 /*
   2  * smatch/check_return_efault.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * This tries to find places which should probably return -EFAULT
  12  * but return the number of bytes to copy instead.
  13  */
  14
  15 #include "smatch.h"
  16 #include "smatch_slist.h"
  17 #include "smatch_extra.h"
  18
  19 static int my_id;
  20
  21 STATE(remaining);
  22 STATE(ok);
  23
  24 static void ok_to_use(struct sm_state *sm)
  25 {
  26         if (sm->state != &ok)
  27                 set_state(my_id, sm->name, sm->sym, &ok);
  28 }
  29
  30 static void match_copy(const char *fn, struct expression *expr, void *unused)
  31 {
  32         struct expression *call;
  33         struct expression *arg;
  34         long long max;
  35
  36         if (expr->op == SPECIAL_SUB_ASSIGN)
  37                 return;
  38         set_state_expr(my_id, expr->left, &remaining);
  39
  40         call = strip_expr(expr->right);
  41         if (call->type != EXPR_CALL)
  42                 return;
  43         arg = get_argument_from_call_expr(call->args, 2);
  44         if (!get_absolute_max(arg, &max))
  45                 max = whole_range.max;
  46         set_extra_expr_mod(expr->left, alloc_estate_range(0, max));
  47
  48 }
  49
  50 static void match_condition(struct expression *expr)
  51 {
  52         if (!get_state_expr(my_id, expr))
  53                 return;
  54         /* If the variable is zero that's ok */
  55         set_true_false_states_expr(my_id, expr, NULL, &ok);
  56 }
  57
  58 /*
  59  * This function is biased in favour of print out errors.
  60  * The heuristic to print is:
  61  *    If we have a potentially positive return from copy_to_user
  62  *    and there is a possibility that we return negative as well
  63  *    then complain.
  64  */
  65 static void match_return(struct expression *ret_value)
  66 {
  67         struct smatch_state *state;
  68         struct sm_state *sm;
  69         long long min;
  70
  71         sm = get_sm_state_expr(my_id, ret_value);
  72         if (!sm)
  73                 return;
  74         if (!slist_has_state(sm->possible, &remaining))
  75                 return;
  76         state = get_state_expr(SMATCH_EXTRA, ret_value);
  77         if (!state)
  78                 return;
  79         if (!get_absolute_min(ret_value, &min))
  80                 return;
  81         if (min == 0)
  82                 return;
  83         sm_msg("warn: maybe return -EFAULT instead of the bytes remaining?");
  84 }
  85
  86 void check_return_efault(int id)
  87 {
  88         if (option_project != PROJ_KERNEL)
  89                 return;
  90
  91         my_id = id;
  92         add_function_assign_hook_extra("copy_to_user", &match_copy, NULL);
  93         add_function_assign_hook_extra("__copy_to_user", &match_copy, NULL);
  94         add_function_assign_hook_extra("copy_from_user", &match_copy, NULL);
  95         add_function_assign_hook_extra("__copy_from_user", &match_copy, NULL);
  96         add_function_assign_hook_extra("clear_user", &match_copy, NULL);
  97         add_hook(&match_condition, CONDITION_HOOK);
  98         add_hook(&match_return, RETURN_HOOK);
  99         add_modification_hook(my_id, &ok_to_use);
 100 }