check_err_ptr_deref.c

   1 /*
   2  * sparse/check_err_ptr_deref.c
   3  *
   4  * Copyright (C) 2009 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "smatch.h"
  11 #include "smatch_slist.h"
  12 #include "smatch_extra.h"
  13
  14 static int my_id;
  15
  16 STATE(err_ptr);
  17 STATE(checked);
  18
  19 static void ok_to_use(const char *name, struct symbol *sym, struct expression *expr, void *unused)
  20 {
  21         set_state(my_id, name, sym, &checked);
  22 }
  23
  24 static void check_is_err_ptr(struct sm_state *sm)
  25 {
  26         if (!sm)
  27                 return;
  28
  29         if (slist_has_state(sm->possible, &err_ptr)) {
  30                 sm_msg("error: '%s' dereferencing possible ERR_PTR()",
  31                            sm->name);
  32                 set_state(my_id, sm->name, sm->sym, &checked);
  33         }
  34 }
  35
  36 static void match_returns_err_ptr(const char *fn, struct expression *expr,
  37                                 void *info)
  38 {
  39         set_state_expr(my_id, expr->left, &err_ptr);
  40 }
  41
  42
  43 static void match_checked(const char *fn, struct expression *call_expr,
  44                         struct expression *assign_expr, void *unused)
  45 {
  46         struct expression *arg;
  47
  48         arg = get_argument_from_call_expr(call_expr->args, 0);
  49         arg = strip_expr(arg);
  50         while (arg->type == EXPR_ASSIGNMENT)
  51                 arg = strip_expr(arg->left);
  52         set_state_expr(my_id, arg, &checked);
  53 }
  54
  55 static void match_err(const char *fn, struct expression *call_expr,
  56                         struct expression *assign_expr, void *unused)
  57 {
  58         struct expression *arg;
  59
  60         arg = get_argument_from_call_expr(call_expr->args, 0);
  61         arg = strip_expr(arg);
  62         while (arg->type == EXPR_ASSIGNMENT)
  63                 arg = strip_expr(arg->left);
  64         set_state_expr(my_id, arg, &err_ptr);
  65 }
  66
  67 static void match_dereferences(struct expression *expr)
  68 {
  69         struct sm_state *sm;
  70
  71         if (expr->type != EXPR_PREOP)
  72                 return;
  73         expr = strip_expr(expr->unop);
  74
  75         sm = get_sm_state_expr(my_id, expr);
  76         check_is_err_ptr(sm);
  77 }
  78
  79 static void match_condition(struct expression *expr)
  80 {
  81         if (expr->type == EXPR_ASSIGNMENT) {
  82                 match_condition(expr->right);
  83                 match_condition(expr->left);
  84         }
  85         if (!get_state_expr(my_id, expr))
  86                 return;
  87         /* If we know the variable is zero that means it's not an ERR_PTR */
  88         set_true_false_states_expr(my_id, expr, NULL, &checked);
  89 }
  90
  91 static void register_err_ptr_funcs(void)
  92 {
  93         struct token *token;
  94         const char *func;
  95
  96         token = get_tokens_file("kernel.returns_err_ptr");
  97         if (!token)
  98                 return;
  99         if (token_type(token) != TOKEN_STREAMBEGIN)
 100                 return;
 101         token = token->next;
 102         while (token_type(token) != TOKEN_STREAMEND) {
 103                 if (token_type(token) != TOKEN_IDENT)
 104                         return;
 105                 func = show_ident(token->ident);
 106                 add_function_assign_hook(func, &match_returns_err_ptr, NULL);
 107                 token = token->next;
 108         }
 109         clear_token_alloc();
 110 }
 111
 112 static void match_err_ptr(const char *fn, struct expression *expr, void *unused)
 113 {
 114         struct expression *arg;
 115         struct sm_state *sm;
 116         struct sm_state *tmp;
 117         long long tmp_min;
 118         long long tmp_max;
 119         long long min = whole_range.max;
 120         long long max = whole_range.min;
 121
 122         arg = get_argument_from_call_expr(expr->args, 0);
 123         sm = get_sm_state_expr(SMATCH_EXTRA, arg);
 124         if (!sm)
 125                 return;
 126         FOR_EACH_PTR(sm->possible, tmp) {
 127                 tmp_min = get_dinfo_min(get_dinfo(tmp->state));
 128                 if (tmp_min != whole_range.min && tmp_min < min)
 129                         min = tmp_min;
 130                 tmp_max = get_dinfo_max(get_dinfo(tmp->state));
 131                 if (tmp_max != whole_range.max && tmp_max > max)
 132                         max = tmp_max;
 133         } END_FOR_EACH_PTR(tmp);
 134         if (min < -4095)
 135                 sm_msg("error: %lld too low for ERR_PTR", min);
 136         if (max > 0)
 137                 sm_msg("error: passing non neg %lld to ERR_PTR", max);
 138 }
 139
 140 static void match_ptr_err(const char *fn, struct expression *expr, void *unused)
 141 {
 142         struct expression *arg;
 143         struct expression *right;
 144
 145         right = strip_expr(expr->right);
 146         arg = get_argument_from_call_expr(right->args, 0);
 147         if (get_state_expr(my_id, arg) == &err_ptr) {
 148                 set_extra_expr_mod(expr->left, alloc_extra_state_range(-4095, -1));
 149         }
 150 }
 151
 152 void check_err_ptr_deref(int id)
 153 {
 154         if (option_project != PROJ_KERNEL)
 155                 return;
 156
 157         my_id = id;
 158         return_implies_state("IS_ERR", 0, 0, &match_checked, NULL);
 159         return_implies_state("IS_ERR", 1, 1, &match_err, NULL);
 160         return_implies_state("IS_ERR_OR_NULL", 0, 0, &match_checked, NULL);
 161         return_implies_state("IS_ERR_OR_NULL", 1, 1, &match_err, NULL);
 162         return_implies_state("PTR_RET", 0, 0, &match_checked, NULL);
 163         return_implies_state("PTR_RET", -4096, -1, &match_err, NULL);
 164         register_err_ptr_funcs();
 165         add_hook(&match_dereferences, DEREF_HOOK);
 166         add_function_hook("ERR_PTR", &match_err_ptr, NULL);
 167         add_function_assign_hook("PTR_ERR", &match_ptr_err, NULL);
 168         add_hook(&match_condition, CONDITION_HOOK);
 169         set_default_modification_hook(my_id, ok_to_use);
 170 }
 171