check_dev_queue_xmit.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  * According to an email on lkml you are not allowed to reuse the skb
  20  * passed to dev_queue_xmit()
  21  *
  22  */
  23
  24 #include "smatch.h"
  25 #include "smatch_slist.h"
  26
  27 static int my_id;
  28
  29 STATE(do_not_use);
  30
  31 static int valid_use(void)
  32 {
  33         struct expression *tmp;
  34         int i = 0;
  35         int dot_ops = 0;
  36
  37         FOR_EACH_PTR_REVERSE(big_expression_stack, tmp) {
  38                 if (!i++)
  39                         continue;
  40                 if (tmp->type == EXPR_PREOP && tmp->op == '(')
  41                         continue;
  42                 if (tmp->op == '.' && !dot_ops++)
  43                         continue;
  44 //              if (tmp->type == EXPR_POSTOP)
  45 //                      return 1;
  46                 if (tmp->type == EXPR_CALL && sym_name_is("kfree_skb", tmp->fn))
  47                         return 1;
  48                 return 0;
  49         } END_FOR_EACH_PTR_REVERSE(tmp);
  50         return 0;
  51 }
  52
  53 /* match symbol is expensive.  only turn it on after we match the xmit function */
  54 static int match_symbol_active;
  55 static void match_symbol(struct expression *expr)
  56 {
  57         struct sm_state *sm;
  58         char *name;
  59
  60         sm = get_sm_state_expr(my_id, expr);
  61         if (!sm || !slist_has_state(sm->possible, &do_not_use))
  62                 return;
  63         if (valid_use())
  64                 return;
  65         name = expr_to_var(expr);
  66         sm_error("'%s' was already used up by dev_queue_xmit()", name);
  67         free_string(name);
  68 }
  69
  70 static void match_kfree_skb(const char *fn, struct expression *expr, void *param)
  71 {
  72         struct expression *arg;
  73
  74         arg = get_argument_from_call_expr(expr->args, 0);
  75         if (!arg)
  76                 return;
  77         set_state_expr(my_id, arg, &undefined);
  78 }
  79
  80 static void match_xmit(const char *fn, struct expression *expr, void *param)
  81 {
  82         struct expression *arg;
  83
  84         arg = get_argument_from_call_expr(expr->args, PTR_INT(param));
  85         if (!arg)
  86                 return;
  87         set_state_expr(my_id, arg, &do_not_use);
  88         if (!match_symbol_active++) {
  89                 add_hook(&match_symbol, SYM_HOOK);
  90                 add_function_hook("kfree_skb", &match_kfree_skb, NULL);
  91         }
  92 }
  93
  94 static void register_funcs_from_file(void)
  95 {
  96         struct token *token;
  97         const char *func;
  98         int arg;
  99
 100         token = get_tokens_file("kernel.dev_queue_xmit");
 101         if (!token)
 102                 return;
 103         if (token_type(token) != TOKEN_STREAMBEGIN)
 104                 return;
 105         token = token->next;
 106         while (token_type(token) != TOKEN_STREAMEND) {
 107                 if (token_type(token) != TOKEN_IDENT)
 108                         return;
 109                 func = show_ident(token->ident);
 110                 token = token->next;
 111                 if (token_type(token) != TOKEN_NUMBER)
 112                         return;
 113                 arg = atoi(token->number);
 114                 add_function_hook(func, &match_xmit, INT_PTR(arg));
 115                 token = token->next;
 116         }
 117         clear_token_alloc();
 118 }
 119
 120 void check_dev_queue_xmit(int id)
 121 {
 122         if (option_project != PROJ_KERNEL)
 123                 return;
 124         my_id = id;
 125         add_modification_hook(my_id, &set_undefined);
 126         register_funcs_from_file();
 127 }