354 lines
8.9 KiB
C
354 lines
8.9 KiB
C
/*
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* AppArmor security module
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*
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* This file contains AppArmor dfa based regular expression matching engine
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*
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* Copyright (C) 1998-2008 Novell/SUSE
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* Copyright 2009-2010 Canonical Ltd.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/err.h>
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#include <linux/kref.h>
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#include "include/apparmor.h"
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#include "include/match.h"
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/**
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* unpack_table - unpack a dfa table (one of accept, default, base, next check)
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* @blob: data to unpack (NOT NULL)
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* @bsize: size of blob
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*
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* Returns: pointer to table else NULL on failure
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*
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* NOTE: must be freed by kvfree (not kmalloc)
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*/
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static struct table_header *unpack_table(char *blob, size_t bsize)
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{
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struct table_header *table = NULL;
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struct table_header th;
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size_t tsize;
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if (bsize < sizeof(struct table_header))
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goto out;
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/* loaded td_id's start at 1, subtract 1 now to avoid doing
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* it every time we use td_id as an index
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*/
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th.td_id = be16_to_cpu(*(u16 *) (blob)) - 1;
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th.td_flags = be16_to_cpu(*(u16 *) (blob + 2));
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th.td_lolen = be32_to_cpu(*(u32 *) (blob + 8));
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blob += sizeof(struct table_header);
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if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 ||
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th.td_flags == YYTD_DATA8))
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goto out;
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tsize = table_size(th.td_lolen, th.td_flags);
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if (bsize < tsize)
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goto out;
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table = kvmalloc(tsize);
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if (table) {
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*table = th;
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if (th.td_flags == YYTD_DATA8)
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UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
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u8, byte_to_byte);
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else if (th.td_flags == YYTD_DATA16)
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UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
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u16, be16_to_cpu);
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else if (th.td_flags == YYTD_DATA32)
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UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
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u32, be32_to_cpu);
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else
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goto fail;
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}
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out:
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/* if table was vmalloced make sure the page tables are synced
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* before it is used, as it goes live to all cpus.
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*/
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if (is_vmalloc_addr(table))
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vm_unmap_aliases();
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return table;
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fail:
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kvfree(table);
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return NULL;
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}
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/**
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* verify_dfa - verify that transitions and states in the tables are in bounds.
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* @dfa: dfa to test (NOT NULL)
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* @flags: flags controlling what type of accept table are acceptable
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*
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* Assumes dfa has gone through the first pass verification done by unpacking
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* NOTE: this does not valid accept table values
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*
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* Returns: %0 else error code on failure to verify
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*/
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static int verify_dfa(struct aa_dfa *dfa, int flags)
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{
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size_t i, state_count, trans_count;
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int error = -EPROTO;
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/* check that required tables exist */
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if (!(dfa->tables[YYTD_ID_DEF] &&
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dfa->tables[YYTD_ID_BASE] &&
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dfa->tables[YYTD_ID_NXT] && dfa->tables[YYTD_ID_CHK]))
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goto out;
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/* accept.size == default.size == base.size */
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state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
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if (ACCEPT1_FLAGS(flags)) {
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if (!dfa->tables[YYTD_ID_ACCEPT])
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goto out;
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if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen)
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goto out;
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}
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if (ACCEPT2_FLAGS(flags)) {
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if (!dfa->tables[YYTD_ID_ACCEPT2])
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goto out;
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if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen)
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goto out;
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}
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if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen)
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goto out;
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/* next.size == chk.size */
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trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
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if (trans_count != dfa->tables[YYTD_ID_CHK]->td_lolen)
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goto out;
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/* if equivalence classes then its table size must be 256 */
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if (dfa->tables[YYTD_ID_EC] &&
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dfa->tables[YYTD_ID_EC]->td_lolen != 256)
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goto out;
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if (flags & DFA_FLAG_VERIFY_STATES) {
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for (i = 0; i < state_count; i++) {
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if (DEFAULT_TABLE(dfa)[i] >= state_count)
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goto out;
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/* TODO: do check that DEF state recursion terminates */
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if (BASE_TABLE(dfa)[i] + 255 >= trans_count) {
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printk(KERN_ERR "AppArmor DFA next/check upper "
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"bounds error\n");
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goto out;
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}
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}
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for (i = 0; i < trans_count; i++) {
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if (NEXT_TABLE(dfa)[i] >= state_count)
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goto out;
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if (CHECK_TABLE(dfa)[i] >= state_count)
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goto out;
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}
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}
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error = 0;
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out:
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return error;
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}
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/**
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* dfa_free - free a dfa allocated by aa_dfa_unpack
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* @dfa: the dfa to free (MAYBE NULL)
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*
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* Requires: reference count to dfa == 0
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*/
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static void dfa_free(struct aa_dfa *dfa)
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{
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if (dfa) {
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int i;
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for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
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kvfree(dfa->tables[i]);
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dfa->tables[i] = NULL;
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}
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kfree(dfa);
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}
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}
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/**
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* aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
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* @kr: kref callback for freeing of a dfa (NOT NULL)
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*/
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void aa_dfa_free_kref(struct kref *kref)
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{
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struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
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dfa_free(dfa);
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}
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/**
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* aa_dfa_unpack - unpack the binary tables of a serialized dfa
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* @blob: aligned serialized stream of data to unpack (NOT NULL)
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* @size: size of data to unpack
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* @flags: flags controlling what type of accept tables are acceptable
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*
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* Unpack a dfa that has been serialized. To find information on the dfa
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* format look in Documentation/security/apparmor.txt
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* Assumes the dfa @blob stream has been aligned on a 8 byte boundary
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*
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* Returns: an unpacked dfa ready for matching or ERR_PTR on failure
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*/
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struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
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{
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int hsize;
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int error = -ENOMEM;
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char *data = blob;
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struct table_header *table = NULL;
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struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
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if (!dfa)
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goto fail;
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kref_init(&dfa->count);
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error = -EPROTO;
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/* get dfa table set header */
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if (size < sizeof(struct table_set_header))
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goto fail;
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if (ntohl(*(u32 *) data) != YYTH_MAGIC)
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goto fail;
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hsize = ntohl(*(u32 *) (data + 4));
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if (size < hsize)
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goto fail;
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dfa->flags = ntohs(*(u16 *) (data + 12));
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data += hsize;
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size -= hsize;
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while (size > 0) {
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table = unpack_table(data, size);
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if (!table)
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goto fail;
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switch (table->td_id) {
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case YYTD_ID_ACCEPT:
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if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
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goto fail;
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break;
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case YYTD_ID_ACCEPT2:
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if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
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goto fail;
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break;
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case YYTD_ID_BASE:
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if (table->td_flags != YYTD_DATA32)
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goto fail;
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break;
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case YYTD_ID_DEF:
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case YYTD_ID_NXT:
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case YYTD_ID_CHK:
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if (table->td_flags != YYTD_DATA16)
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goto fail;
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break;
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case YYTD_ID_EC:
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if (table->td_flags != YYTD_DATA8)
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goto fail;
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break;
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default:
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goto fail;
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}
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/* check for duplicate table entry */
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if (dfa->tables[table->td_id])
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goto fail;
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dfa->tables[table->td_id] = table;
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data += table_size(table->td_lolen, table->td_flags);
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size -= table_size(table->td_lolen, table->td_flags);
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table = NULL;
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}
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error = verify_dfa(dfa, flags);
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if (error)
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goto fail;
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return dfa;
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fail:
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kvfree(table);
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dfa_free(dfa);
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return ERR_PTR(error);
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}
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/**
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* aa_dfa_match_len - traverse @dfa to find state @str stops at
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* @dfa: the dfa to match @str against (NOT NULL)
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* @start: the state of the dfa to start matching in
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* @str: the string of bytes to match against the dfa (NOT NULL)
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* @len: length of the string of bytes to match
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*
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* aa_dfa_match_len will match @str against the dfa and return the state it
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* finished matching in. The final state can be used to look up the accepting
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* label, or as the start state of a continuing match.
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*
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* This function will happily match again the 0 byte and only finishes
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* when @len input is consumed.
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*
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* Returns: final state reached after input is consumed
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*/
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unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
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const char *str, int len)
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{
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u16 *def = DEFAULT_TABLE(dfa);
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u32 *base = BASE_TABLE(dfa);
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u16 *next = NEXT_TABLE(dfa);
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u16 *check = CHECK_TABLE(dfa);
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unsigned int state = start, pos;
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if (state == 0)
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return 0;
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/* current state is <state>, matching character *str */
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if (dfa->tables[YYTD_ID_EC]) {
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/* Equivalence class table defined */
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u8 *equiv = EQUIV_TABLE(dfa);
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/* default is direct to next state */
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for (; len; len--) {
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pos = base[state] + equiv[(u8) *str++];
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if (check[pos] == state)
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state = next[pos];
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else
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state = def[state];
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}
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} else {
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/* default is direct to next state */
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for (; len; len--) {
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pos = base[state] + (u8) *str++;
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if (check[pos] == state)
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state = next[pos];
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else
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state = def[state];
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}
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}
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return state;
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}
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/**
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* aa_dfa_next_state - traverse @dfa to find state @str stops at
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* @dfa: the dfa to match @str against (NOT NULL)
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* @start: the state of the dfa to start matching in
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* @str: the null terminated string of bytes to match against the dfa (NOT NULL)
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*
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* aa_dfa_next_state will match @str against the dfa and return the state it
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* finished matching in. The final state can be used to look up the accepting
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* label, or as the start state of a continuing match.
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*
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* Returns: final state reached after input is consumed
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*/
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unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
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const char *str)
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{
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return aa_dfa_match_len(dfa, start, str, strlen(str));
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}
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