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![John Johansen](/assets/img/avatar_default.png)
The top 8 bits of the base field have never been used, in fact can't be used, by the current 'dfa16' format. However they will be used in the future as flags, so mask them off when using base as an index value. Note: the use of the top 8 bits, without masking is trapped by the verify checks that base entries are within the size bounds. Signed-off-by: John Johansen <john.johansen@canonical.com> Acked-by: Kees Cook <kees@ubuntu.com>
428 lines
11 KiB
C
428 lines
11 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 2009-2012 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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#define base_idx(X) ((X) & 0xffffff)
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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 kfree)
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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 = kvzalloc(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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if (base_idx(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_idx(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_idx(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_match - 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_match 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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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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while (*str) {
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pos = base_idx(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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while (*str) {
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pos = base_idx(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 - step one character to the next state in the dfa
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* @dfa: the dfa to tranverse (NOT NULL)
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* @state: the state to start in
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* @c: the input character to transition on
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*
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* aa_dfa_match will step through the dfa by one input character @c
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*
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* Returns: state reach after input @c
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*/
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unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
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const char c)
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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 pos;
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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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pos = base_idx(base[state]) + equiv[(u8) c];
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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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} else {
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/* default is direct to next state */
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pos = base_idx(base[state]) + (u8) c;
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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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return state;
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}
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