security/apparmor/match.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * AppArmor security module
  *
  * This file contains AppArmor dfa based regular expression matching engine
  *
  * Copyright (C) 1998-2008 Novell/SUSE
  * Copyright 2009-2012 Canonical Ltd.
  */

 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/err.h>
 #include <linux/kref.h>

 #include "include/lib.h"
 #include "include/match.h"

 #define base_idx(X) ((X) & 0xffffff)

 static char nulldfa_src[] = {
 	#include "nulldfa.in"
 };
 struct aa_dfa *nulldfa;

 static char stacksplitdfa_src[] = {
 	#include "stacksplitdfa.in"
 };
 struct aa_dfa *stacksplitdfa;

 int __init aa_setup_dfa_engine(void)
 {
 	int error;

 	nulldfa = aa_dfa_unpack(nulldfa_src, sizeof(nulldfa_src),
 				TO_ACCEPT1_FLAG(YYTD_DATA32) |
 				TO_ACCEPT2_FLAG(YYTD_DATA32));
 	if (IS_ERR(nulldfa)) {
 		error = PTR_ERR(nulldfa);
 		nulldfa = NULL;
 		return error;
 	}

 	stacksplitdfa = aa_dfa_unpack(stacksplitdfa_src,
 				      sizeof(stacksplitdfa_src),
 				      TO_ACCEPT1_FLAG(YYTD_DATA32) |
 				      TO_ACCEPT2_FLAG(YYTD_DATA32));
 	if (IS_ERR(stacksplitdfa)) {
 		aa_put_dfa(nulldfa);
 		nulldfa = NULL;
 		error = PTR_ERR(stacksplitdfa);
 		stacksplitdfa = NULL;
 		return error;
 	}

 	return 0;
 }

 void __init aa_teardown_dfa_engine(void)
 {
 	aa_put_dfa(stacksplitdfa);
 	aa_put_dfa(nulldfa);
 }

 /**
  * unpack_table - unpack a dfa table (one of accept, default, base, next check)
  * @blob: data to unpack (NOT NULL)
  * @bsize: size of blob
  *
  * Returns: pointer to table else NULL on failure
  *
  * NOTE: must be freed by kvfree (not kfree)
  */
 static struct table_header *unpack_table(char *blob, size_t bsize)
 {
 	struct table_header *table = NULL;
 	struct table_header th;
 	size_t tsize;

 	if (bsize < sizeof(struct table_header))
 		goto out;

 	/* loaded td_id's start at 1, subtract 1 now to avoid doing
 	 * it every time we use td_id as an index
 	 */
 	th.td_id = be16_to_cpu(*(__be16 *) (blob)) - 1;
 	if (th.td_id > YYTD_ID_MAX)
 		goto out;
 	th.td_flags = be16_to_cpu(*(__be16 *) (blob + 2));
 	th.td_lolen = be32_to_cpu(*(__be32 *) (blob + 8));
 	blob += sizeof(struct table_header);

 	if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 ||
 	      th.td_flags == YYTD_DATA8))
 		goto out;

 	/* if we have a table it must have some entries */
 	if (th.td_lolen == 0)
 		goto out;
 	tsize = table_size(th.td_lolen, th.td_flags);
 	if (bsize < tsize)
 		goto out;

 	table = kvzalloc(tsize, GFP_KERNEL);
 	if (table) {
 		table->td_id = th.td_id;
 		table->td_flags = th.td_flags;
 		table->td_lolen = th.td_lolen;
 		if (th.td_flags == YYTD_DATA8)
 			UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
 				     u8, u8, byte_to_byte);
 		else if (th.td_flags == YYTD_DATA16)
 			UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
 				     u16, __be16, be16_to_cpu);
 		else if (th.td_flags == YYTD_DATA32)
 			UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
 				     u32, __be32, be32_to_cpu);
 		else
 			goto fail;
 		/* if table was vmalloced make sure the page tables are synced
 		 * before it is used, as it goes live to all cpus.
 		 */
 		if (is_vmalloc_addr(table))
 			vm_unmap_aliases();
 	}

 out:
 	return table;
 fail:
 	kvfree(table);
 	return NULL;
 }

 /**
  * verify_table_headers - verify that the tables headers are as expected
  * @tables - array of dfa tables to check (NOT NULL)
  * @flags: flags controlling what type of accept table are acceptable
  *
  * Assumes dfa has gone through the first pass verification done by unpacking
  * NOTE: this does not valid accept table values
  *
  * Returns: %0 else error code on failure to verify
  */
 static int verify_table_headers(struct table_header **tables, int flags)
 {
 	size_t state_count, trans_count;
 	int error = -EPROTO;

 	/* check that required tables exist */
 	if (!(tables[YYTD_ID_DEF] && tables[YYTD_ID_BASE] &&
 	      tables[YYTD_ID_NXT] && tables[YYTD_ID_CHK]))
 		goto out;

 	/* accept.size == default.size == base.size */
 	state_count = tables[YYTD_ID_BASE]->td_lolen;
 	if (ACCEPT1_FLAGS(flags)) {
 		if (!tables[YYTD_ID_ACCEPT])
 			goto out;
 		if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen)
 			goto out;
 	}
 	if (ACCEPT2_FLAGS(flags)) {
 		if (!tables[YYTD_ID_ACCEPT2])
 			goto out;
 		if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen)
 			goto out;
 	}
 	if (state_count != tables[YYTD_ID_DEF]->td_lolen)
 		goto out;

 	/* next.size == chk.size */
 	trans_count = tables[YYTD_ID_NXT]->td_lolen;
 	if (trans_count != tables[YYTD_ID_CHK]->td_lolen)
 		goto out;

 	/* if equivalence classes then its table size must be 256 */
 	if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256)
 		goto out;

 	error = 0;
 out:
 	return error;
 }

 /**
  * verify_dfa - verify that transitions and states in the tables are in bounds.
  * @dfa: dfa to test  (NOT NULL)
  *
  * Assumes dfa has gone through the first pass verification done by unpacking
  * NOTE: this does not valid accept table values
  *
  * Returns: %0 else error code on failure to verify
  */
 static int verify_dfa(struct aa_dfa *dfa)
 {
 	size_t i, state_count, trans_count;
 	int error = -EPROTO;

 	state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
 	trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
 	if (state_count == 0)
 		goto out;
 	for (i = 0; i < state_count; i++) {
 		if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) &&
 		    (DEFAULT_TABLE(dfa)[i] >= state_count))
 			goto out;
 		if (BASE_TABLE(dfa)[i] & MATCH_FLAGS_INVALID) {
 			pr_err("AppArmor DFA state with invalid match flags");
 			goto out;
 		}
 		if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE)) {
 			if (!(dfa->flags & YYTH_FLAG_DIFF_ENCODE)) {
 				pr_err("AppArmor DFA diff encoded transition state without header flag");
 				goto out;
 			}
 		}
 		if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_OOB_TRANSITION)) {
 			if (base_idx(BASE_TABLE(dfa)[i]) < dfa->max_oob) {
 				pr_err("AppArmor DFA out of bad transition out of range");
 				goto out;
 			}
 			if (!(dfa->flags & YYTH_FLAG_OOB_TRANS)) {
 				pr_err("AppArmor DFA out of bad transition state without header flag");
 				goto out;
 			}
 		}
 		if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
 			pr_err("AppArmor DFA next/check upper bounds error\n");
 			goto out;
 		}
 	}

 	for (i = 0; i < trans_count; i++) {
 		if (NEXT_TABLE(dfa)[i] >= state_count)
 			goto out;
 		if (CHECK_TABLE(dfa)[i] >= state_count)
 			goto out;
 	}

 	/* Now that all the other tables are verified, verify diffencoding */
 	for (i = 0; i < state_count; i++) {
 		size_t j, k;

 		for (j = i;
 		     (BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) &&
 		     !(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE);
 		     j = k) {
 			k = DEFAULT_TABLE(dfa)[j];
 			if (j == k)
 				goto out;
 			if (k < j)
 				break;		/* already verified */
 			BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE;
 		}
 	}
 	error = 0;

 out:
 	return error;
 }

 /**
  * dfa_free - free a dfa allocated by aa_dfa_unpack
  * @dfa: the dfa to free  (MAYBE NULL)
  *
  * Requires: reference count to dfa == 0
  */
 static void dfa_free(struct aa_dfa *dfa)
 {
 	if (dfa) {
 		int i;

 		for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
 			kvfree(dfa->tables[i]);
 			dfa->tables[i] = NULL;
 		}
 		kfree(dfa);
 	}
 }

 /**
  * aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
  * @kr: kref callback for freeing of a dfa  (NOT NULL)
  */
 void aa_dfa_free_kref(struct kref *kref)
 {
 	struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
 	dfa_free(dfa);
 }

 /**
  * aa_dfa_unpack - unpack the binary tables of a serialized dfa
  * @blob: aligned serialized stream of data to unpack  (NOT NULL)
  * @size: size of data to unpack
  * @flags: flags controlling what type of accept tables are acceptable
  *
  * Unpack a dfa that has been serialized.  To find information on the dfa
  * format look in Documentation/admin-guide/LSM/apparmor.rst
  * Assumes the dfa @blob stream has been aligned on a 8 byte boundary
  *
  * Returns: an unpacked dfa ready for matching or ERR_PTR on failure
  */
 struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
 {
 	int hsize;
 	int error = -ENOMEM;
 	char *data = blob;
 	struct table_header *table = NULL;
 	struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
 	if (!dfa)
 		goto fail;

 	kref_init(&dfa->count);

 	error = -EPROTO;

 	/* get dfa table set header */
 	if (size < sizeof(struct table_set_header))
 		goto fail;

 	if (ntohl(*(__be32 *) data) != YYTH_MAGIC)
 		goto fail;

 	hsize = ntohl(*(__be32 *) (data + 4));
 	if (size < hsize)
 		goto fail;

 	dfa->flags = ntohs(*(__be16 *) (data + 12));
 	if (dfa->flags & ~(YYTH_FLAGS))
 		goto fail;

 	/*
 	 * TODO: needed for dfa to support more than 1 oob
 	 * if (dfa->flags & YYTH_FLAGS_OOB_TRANS) {
 	 *	if (hsize < 16 + 4)
 	 *		goto fail;
 	 *	dfa->max_oob = ntol(*(__be32 *) (data + 16));
 	 *	if (dfa->max <= MAX_OOB_SUPPORTED) {
 	 *		pr_err("AppArmor DFA OOB greater than supported\n");
 	 *		goto fail;
 	 *	}
 	 * }
 	 */
 	dfa->max_oob = 1;

 	data += hsize;
 	size -= hsize;

 	while (size > 0) {
 		table = unpack_table(data, size);
 		if (!table)
 			goto fail;

 		switch (table->td_id) {
 		case YYTD_ID_ACCEPT:
 			if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
 				goto fail;
 			break;
 		case YYTD_ID_ACCEPT2:
 			if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
 				goto fail;
 			break;
 		case YYTD_ID_BASE:
 			if (table->td_flags != YYTD_DATA32)
 				goto fail;
 			break;
 		case YYTD_ID_DEF:
 		case YYTD_ID_NXT:
 		case YYTD_ID_CHK:
 			if (table->td_flags != YYTD_DATA16)
 				goto fail;
 			break;
 		case YYTD_ID_EC:
 			if (table->td_flags != YYTD_DATA8)
 				goto fail;
 			break;
 		default:
 			goto fail;
 		}
 		/* check for duplicate table entry */
 		if (dfa->tables[table->td_id])
 			goto fail;
 		dfa->tables[table->td_id] = table;
 		data += table_size(table->td_lolen, table->td_flags);
 		size -= table_size(table->td_lolen, table->td_flags);
 		table = NULL;
 	}
 	error = verify_table_headers(dfa->tables, flags);
 	if (error)
 		goto fail;

 	if (flags & DFA_FLAG_VERIFY_STATES) {
 		error = verify_dfa(dfa);
 		if (error)
 			goto fail;
 	}

 	return dfa;

 fail:
 	kvfree(table);
 	dfa_free(dfa);
 	return ERR_PTR(error);
 }

 #define match_char(state, def, base, next, check, C)	\
 do {							\
 	u32 b = (base)[(state)];			\
 	unsigned int pos = base_idx(b) + (C);		\
 	if ((check)[pos] != (state)) {			\
 		(state) = (def)[(state)];		\
 		if (b & MATCH_FLAG_DIFF_ENCODE)		\
 			continue;			\
 		break;					\
 	}						\
 	(state) = (next)[pos];				\
 	break;						\
 } while (1)

 /**
  * aa_dfa_match_len - traverse @dfa to find state @str stops at
  * @dfa: the dfa to match @str against  (NOT NULL)
  * @start: the state of the dfa to start matching in
  * @str: the string of bytes to match against the dfa  (NOT NULL)
  * @len: length of the string of bytes to match
  *
  * aa_dfa_match_len will match @str against the dfa and return the state it
  * finished matching in. The final state can be used to look up the accepting
  * label, or as the start state of a continuing match.
  *
  * This function will happily match again the 0 byte and only finishes
  * when @len input is consumed.
  *
  * Returns: final state reached after input is consumed
  */
 aa_state_t aa_dfa_match_len(struct aa_dfa *dfa, aa_state_t start,
 			    const char *str, int len)
 {
 	u16 *def = DEFAULT_TABLE(dfa);
 	u32 *base = BASE_TABLE(dfa);
 	u16 *next = NEXT_TABLE(dfa);
 	u16 *check = CHECK_TABLE(dfa);
 	aa_state_t state = start;

 	if (state == DFA_NOMATCH)
 		return DFA_NOMATCH;

 	/* current state is <state>, matching character *str */
 	if (dfa->tables[YYTD_ID_EC]) {
 		/* Equivalence class table defined */
 		u8 *equiv = EQUIV_TABLE(dfa);
 		for (; len; len--)
 			match_char(state, def, base, next, check,
 				   equiv[(u8) *str++]);
 	} else {
 		/* default is direct to next state */
 		for (; len; len--)
 			match_char(state, def, base, next, check, (u8) *str++);
 	}

 	return state;
 }

 /**
  * aa_dfa_match - traverse @dfa to find state @str stops at
  * @dfa: the dfa to match @str against  (NOT NULL)
  * @start: the state of the dfa to start matching in
  * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
  *
  * aa_dfa_match will match @str against the dfa and return the state it
  * finished matching in. The final state can be used to look up the accepting
  * label, or as the start state of a continuing match.
  *
  * Returns: final state reached after input is consumed
  */
 aa_state_t aa_dfa_match(struct aa_dfa *dfa, aa_state_t start, const char *str)
 {
 	u16 *def = DEFAULT_TABLE(dfa);
 	u32 *base = BASE_TABLE(dfa);
 	u16 *next = NEXT_TABLE(dfa);
 	u16 *check = CHECK_TABLE(dfa);
 	aa_state_t state = start;

 	if (state == DFA_NOMATCH)
 		return DFA_NOMATCH;

 	/* current state is <state>, matching character *str */
 	if (dfa->tables[YYTD_ID_EC]) {
 		/* Equivalence class table defined */
 		u8 *equiv = EQUIV_TABLE(dfa);
 		/* default is direct to next state */
 		while (*str)
 			match_char(state, def, base, next, check,
 				   equiv[(u8) *str++]);
 	} else {
 		/* default is direct to next state */
 		while (*str)
 			match_char(state, def, base, next, check, (u8) *str++);
 	}

 	return state;
 }

 /**
  * aa_dfa_next - step one character to the next state in the dfa
  * @dfa: the dfa to traverse (NOT NULL)
  * @state: the state to start in
  * @c: the input character to transition on
  *
  * aa_dfa_match will step through the dfa by one input character @c
  *
  * Returns: state reach after input @c
  */
 aa_state_t aa_dfa_next(struct aa_dfa *dfa, aa_state_t state, const char c)
 {
 	u16 *def = DEFAULT_TABLE(dfa);
 	u32 *base = BASE_TABLE(dfa);
 	u16 *next = NEXT_TABLE(dfa);
 	u16 *check = CHECK_TABLE(dfa);

 	/* current state is <state>, matching character *str */
 	if (dfa->tables[YYTD_ID_EC]) {
 		/* Equivalence class table defined */
 		u8 *equiv = EQUIV_TABLE(dfa);
 		match_char(state, def, base, next, check, equiv[(u8) c]);
 	} else
 		match_char(state, def, base, next, check, (u8) c);

 	return state;
 }

 aa_state_t aa_dfa_outofband_transition(struct aa_dfa *dfa, aa_state_t state)
 {
 	u16 *def = DEFAULT_TABLE(dfa);
 	u32 *base = BASE_TABLE(dfa);
 	u16 *next = NEXT_TABLE(dfa);
 	u16 *check = CHECK_TABLE(dfa);
 	u32 b = (base)[(state)];

 	if (!(b & MATCH_FLAG_OOB_TRANSITION))
 		return DFA_NOMATCH;

 	/* No Equivalence class remapping for outofband transitions */
 	match_char(state, def, base, next, check, -1);

 	return state;
 }

 /**
  * aa_dfa_match_until - traverse @dfa until accept state or end of input
  * @dfa: the dfa to match @str against  (NOT NULL)
  * @start: the state of the dfa to start matching in
  * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
  * @retpos: first character in str after match OR end of string
  *
  * aa_dfa_match will match @str against the dfa and return the state it
  * finished matching in. The final state can be used to look up the accepting
  * label, or as the start state of a continuing match.
  *
  * Returns: final state reached after input is consumed
  */
 aa_state_t aa_dfa_match_until(struct aa_dfa *dfa, aa_state_t start,
 				const char *str, const char **retpos)
 {
 	u16 *def = DEFAULT_TABLE(dfa);
 	u32 *base = BASE_TABLE(dfa);
 	u16 *next = NEXT_TABLE(dfa);
 	u16 *check = CHECK_TABLE(dfa);
 	u32 *accept = ACCEPT_TABLE(dfa);
 	aa_state_t state = start, pos;

 	if (state == DFA_NOMATCH)
 		return DFA_NOMATCH;

 	/* current state is <state>, matching character *str */
 	if (dfa->tables[YYTD_ID_EC]) {
 		/* Equivalence class table defined */
 		u8 *equiv = EQUIV_TABLE(dfa);
 		/* default is direct to next state */
 		while (*str) {
 			pos = base_idx(base[state]) + equiv[(u8) *str++];
 			if (check[pos] == state)
 				state = next[pos];
 			else
 				state = def[state];
 			if (accept[state])
 				break;
 		}
 	} else {
 		/* default is direct to next state */
 		while (*str) {
 			pos = base_idx(base[state]) + (u8) *str++;
 			if (check[pos] == state)
 				state = next[pos];
 			else
 				state = def[state];
 			if (accept[state])
 				break;
 		}
 	}

 	*retpos = str;
 	return state;
 }

 /**
  * aa_dfa_matchn_until - traverse @dfa until accept or @n bytes consumed
  * @dfa: the dfa to match @str against  (NOT NULL)
  * @start: the state of the dfa to start matching in
  * @str: the string of bytes to match against the dfa  (NOT NULL)
  * @n: length of the string of bytes to match
  * @retpos: first character in str after match OR str + n
  *
  * aa_dfa_match_len will match @str against the dfa and return the state it
  * finished matching in. The final state can be used to look up the accepting
  * label, or as the start state of a continuing match.
  *
  * This function will happily match again the 0 byte and only finishes
  * when @n input is consumed.
  *
  * Returns: final state reached after input is consumed
  */
 aa_state_t aa_dfa_matchn_until(struct aa_dfa *dfa, aa_state_t start,
 				 const char *str, int n, const char **retpos)
 {
 	u16 *def = DEFAULT_TABLE(dfa);
 	u32 *base = BASE_TABLE(dfa);
 	u16 *next = NEXT_TABLE(dfa);
 	u16 *check = CHECK_TABLE(dfa);
 	u32 *accept = ACCEPT_TABLE(dfa);
 	aa_state_t state = start, pos;

 	*retpos = NULL;
 	if (state == DFA_NOMATCH)
 		return DFA_NOMATCH;

 	/* current state is <state>, matching character *str */
 	if (dfa->tables[YYTD_ID_EC]) {
 		/* Equivalence class table defined */
 		u8 *equiv = EQUIV_TABLE(dfa);
 		/* default is direct to next state */
 		for (; n; n--) {
 			pos = base_idx(base[state]) + equiv[(u8) *str++];
 			if (check[pos] == state)
 				state = next[pos];
 			else
 				state = def[state];
 			if (accept[state])
 				break;
 		}
 	} else {
 		/* default is direct to next state */
 		for (; n; n--) {
 			pos = base_idx(base[state]) + (u8) *str++;
 			if (check[pos] == state)
 				state = next[pos];
 			else
 				state = def[state];
 			if (accept[state])
 				break;
 		}
 	}

 	*retpos = str;
 	return state;
 }

 #define inc_wb_pos(wb)						\
 do {								\
 	wb->pos = (wb->pos + 1) & (WB_HISTORY_SIZE - 1);		\
 	wb->len = (wb->len + 1) & (WB_HISTORY_SIZE - 1);		\
 } while (0)

 /* For DFAs that don't support extended tagging of states */
 static bool is_loop(struct match_workbuf *wb, aa_state_t state,
 		    unsigned int *adjust)
 {
 	aa_state_t pos = wb->pos;
 	aa_state_t i;

 	if (wb->history[pos] < state)
 		return false;

 	for (i = 0; i <= wb->len; i++) {
 		if (wb->history[pos] == state) {
 			*adjust = i;
 			return true;
 		}
 		if (pos == 0)
 			pos = WB_HISTORY_SIZE;
 		pos--;
 	}

 	*adjust = i;
 	return true;
 }

 static aa_state_t leftmatch_fb(struct aa_dfa *dfa, aa_state_t start,
 				 const char *str, struct match_workbuf *wb,
 				 unsigned int *count)
 {
 	u16 *def = DEFAULT_TABLE(dfa);
 	u32 *base = BASE_TABLE(dfa);
 	u16 *next = NEXT_TABLE(dfa);
 	u16 *check = CHECK_TABLE(dfa);
 	aa_state_t state = start, pos;

 	AA_BUG(!dfa);
 	AA_BUG(!str);
 	AA_BUG(!wb);
 	AA_BUG(!count);

 	*count = 0;
 	if (state == DFA_NOMATCH)
 		return DFA_NOMATCH;

 	/* current state is <state>, matching character *str */
 	if (dfa->tables[YYTD_ID_EC]) {
 		/* Equivalence class table defined */
 		u8 *equiv = EQUIV_TABLE(dfa);
 		/* default is direct to next state */
 		while (*str) {
 			unsigned int adjust;

 			wb->history[wb->pos] = state;
 			pos = base_idx(base[state]) + equiv[(u8) *str++];
 			if (check[pos] == state)
 				state = next[pos];
 			else
 				state = def[state];
 			if (is_loop(wb, state, &adjust)) {
 				state = aa_dfa_match(dfa, state, str);
 				*count -= adjust;
 				goto out;
 			}
 			inc_wb_pos(wb);
 			(*count)++;
 		}
 	} else {
 		/* default is direct to next state */
 		while (*str) {
 			unsigned int adjust;

 			wb->history[wb->pos] = state;
 			pos = base_idx(base[state]) + (u8) *str++;
 			if (check[pos] == state)
 				state = next[pos];
 			else
 				state = def[state];
 			if (is_loop(wb, state, &adjust)) {
 				state = aa_dfa_match(dfa, state, str);
 				*count -= adjust;
 				goto out;
 			}
 			inc_wb_pos(wb);
 			(*count)++;
 		}
 	}

 out:
 	if (!state)
 		*count = 0;
 	return state;
 }

 /**
  * aa_dfa_leftmatch - traverse @dfa to find state @str stops at
  * @dfa: the dfa to match @str against  (NOT NULL)
  * @start: the state of the dfa to start matching in
  * @str: the null terminated string of bytes to match against the dfa (NOT NULL)
  * @count: current count of longest left.
  *
  * aa_dfa_match will match @str against the dfa and return the state it
  * finished matching in. The final state can be used to look up the accepting
  * label, or as the start state of a continuing match.
  *
  * Returns: final state reached after input is consumed
  */
 aa_state_t aa_dfa_leftmatch(struct aa_dfa *dfa, aa_state_t start,
 			    const char *str, unsigned int *count)
 {
 	DEFINE_MATCH_WB(wb);

 	/* TODO: match for extended state dfas */

 	return leftmatch_fb(dfa, start, str, &wb, count);
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* AppArmor security module
	*
	* This file contains AppArmor dfa based regular expression matching engine
	*
	* Copyright (C) 1998-2008 Novell/SUSE
	* Copyright 2009-2012 Canonical Ltd.
	*/

	#include <linux/errno.h>
	#include <linux/kernel.h>
	#include <linux/mm.h>
	#include <linux/slab.h>
	#include <linux/vmalloc.h>
	#include <linux/err.h>
	#include <linux/kref.h>

	#include "include/lib.h"
	#include "include/match.h"

	#define base_idx(X) ((X) & 0xffffff)

	static char nulldfa_src[] = {
	#include "nulldfa.in"
	};
	struct aa_dfa *nulldfa;

	static char stacksplitdfa_src[] = {
	#include "stacksplitdfa.in"
	};
	struct aa_dfa *stacksplitdfa;

	int __init aa_setup_dfa_engine(void)
	{
	int error;

	nulldfa = aa_dfa_unpack(nulldfa_src, sizeof(nulldfa_src),
	TO_ACCEPT1_FLAG(YYTD_DATA32) \|
	TO_ACCEPT2_FLAG(YYTD_DATA32));
	if (IS_ERR(nulldfa)) {
	error = PTR_ERR(nulldfa);
	nulldfa = NULL;
	return error;
	}

	stacksplitdfa = aa_dfa_unpack(stacksplitdfa_src,
	sizeof(stacksplitdfa_src),
	TO_ACCEPT1_FLAG(YYTD_DATA32) \|
	TO_ACCEPT2_FLAG(YYTD_DATA32));
	if (IS_ERR(stacksplitdfa)) {
	aa_put_dfa(nulldfa);
	nulldfa = NULL;
	error = PTR_ERR(stacksplitdfa);
	stacksplitdfa = NULL;
	return error;
	}

	return 0;
	}

	void __init aa_teardown_dfa_engine(void)
	{
	aa_put_dfa(stacksplitdfa);
	aa_put_dfa(nulldfa);
	}

	/**
	* unpack_table - unpack a dfa table (one of accept, default, base, next check)
	* @blob: data to unpack (NOT NULL)
	* @bsize: size of blob
	*
	* Returns: pointer to table else NULL on failure
	*
	* NOTE: must be freed by kvfree (not kfree)
	*/
	static struct table_header unpack_table(char blob, size_t bsize)
	{
	struct table_header *table = NULL;
	struct table_header th;
	size_t tsize;

	if (bsize < sizeof(struct table_header))
	goto out;

	/* loaded td_id's start at 1, subtract 1 now to avoid doing
	* it every time we use td_id as an index
	*/
	th.td_id = be16_to_cpu((__be16 ) (blob)) - 1;
	if (th.td_id > YYTD_ID_MAX)
	goto out;
	th.td_flags = be16_to_cpu((__be16 ) (blob + 2));
	th.td_lolen = be32_to_cpu((__be32 ) (blob + 8));
	blob += sizeof(struct table_header);

	if (!(th.td_flags == YYTD_DATA16 \|\| th.td_flags == YYTD_DATA32 \|\|
	th.td_flags == YYTD_DATA8))
	goto out;

	/* if we have a table it must have some entries */
	if (th.td_lolen == 0)
	goto out;
	tsize = table_size(th.td_lolen, th.td_flags);
	if (bsize < tsize)
	goto out;

	table = kvzalloc(tsize, GFP_KERNEL);
	if (table) {
	table->td_id = th.td_id;
	table->td_flags = th.td_flags;
	table->td_lolen = th.td_lolen;
	if (th.td_flags == YYTD_DATA8)
	UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
	u8, u8, byte_to_byte);
	else if (th.td_flags == YYTD_DATA16)
	UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
	u16, __be16, be16_to_cpu);
	else if (th.td_flags == YYTD_DATA32)
	UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
	u32, __be32, be32_to_cpu);
	else
	goto fail;
	/* if table was vmalloced make sure the page tables are synced
	* before it is used, as it goes live to all cpus.
	*/
	if (is_vmalloc_addr(table))
	vm_unmap_aliases();
	}

	out:
	return table;
	fail:
	kvfree(table);
	return NULL;
	}

	/**
	* verify_table_headers - verify that the tables headers are as expected
	* @tables - array of dfa tables to check (NOT NULL)
	* @flags: flags controlling what type of accept table are acceptable
	*
	* Assumes dfa has gone through the first pass verification done by unpacking
	* NOTE: this does not valid accept table values
	*
	* Returns: %0 else error code on failure to verify
	*/
	static int verify_table_headers(struct table_header **tables, int flags)
	{
	size_t state_count, trans_count;
	int error = -EPROTO;

	/* check that required tables exist */
	if (!(tables[YYTD_ID_DEF] && tables[YYTD_ID_BASE] &&
	tables[YYTD_ID_NXT] && tables[YYTD_ID_CHK]))
	goto out;

	/* accept.size == default.size == base.size */
	state_count = tables[YYTD_ID_BASE]->td_lolen;
	if (ACCEPT1_FLAGS(flags)) {
	if (!tables[YYTD_ID_ACCEPT])
	goto out;
	if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen)
	goto out;
	}
	if (ACCEPT2_FLAGS(flags)) {
	if (!tables[YYTD_ID_ACCEPT2])
	goto out;
	if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen)
	goto out;
	}
	if (state_count != tables[YYTD_ID_DEF]->td_lolen)
	goto out;

	/* next.size == chk.size */
	trans_count = tables[YYTD_ID_NXT]->td_lolen;
	if (trans_count != tables[YYTD_ID_CHK]->td_lolen)
	goto out;

	/* if equivalence classes then its table size must be 256 */
	if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256)
	goto out;

	error = 0;
	out:
	return error;
	}

	/**
	* verify_dfa - verify that transitions and states in the tables are in bounds.
	* @dfa: dfa to test (NOT NULL)
	*
	* Assumes dfa has gone through the first pass verification done by unpacking
	* NOTE: this does not valid accept table values
	*
	* Returns: %0 else error code on failure to verify
	*/
	static int verify_dfa(struct aa_dfa *dfa)
	{
	size_t i, state_count, trans_count;
	int error = -EPROTO;

	state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
	trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;
	if (state_count == 0)
	goto out;
	for (i = 0; i < state_count; i++) {
	if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) &&
	(DEFAULT_TABLE(dfa)[i] >= state_count))
	goto out;
	if (BASE_TABLE(dfa)[i] & MATCH_FLAGS_INVALID) {
	pr_err("AppArmor DFA state with invalid match flags");
	goto out;
	}
	if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE)) {
	if (!(dfa->flags & YYTH_FLAG_DIFF_ENCODE)) {
	pr_err("AppArmor DFA diff encoded transition state without header flag");
	goto out;
	}
	}
	if ((BASE_TABLE(dfa)[i] & MATCH_FLAG_OOB_TRANSITION)) {
	if (base_idx(BASE_TABLE(dfa)[i]) < dfa->max_oob) {
	pr_err("AppArmor DFA out of bad transition out of range");
	goto out;
	}
	if (!(dfa->flags & YYTH_FLAG_OOB_TRANS)) {
	pr_err("AppArmor DFA out of bad transition state without header flag");
	goto out;
	}
	}
	if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
	pr_err("AppArmor DFA next/check upper bounds error\n");
	goto out;
	}
	}

	for (i = 0; i < trans_count; i++) {
	if (NEXT_TABLE(dfa)[i] >= state_count)
	goto out;
	if (CHECK_TABLE(dfa)[i] >= state_count)
	goto out;
	}

	/* Now that all the other tables are verified, verify diffencoding */
	for (i = 0; i < state_count; i++) {
	size_t j, k;

	for (j = i;
	(BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) &&
	!(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE);
	j = k) {
	k = DEFAULT_TABLE(dfa)[j];
	if (j == k)
	goto out;
	if (k < j)
	break; /* already verified */
	BASE_TABLE(dfa)[j] \|= MARK_DIFF_ENCODE;
	}
	}
	error = 0;

	out:
	return error;
	}

	/**
	* dfa_free - free a dfa allocated by aa_dfa_unpack
	* @dfa: the dfa to free (MAYBE NULL)
	*
	* Requires: reference count to dfa == 0
	*/
	static void dfa_free(struct aa_dfa *dfa)
	{
	if (dfa) {
	int i;

	for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
	kvfree(dfa->tables[i]);
	dfa->tables[i] = NULL;
	}
	kfree(dfa);
	}
	}

	/**
	* aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
	* @kr: kref callback for freeing of a dfa (NOT NULL)
	*/
	void aa_dfa_free_kref(struct kref *kref)
	{
	struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
	dfa_free(dfa);
	}

	/**
	* aa_dfa_unpack - unpack the binary tables of a serialized dfa
	* @blob: aligned serialized stream of data to unpack (NOT NULL)
	* @size: size of data to unpack
	* @flags: flags controlling what type of accept tables are acceptable
	*
	* Unpack a dfa that has been serialized. To find information on the dfa
	* format look in Documentation/admin-guide/LSM/apparmor.rst
	* Assumes the dfa @blob stream has been aligned on a 8 byte boundary
	*
	* Returns: an unpacked dfa ready for matching or ERR_PTR on failure
	*/
	struct aa_dfa aa_dfa_unpack(void blob, size_t size, int flags)
	{
	int hsize;
	int error = -ENOMEM;
	char *data = blob;
	struct table_header *table = NULL;
	struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
	if (!dfa)
	goto fail;

	kref_init(&dfa->count);

	error = -EPROTO;

	/* get dfa table set header */
	if (size < sizeof(struct table_set_header))
	goto fail;

	if (ntohl((__be32 ) data) != YYTH_MAGIC)
	goto fail;

	hsize = ntohl((__be32 ) (data + 4));
	if (size < hsize)
	goto fail;

	dfa->flags = ntohs((__be16 ) (data + 12));
	if (dfa->flags & ~(YYTH_FLAGS))
	goto fail;

	/*
	* TODO: needed for dfa to support more than 1 oob
	* if (dfa->flags & YYTH_FLAGS_OOB_TRANS) {
	* if (hsize < 16 + 4)
	* goto fail;
	* dfa->max_oob = ntol((__be32 ) (data + 16));
	* if (dfa->max <= MAX_OOB_SUPPORTED) {
	* pr_err("AppArmor DFA OOB greater than supported\n");
	* goto fail;
	* }
	* }
	*/
	dfa->max_oob = 1;

	data += hsize;
	size -= hsize;

	while (size > 0) {
	table = unpack_table(data, size);
	if (!table)
	goto fail;

	switch (table->td_id) {
	case YYTD_ID_ACCEPT:
	if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
	goto fail;
	break;
	case YYTD_ID_ACCEPT2:
	if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
	goto fail;
	break;
	case YYTD_ID_BASE:
	if (table->td_flags != YYTD_DATA32)
	goto fail;
	break;
	case YYTD_ID_DEF:
	case YYTD_ID_NXT:
	case YYTD_ID_CHK:
	if (table->td_flags != YYTD_DATA16)
	goto fail;
	break;
	case YYTD_ID_EC:
	if (table->td_flags != YYTD_DATA8)
	goto fail;
	break;
	default:
	goto fail;
	}
	/* check for duplicate table entry */
	if (dfa->tables[table->td_id])
	goto fail;
	dfa->tables[table->td_id] = table;
	data += table_size(table->td_lolen, table->td_flags);
	size -= table_size(table->td_lolen, table->td_flags);
	table = NULL;
	}
	error = verify_table_headers(dfa->tables, flags);
	if (error)
	goto fail;

	if (flags & DFA_FLAG_VERIFY_STATES) {
	error = verify_dfa(dfa);
	if (error)
	goto fail;
	}

	return dfa;

	fail:
	kvfree(table);
	dfa_free(dfa);
	return ERR_PTR(error);
	}

	#define match_char(state, def, base, next, check, C) \
	do { \
	u32 b = (base)[(state)]; \
	unsigned int pos = base_idx(b) + (C); \
	if ((check)[pos] != (state)) { \
	(state) = (def)[(state)]; \
	if (b & MATCH_FLAG_DIFF_ENCODE) \
	continue; \
	break; \
	} \
	(state) = (next)[pos]; \
	break; \
	} while (1)

	/**
	* aa_dfa_match_len - traverse @dfa to find state @str stops at
	* @dfa: the dfa to match @str against (NOT NULL)
	* @start: the state of the dfa to start matching in
	* @str: the string of bytes to match against the dfa (NOT NULL)
	* @len: length of the string of bytes to match
	*
	* aa_dfa_match_len will match @str against the dfa and return the state it
	* finished matching in. The final state can be used to look up the accepting
	* label, or as the start state of a continuing match.
	*
	* This function will happily match again the 0 byte and only finishes
	* when @len input is consumed.
	*
	* Returns: final state reached after input is consumed
	*/
	aa_state_t aa_dfa_match_len(struct aa_dfa *dfa, aa_state_t start,
	const char *str, int len)
	{
	u16 *def = DEFAULT_TABLE(dfa);
	u32 *base = BASE_TABLE(dfa);
	u16 *next = NEXT_TABLE(dfa);
	u16 *check = CHECK_TABLE(dfa);
	aa_state_t state = start;

	if (state == DFA_NOMATCH)
	return DFA_NOMATCH;

	/* current state is <state>, matching character str /
	if (dfa->tables[YYTD_ID_EC]) {
	/* Equivalence class table defined */
	u8 *equiv = EQUIV_TABLE(dfa);
	for (; len; len--)
	match_char(state, def, base, next, check,
	equiv[(u8) *str++]);
	} else {
	/* default is direct to next state */
	for (; len; len--)
	match_char(state, def, base, next, check, (u8) *str++);
	}

	return state;
	}

	/**
	* aa_dfa_match - traverse @dfa to find state @str stops at
	* @dfa: the dfa to match @str against (NOT NULL)
	* @start: the state of the dfa to start matching in
	* @str: the null terminated string of bytes to match against the dfa (NOT NULL)
	*
	* aa_dfa_match will match @str against the dfa and return the state it
	* finished matching in. The final state can be used to look up the accepting
	* label, or as the start state of a continuing match.
	*
	* Returns: final state reached after input is consumed
	*/
	aa_state_t aa_dfa_match(struct aa_dfa dfa, aa_state_t start, const char str)
	{
	u16 *def = DEFAULT_TABLE(dfa);
	u32 *base = BASE_TABLE(dfa);
	u16 *next = NEXT_TABLE(dfa);
	u16 *check = CHECK_TABLE(dfa);
	aa_state_t state = start;

	if (state == DFA_NOMATCH)
	return DFA_NOMATCH;

	/* current state is <state>, matching character str /
	if (dfa->tables[YYTD_ID_EC]) {
	/* Equivalence class table defined */
	u8 *equiv = EQUIV_TABLE(dfa);
	/* default is direct to next state */
	while (*str)
	match_char(state, def, base, next, check,
	equiv[(u8) *str++]);
	} else {
	/* default is direct to next state */
	while (*str)
	match_char(state, def, base, next, check, (u8) *str++);
	}

	return state;
	}

	/**
	* aa_dfa_next - step one character to the next state in the dfa
	* @dfa: the dfa to traverse (NOT NULL)
	* @state: the state to start in
	* @c: the input character to transition on
	*
	* aa_dfa_match will step through the dfa by one input character @c
	*
	* Returns: state reach after input @c
	*/
	aa_state_t aa_dfa_next(struct aa_dfa *dfa, aa_state_t state, const char c)
	{
	u16 *def = DEFAULT_TABLE(dfa);
	u32 *base = BASE_TABLE(dfa);
	u16 *next = NEXT_TABLE(dfa);
	u16 *check = CHECK_TABLE(dfa);

	/* current state is <state>, matching character str /
	if (dfa->tables[YYTD_ID_EC]) {
	/* Equivalence class table defined */
	u8 *equiv = EQUIV_TABLE(dfa);
	match_char(state, def, base, next, check, equiv[(u8) c]);
	} else
	match_char(state, def, base, next, check, (u8) c);

	return state;
	}

	aa_state_t aa_dfa_outofband_transition(struct aa_dfa *dfa, aa_state_t state)
	{
	u16 *def = DEFAULT_TABLE(dfa);
	u32 *base = BASE_TABLE(dfa);
	u16 *next = NEXT_TABLE(dfa);
	u16 *check = CHECK_TABLE(dfa);
	u32 b = (base)[(state)];

	if (!(b & MATCH_FLAG_OOB_TRANSITION))
	return DFA_NOMATCH;

	/* No Equivalence class remapping for outofband transitions */
	match_char(state, def, base, next, check, -1);

	return state;
	}

	/**
	* aa_dfa_match_until - traverse @dfa until accept state or end of input
	* @dfa: the dfa to match @str against (NOT NULL)
	* @start: the state of the dfa to start matching in
	* @str: the null terminated string of bytes to match against the dfa (NOT NULL)
	* @retpos: first character in str after match OR end of string
	*
	* aa_dfa_match will match @str against the dfa and return the state it
	* finished matching in. The final state can be used to look up the accepting
	* label, or as the start state of a continuing match.
	*
	* Returns: final state reached after input is consumed
	*/
	aa_state_t aa_dfa_match_until(struct aa_dfa *dfa, aa_state_t start,
	const char str, const char *retpos)
	{
	u16 *def = DEFAULT_TABLE(dfa);
	u32 *base = BASE_TABLE(dfa);
	u16 *next = NEXT_TABLE(dfa);
	u16 *check = CHECK_TABLE(dfa);
	u32 *accept = ACCEPT_TABLE(dfa);
	aa_state_t state = start, pos;

	if (state == DFA_NOMATCH)
	return DFA_NOMATCH;

	/* current state is <state>, matching character str /
	if (dfa->tables[YYTD_ID_EC]) {
	/* Equivalence class table defined */
	u8 *equiv = EQUIV_TABLE(dfa);
	/* default is direct to next state */
	while (*str) {
	pos = base_idx(base[state]) + equiv[(u8) *str++];
	if (check[pos] == state)
	state = next[pos];
	else
	state = def[state];
	if (accept[state])
	break;
	}
	} else {
	/* default is direct to next state */
	while (*str) {
	pos = base_idx(base[state]) + (u8) *str++;
	if (check[pos] == state)
	state = next[pos];
	else
	state = def[state];
	if (accept[state])
	break;
	}
	}

	*retpos = str;
	return state;
	}

	/**
	* aa_dfa_matchn_until - traverse @dfa until accept or @n bytes consumed
	* @dfa: the dfa to match @str against (NOT NULL)
	* @start: the state of the dfa to start matching in
	* @str: the string of bytes to match against the dfa (NOT NULL)
	* @n: length of the string of bytes to match
	* @retpos: first character in str after match OR str + n
	*
	* aa_dfa_match_len will match @str against the dfa and return the state it
	* finished matching in. The final state can be used to look up the accepting
	* label, or as the start state of a continuing match.
	*
	* This function will happily match again the 0 byte and only finishes
	* when @n input is consumed.
	*
	* Returns: final state reached after input is consumed
	*/
	aa_state_t aa_dfa_matchn_until(struct aa_dfa *dfa, aa_state_t start,
	const char str, int n, const char *retpos)
	{
	u16 *def = DEFAULT_TABLE(dfa);
	u32 *base = BASE_TABLE(dfa);
	u16 *next = NEXT_TABLE(dfa);
	u16 *check = CHECK_TABLE(dfa);
	u32 *accept = ACCEPT_TABLE(dfa);
	aa_state_t state = start, pos;

	*retpos = NULL;
	if (state == DFA_NOMATCH)
	return DFA_NOMATCH;

	/* current state is <state>, matching character str /
	if (dfa->tables[YYTD_ID_EC]) {
	/* Equivalence class table defined */
	u8 *equiv = EQUIV_TABLE(dfa);
	/* default is direct to next state */
	for (; n; n--) {
	pos = base_idx(base[state]) + equiv[(u8) *str++];
	if (check[pos] == state)
	state = next[pos];
	else
	state = def[state];
	if (accept[state])
	break;
	}
	} else {
	/* default is direct to next state */
	for (; n; n--) {
	pos = base_idx(base[state]) + (u8) *str++;
	if (check[pos] == state)
	state = next[pos];
	else
	state = def[state];
	if (accept[state])
	break;
	}
	}

	*retpos = str;
	return state;
	}

	#define inc_wb_pos(wb) \
	do { \
	wb->pos = (wb->pos + 1) & (WB_HISTORY_SIZE - 1); \
	wb->len = (wb->len + 1) & (WB_HISTORY_SIZE - 1); \
	} while (0)

	/* For DFAs that don't support extended tagging of states */
	static bool is_loop(struct match_workbuf *wb, aa_state_t state,
	unsigned int *adjust)
	{
	aa_state_t pos = wb->pos;
	aa_state_t i;

	if (wb->history[pos] < state)
	return false;

	for (i = 0; i <= wb->len; i++) {
	if (wb->history[pos] == state) {
	*adjust = i;
	return true;
	}
	if (pos == 0)
	pos = WB_HISTORY_SIZE;
	pos--;
	}

	*adjust = i;
	return true;
	}

	static aa_state_t leftmatch_fb(struct aa_dfa *dfa, aa_state_t start,
	const char str, struct match_workbuf wb,
	unsigned int *count)
	{
	u16 *def = DEFAULT_TABLE(dfa);
	u32 *base = BASE_TABLE(dfa);
	u16 *next = NEXT_TABLE(dfa);
	u16 *check = CHECK_TABLE(dfa);
	aa_state_t state = start, pos;

	AA_BUG(!dfa);
	AA_BUG(!str);
	AA_BUG(!wb);
	AA_BUG(!count);

	*count = 0;
	if (state == DFA_NOMATCH)
	return DFA_NOMATCH;

	/* current state is <state>, matching character str /
	if (dfa->tables[YYTD_ID_EC]) {
	/* Equivalence class table defined */
	u8 *equiv = EQUIV_TABLE(dfa);
	/* default is direct to next state */
	while (*str) {
	unsigned int adjust;

	wb->history[wb->pos] = state;
	pos = base_idx(base[state]) + equiv[(u8) *str++];
	if (check[pos] == state)
	state = next[pos];
	else
	state = def[state];
	if (is_loop(wb, state, &adjust)) {
	state = aa_dfa_match(dfa, state, str);
	*count -= adjust;
	goto out;
	}
	inc_wb_pos(wb);
	(*count)++;
	}
	} else {
	/* default is direct to next state */
	while (*str) {
	unsigned int adjust;

	wb->history[wb->pos] = state;
	pos = base_idx(base[state]) + (u8) *str++;
	if (check[pos] == state)
	state = next[pos];
	else
	state = def[state];
	if (is_loop(wb, state, &adjust)) {
	state = aa_dfa_match(dfa, state, str);
	*count -= adjust;
	goto out;
	}
	inc_wb_pos(wb);
	(*count)++;
	}
	}

	out:
	if (!state)
	*count = 0;
	return state;
	}

	/**
	* aa_dfa_leftmatch - traverse @dfa to find state @str stops at
	* @dfa: the dfa to match @str against (NOT NULL)
	* @start: the state of the dfa to start matching in
	* @str: the null terminated string of bytes to match against the dfa (NOT NULL)
	* @count: current count of longest left.
	*
	* aa_dfa_match will match @str against the dfa and return the state it
	* finished matching in. The final state can be used to look up the accepting
	* label, or as the start state of a continuing match.
	*
	* Returns: final state reached after input is consumed
	*/
	aa_state_t aa_dfa_leftmatch(struct aa_dfa *dfa, aa_state_t start,
	const char str, unsigned int count)
	{
	DEFINE_MATCH_WB(wb);

	/* TODO: match for extended state dfas */

	return leftmatch_fb(dfa, start, str, &wb, count);
	}