Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 792 insertions, 0 deletions

diff --git a/security/apparmor/match.c b/security/apparmor/match.c
new file mode 100644
index 000000000..3e9e1eaf9
--- /dev/null
+++ b/security/apparmor/match.c
@@ -0,0 +1,792 @@
+// 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 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 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
+ */
+unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int 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);
+	unsigned int state = start;
+
+	if (state == 0)
+		return 0;
+
+	/* 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
+ */
+unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
+			  const char *str)
+{
+	u16 *def = DEFAULT_TABLE(dfa);
+	u32 *base = BASE_TABLE(dfa);
+	u16 *next = NEXT_TABLE(dfa);
+	u16 *check = CHECK_TABLE(dfa);
+	unsigned int state = start;
+
+	if (state == 0)
+		return 0;
+
+	/* 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
+ */
+unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int 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;
+}
+
+unsigned int aa_dfa_outofband_transition(struct aa_dfa *dfa, unsigned int 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
+ */
+unsigned int aa_dfa_match_until(struct aa_dfa *dfa, unsigned int 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);
+	unsigned int state = start, pos;
+
+	if (state == 0)
+		return 0;
+
+	/* 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
+ */
+unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int 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);
+	unsigned int state = start, pos;
+
+	*retpos = NULL;
+	if (state == 0)
+		return 0;
+
+	/* 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, unsigned int state,
+		    unsigned int *adjust)
+{
+	unsigned int pos = wb->pos;
+	unsigned int 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 unsigned int leftmatch_fb(struct aa_dfa *dfa, unsigned int 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);
+	unsigned int state = start, pos;
+
+	AA_BUG(!dfa);
+	AA_BUG(!str);
+	AA_BUG(!wb);
+	AA_BUG(!count);
+
+	*count = 0;
+	if (state == 0)
+		return 0;
+
+	/* 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
+ */
+unsigned int aa_dfa_leftmatch(struct aa_dfa *dfa, unsigned int 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);
+}