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-rw-r--r--security/apparmor/match.c792
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);
+}