Merge tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg...

[mirror_ubuntu-bionic-kernel.git] / kernel / auditfilter.c

/* auditfilter.c -- filtering of audit events
 *
 * Copyright 2003-2004 Red Hat, Inc.
 * Copyright 2005 Hewlett-Packard Development Company, L.P.
 * Copyright 2005 IBM Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/kernel.h>
#include <linux/audit.h>
#include <linux/kthread.h>
#include <linux/mutex.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/netlink.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/security.h>
#include "audit.h"

/*
 * Locking model:
 *
 * audit_filter_mutex:
 *              Synchronizes writes and blocking reads of audit's filterlist
 *              data.  Rcu is used to traverse the filterlist and access
 *              contents of structs audit_entry, audit_watch and opaque
 *              LSM rules during filtering.  If modified, these structures
 *              must be copied and replace their counterparts in the filterlist.
 *              An audit_parent struct is not accessed during filtering, so may
 *              be written directly provided audit_filter_mutex is held.
 */

/* Audit filter lists, defined in <linux/audit.h> */
struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
        LIST_HEAD_INIT(audit_filter_list[0]),
        LIST_HEAD_INIT(audit_filter_list[1]),
        LIST_HEAD_INIT(audit_filter_list[2]),
        LIST_HEAD_INIT(audit_filter_list[3]),
        LIST_HEAD_INIT(audit_filter_list[4]),
        LIST_HEAD_INIT(audit_filter_list[5]),
#if AUDIT_NR_FILTERS != 6
#error Fix audit_filter_list initialiser
#endif
};
static struct list_head audit_rules_list[AUDIT_NR_FILTERS] = {
        LIST_HEAD_INIT(audit_rules_list[0]),
        LIST_HEAD_INIT(audit_rules_list[1]),
        LIST_HEAD_INIT(audit_rules_list[2]),
        LIST_HEAD_INIT(audit_rules_list[3]),
        LIST_HEAD_INIT(audit_rules_list[4]),
        LIST_HEAD_INIT(audit_rules_list[5]),
};

DEFINE_MUTEX(audit_filter_mutex);

static inline void audit_free_rule(struct audit_entry *e)
{
        int i;
        struct audit_krule *erule = &e->rule;

        /* some rules don't have associated watches */
        if (erule->watch)
                audit_put_watch(erule->watch);
        if (erule->fields)
                for (i = 0; i < erule->field_count; i++) {
                        struct audit_field *f = &erule->fields[i];
                        kfree(f->lsm_str);
                        security_audit_rule_free(f->lsm_rule);
                }
        kfree(erule->fields);
        kfree(erule->filterkey);
        kfree(e);
}

void audit_free_rule_rcu(struct rcu_head *head)
{
        struct audit_entry *e = container_of(head, struct audit_entry, rcu);
        audit_free_rule(e);
}

/* Initialize an audit filterlist entry. */
static inline struct audit_entry *audit_init_entry(u32 field_count)
{
        struct audit_entry *entry;
        struct audit_field *fields;

        entry = kzalloc(sizeof(*entry), GFP_KERNEL);
        if (unlikely(!entry))
                return NULL;

        fields = kzalloc(sizeof(*fields) * field_count, GFP_KERNEL);
        if (unlikely(!fields)) {
                kfree(entry);
                return NULL;
        }
        entry->rule.fields = fields;

        return entry;
}

/* Unpack a filter field's string representation from user-space
 * buffer. */
char *audit_unpack_string(void **bufp, size_t *remain, size_t len)
{
        char *str;

        if (!*bufp || (len == 0) || (len > *remain))
                return ERR_PTR(-EINVAL);

        /* Of the currently implemented string fields, PATH_MAX
         * defines the longest valid length.
         */
        if (len > PATH_MAX)
                return ERR_PTR(-ENAMETOOLONG);

        str = kmalloc(len + 1, GFP_KERNEL);
        if (unlikely(!str))
                return ERR_PTR(-ENOMEM);

        memcpy(str, *bufp, len);
        str[len] = 0;
        *bufp += len;
        *remain -= len;

        return str;
}

/* Translate an inode field to kernel respresentation. */
static inline int audit_to_inode(struct audit_krule *krule,
                                 struct audit_field *f)
{
        if (krule->listnr != AUDIT_FILTER_EXIT ||
            krule->watch || krule->inode_f || krule->tree ||
            (f->op != Audit_equal && f->op != Audit_not_equal))
                return -EINVAL;

        krule->inode_f = f;
        return 0;
}

static __u32 *classes[AUDIT_SYSCALL_CLASSES];

int __init audit_register_class(int class, unsigned *list)
{
        __u32 *p = kzalloc(AUDIT_BITMASK_SIZE * sizeof(__u32), GFP_KERNEL);
        if (!p)
                return -ENOMEM;
        while (*list != ~0U) {
                unsigned n = *list++;
                if (n >= AUDIT_BITMASK_SIZE * 32 - AUDIT_SYSCALL_CLASSES) {
                        kfree(p);
                        return -EINVAL;
                }
                p[AUDIT_WORD(n)] |= AUDIT_BIT(n);
        }
        if (class >= AUDIT_SYSCALL_CLASSES || classes[class]) {
                kfree(p);
                return -EINVAL;
        }
        classes[class] = p;
        return 0;
}

int audit_match_class(int class, unsigned syscall)
{
        if (unlikely(syscall >= AUDIT_BITMASK_SIZE * 32))
                return 0;
        if (unlikely(class >= AUDIT_SYSCALL_CLASSES || !classes[class]))
                return 0;
        return classes[class][AUDIT_WORD(syscall)] & AUDIT_BIT(syscall);
}

#ifdef CONFIG_AUDITSYSCALL
static inline int audit_match_class_bits(int class, u32 *mask)
{
        int i;

        if (classes[class]) {
                for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
                        if (mask[i] & classes[class][i])
                                return 0;
        }
        return 1;
}

static int audit_match_signal(struct audit_entry *entry)
{
        struct audit_field *arch = entry->rule.arch_f;

        if (!arch) {
                /* When arch is unspecified, we must check both masks on biarch
                 * as syscall number alone is ambiguous. */
                return (audit_match_class_bits(AUDIT_CLASS_SIGNAL,
                                               entry->rule.mask) &&
                        audit_match_class_bits(AUDIT_CLASS_SIGNAL_32,
                                               entry->rule.mask));
        }

        switch(audit_classify_arch(arch->val)) {
        case 0: /* native */
                return (audit_match_class_bits(AUDIT_CLASS_SIGNAL,
                                               entry->rule.mask));
        case 1: /* 32bit on biarch */
                return (audit_match_class_bits(AUDIT_CLASS_SIGNAL_32,
                                               entry->rule.mask));
        default:
                return 1;
        }
}
#endif

/* Common user-space to kernel rule translation. */
static inline struct audit_entry *audit_to_entry_common(struct audit_rule *rule)
{
        unsigned listnr;
        struct audit_entry *entry;
        int i, err;

        err = -EINVAL;
        listnr = rule->flags & ~AUDIT_FILTER_PREPEND;
        switch(listnr) {
        default:
                goto exit_err;
#ifdef CONFIG_AUDITSYSCALL
        case AUDIT_FILTER_ENTRY:
                if (rule->action == AUDIT_ALWAYS)
                        goto exit_err;
        case AUDIT_FILTER_EXIT:
        case AUDIT_FILTER_TASK:
#endif
        case AUDIT_FILTER_USER:
        case AUDIT_FILTER_TYPE:
                ;
        }
        if (unlikely(rule->action == AUDIT_POSSIBLE)) {
                printk(KERN_ERR "AUDIT_POSSIBLE is deprecated\n");
                goto exit_err;
        }
        if (rule->action != AUDIT_NEVER && rule->action != AUDIT_ALWAYS)
                goto exit_err;
        if (rule->field_count > AUDIT_MAX_FIELDS)
                goto exit_err;

        err = -ENOMEM;
        entry = audit_init_entry(rule->field_count);
        if (!entry)
                goto exit_err;

        entry->rule.flags = rule->flags & AUDIT_FILTER_PREPEND;
        entry->rule.listnr = listnr;
        entry->rule.action = rule->action;
        entry->rule.field_count = rule->field_count;

        for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
                entry->rule.mask[i] = rule->mask[i];

        for (i = 0; i < AUDIT_SYSCALL_CLASSES; i++) {
                int bit = AUDIT_BITMASK_SIZE * 32 - i - 1;
                __u32 *p = &entry->rule.mask[AUDIT_WORD(bit)];
                __u32 *class;

                if (!(*p & AUDIT_BIT(bit)))
                        continue;
                *p &= ~AUDIT_BIT(bit);
                class = classes[i];
                if (class) {
                        int j;
                        for (j = 0; j < AUDIT_BITMASK_SIZE; j++)
                                entry->rule.mask[j] |= class[j];
                }
        }

        return entry;

exit_err:
        return ERR_PTR(err);
}

static u32 audit_ops[] =
{
        [Audit_equal] = AUDIT_EQUAL,
        [Audit_not_equal] = AUDIT_NOT_EQUAL,
        [Audit_bitmask] = AUDIT_BIT_MASK,
        [Audit_bittest] = AUDIT_BIT_TEST,
        [Audit_lt] = AUDIT_LESS_THAN,
        [Audit_gt] = AUDIT_GREATER_THAN,
        [Audit_le] = AUDIT_LESS_THAN_OR_EQUAL,
        [Audit_ge] = AUDIT_GREATER_THAN_OR_EQUAL,
};

static u32 audit_to_op(u32 op)
{
        u32 n;
        for (n = Audit_equal; n < Audit_bad && audit_ops[n] != op; n++)
                ;
        return n;
}

/* check if an audit field is valid */
static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
{
        switch(f->type) {
        case AUDIT_MSGTYPE:
                if (entry->rule.listnr != AUDIT_FILTER_TYPE &&
                    entry->rule.listnr != AUDIT_FILTER_USER)
                        return -EINVAL;
                break;
        };

        switch(f->type) {
        default:
                return -EINVAL;
        case AUDIT_UID:
        case AUDIT_EUID:
        case AUDIT_SUID:
        case AUDIT_FSUID:
        case AUDIT_LOGINUID:
        case AUDIT_OBJ_UID:
        case AUDIT_GID:
        case AUDIT_EGID:
        case AUDIT_SGID:
        case AUDIT_FSGID:
        case AUDIT_OBJ_GID:
        case AUDIT_PID:
        case AUDIT_PERS:
        case AUDIT_MSGTYPE:
        case AUDIT_PPID:
        case AUDIT_DEVMAJOR:
        case AUDIT_DEVMINOR:
        case AUDIT_EXIT:
        case AUDIT_SUCCESS:
                /* bit ops are only useful on syscall args */
                if (f->op == Audit_bitmask || f->op == Audit_bittest)
                        return -EINVAL;
                break;
        case AUDIT_ARG0:
        case AUDIT_ARG1:
        case AUDIT_ARG2:
        case AUDIT_ARG3:
        case AUDIT_SUBJ_USER:
        case AUDIT_SUBJ_ROLE:
        case AUDIT_SUBJ_TYPE:
        case AUDIT_SUBJ_SEN:
        case AUDIT_SUBJ_CLR:
        case AUDIT_OBJ_USER:
        case AUDIT_OBJ_ROLE:
        case AUDIT_OBJ_TYPE:
        case AUDIT_OBJ_LEV_LOW:
        case AUDIT_OBJ_LEV_HIGH:
        case AUDIT_WATCH:
        case AUDIT_DIR:
        case AUDIT_FILTERKEY:
                break;
        case AUDIT_LOGINUID_SET:
                if ((f->val != 0) && (f->val != 1))
                        return -EINVAL;
        /* FALL THROUGH */
        case AUDIT_ARCH:
                if (f->op != Audit_not_equal && f->op != Audit_equal)
                        return -EINVAL;
                break;
        case AUDIT_PERM:
                if (f->val & ~15)
                        return -EINVAL;
                break;
        case AUDIT_FILETYPE:
                if (f->val & ~S_IFMT)
                        return -EINVAL;
                break;
        case AUDIT_FIELD_COMPARE:
                if (f->val > AUDIT_MAX_FIELD_COMPARE)
                        return -EINVAL;
                break;
        };
        return 0;
}

/* Translate struct audit_rule_data to kernel's rule respresentation. */
static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
                                               size_t datasz)
{
        int err = 0;
        struct audit_entry *entry;
        void *bufp;
        size_t remain = datasz - sizeof(struct audit_rule_data);
        int i;
        char *str;

        entry = audit_to_entry_common((struct audit_rule *)data);
        if (IS_ERR(entry))
                goto exit_nofree;

        bufp = data->buf;
        entry->rule.vers_ops = 2;
        for (i = 0; i < data->field_count; i++) {
                struct audit_field *f = &entry->rule.fields[i];

                err = -EINVAL;

                f->op = audit_to_op(data->fieldflags[i]);
                if (f->op == Audit_bad)
                        goto exit_free;

                f->type = data->fields[i];
                f->val = data->values[i];
                f->uid = INVALID_UID;
                f->gid = INVALID_GID;
                f->lsm_str = NULL;
                f->lsm_rule = NULL;

                /* Support legacy tests for a valid loginuid */
                if ((f->type == AUDIT_LOGINUID) && (f->val == ~0U)) {
                        f->type = AUDIT_LOGINUID_SET;
                        f->val = 0;
                }

                err = audit_field_valid(entry, f);
                if (err)
                        goto exit_free;

                err = -EINVAL;
                switch (f->type) {
                case AUDIT_LOGINUID:
                case AUDIT_UID:
                case AUDIT_EUID:
                case AUDIT_SUID:
                case AUDIT_FSUID:
                case AUDIT_OBJ_UID:
                        f->uid = make_kuid(current_user_ns(), f->val);
                        if (!uid_valid(f->uid))
                                goto exit_free;
                        break;
                case AUDIT_GID:
                case AUDIT_EGID:
                case AUDIT_SGID:
                case AUDIT_FSGID:
                case AUDIT_OBJ_GID:
                        f->gid = make_kgid(current_user_ns(), f->val);
                        if (!gid_valid(f->gid))
                                goto exit_free;
                        break;
                case AUDIT_ARCH:
                        entry->rule.arch_f = f;
                        break;
                case AUDIT_SUBJ_USER:
                case AUDIT_SUBJ_ROLE:
                case AUDIT_SUBJ_TYPE:
                case AUDIT_SUBJ_SEN:
                case AUDIT_SUBJ_CLR:
                case AUDIT_OBJ_USER:
                case AUDIT_OBJ_ROLE:
                case AUDIT_OBJ_TYPE:
                case AUDIT_OBJ_LEV_LOW:
                case AUDIT_OBJ_LEV_HIGH:
                        str = audit_unpack_string(&bufp, &remain, f->val);
                        if (IS_ERR(str))
                                goto exit_free;
                        entry->rule.buflen += f->val;

                        err = security_audit_rule_init(f->type, f->op, str,
                                                       (void **)&f->lsm_rule);
                        /* Keep currently invalid fields around in case they
                         * become valid after a policy reload. */
                        if (err == -EINVAL) {
                                printk(KERN_WARNING "audit rule for LSM "
                                       "\'%s\' is invalid\n",  str);
                                err = 0;
                        }
                        if (err) {
                                kfree(str);
                                goto exit_free;
                        } else
                                f->lsm_str = str;
                        break;
                case AUDIT_WATCH:
                        str = audit_unpack_string(&bufp, &remain, f->val);
                        if (IS_ERR(str))
                                goto exit_free;
                        entry->rule.buflen += f->val;

                        err = audit_to_watch(&entry->rule, str, f->val, f->op);
                        if (err) {
                                kfree(str);
                                goto exit_free;
                        }
                        break;
                case AUDIT_DIR:
                        str = audit_unpack_string(&bufp, &remain, f->val);
                        if (IS_ERR(str))
                                goto exit_free;
                        entry->rule.buflen += f->val;

                        err = audit_make_tree(&entry->rule, str, f->op);
                        kfree(str);
                        if (err)
                                goto exit_free;
                        break;
                case AUDIT_INODE:
                        err = audit_to_inode(&entry->rule, f);
                        if (err)
                                goto exit_free;
                        break;
                case AUDIT_FILTERKEY:
                        if (entry->rule.filterkey || f->val > AUDIT_MAX_KEY_LEN)
                                goto exit_free;
                        str = audit_unpack_string(&bufp, &remain, f->val);
                        if (IS_ERR(str))
                                goto exit_free;
                        entry->rule.buflen += f->val;
                        entry->rule.filterkey = str;
                        break;
                }
        }

        if (entry->rule.inode_f && entry->rule.inode_f->op == Audit_not_equal)
                entry->rule.inode_f = NULL;

exit_nofree:
        return entry;

exit_free:
        if (entry->rule.watch)
                audit_put_watch(entry->rule.watch); /* matches initial get */
        if (entry->rule.tree)
                audit_put_tree(entry->rule.tree); /* that's the temporary one */
        audit_free_rule(entry);
        return ERR_PTR(err);
}

/* Pack a filter field's string representation into data block. */
static inline size_t audit_pack_string(void **bufp, const char *str)
{
        size_t len = strlen(str);

        memcpy(*bufp, str, len);
        *bufp += len;

        return len;
}

/* Translate kernel rule respresentation to struct audit_rule_data. */
static struct audit_rule_data *audit_krule_to_data(struct audit_krule *krule)
{
        struct audit_rule_data *data;
        void *bufp;
        int i;

        data = kmalloc(sizeof(*data) + krule->buflen, GFP_KERNEL);
        if (unlikely(!data))
                return NULL;
        memset(data, 0, sizeof(*data));

        data->flags = krule->flags | krule->listnr;
        data->action = krule->action;
        data->field_count = krule->field_count;
        bufp = data->buf;
        for (i = 0; i < data->field_count; i++) {
                struct audit_field *f = &krule->fields[i];

                data->fields[i] = f->type;
                data->fieldflags[i] = audit_ops[f->op];
                switch(f->type) {
                case AUDIT_SUBJ_USER:
                case AUDIT_SUBJ_ROLE:
                case AUDIT_SUBJ_TYPE:
                case AUDIT_SUBJ_SEN:
                case AUDIT_SUBJ_CLR:
                case AUDIT_OBJ_USER:
                case AUDIT_OBJ_ROLE:
                case AUDIT_OBJ_TYPE:
                case AUDIT_OBJ_LEV_LOW:
                case AUDIT_OBJ_LEV_HIGH:
                        data->buflen += data->values[i] =
                                audit_pack_string(&bufp, f->lsm_str);
                        break;
                case AUDIT_WATCH:
                        data->buflen += data->values[i] =
                                audit_pack_string(&bufp,
                                                  audit_watch_path(krule->watch));
                        break;
                case AUDIT_DIR:
                        data->buflen += data->values[i] =
                                audit_pack_string(&bufp,
                                                  audit_tree_path(krule->tree));
                        break;
                case AUDIT_FILTERKEY:
                        data->buflen += data->values[i] =
                                audit_pack_string(&bufp, krule->filterkey);
                        break;
                default:
                        data->values[i] = f->val;
                }
        }
        for (i = 0; i < AUDIT_BITMASK_SIZE; i++) data->mask[i] = krule->mask[i];

        return data;
}

/* Compare two rules in kernel format.  Considered success if rules
 * don't match. */
static int audit_compare_rule(struct audit_krule *a, struct audit_krule *b)
{
        int i;

        if (a->flags != b->flags ||
            a->listnr != b->listnr ||
            a->action != b->action ||
            a->field_count != b->field_count)
                return 1;

        for (i = 0; i < a->field_count; i++) {
                if (a->fields[i].type != b->fields[i].type ||
                    a->fields[i].op != b->fields[i].op)
                        return 1;

                switch(a->fields[i].type) {
                case AUDIT_SUBJ_USER:
                case AUDIT_SUBJ_ROLE:
                case AUDIT_SUBJ_TYPE:
                case AUDIT_SUBJ_SEN:
                case AUDIT_SUBJ_CLR:
                case AUDIT_OBJ_USER:
                case AUDIT_OBJ_ROLE:
                case AUDIT_OBJ_TYPE:
                case AUDIT_OBJ_LEV_LOW:
                case AUDIT_OBJ_LEV_HIGH:
                        if (strcmp(a->fields[i].lsm_str, b->fields[i].lsm_str))
                                return 1;
                        break;
                case AUDIT_WATCH:
                        if (strcmp(audit_watch_path(a->watch),
                                   audit_watch_path(b->watch)))
                                return 1;
                        break;
                case AUDIT_DIR:
                        if (strcmp(audit_tree_path(a->tree),
                                   audit_tree_path(b->tree)))
                                return 1;
                        break;
                case AUDIT_FILTERKEY:
                        /* both filterkeys exist based on above type compare */
                        if (strcmp(a->filterkey, b->filterkey))
                                return 1;
                        break;
                case AUDIT_UID:
                case AUDIT_EUID:
                case AUDIT_SUID:
                case AUDIT_FSUID:
                case AUDIT_LOGINUID:
                case AUDIT_OBJ_UID:
                        if (!uid_eq(a->fields[i].uid, b->fields[i].uid))
                                return 1;
                        break;
                case AUDIT_GID:
                case AUDIT_EGID:
                case AUDIT_SGID:
                case AUDIT_FSGID:
                case AUDIT_OBJ_GID:
                        if (!gid_eq(a->fields[i].gid, b->fields[i].gid))
                                return 1;
                        break;
                default:
                        if (a->fields[i].val != b->fields[i].val)
                                return 1;
                }
        }

        for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
                if (a->mask[i] != b->mask[i])
                        return 1;

        return 0;
}

/* Duplicate LSM field information.  The lsm_rule is opaque, so must be
 * re-initialized. */
static inline int audit_dupe_lsm_field(struct audit_field *df,
                                           struct audit_field *sf)
{
        int ret = 0;
        char *lsm_str;

        /* our own copy of lsm_str */
        lsm_str = kstrdup(sf->lsm_str, GFP_KERNEL);
        if (unlikely(!lsm_str))
                return -ENOMEM;
        df->lsm_str = lsm_str;

        /* our own (refreshed) copy of lsm_rule */
        ret = security_audit_rule_init(df->type, df->op, df->lsm_str,
                                       (void **)&df->lsm_rule);
        /* Keep currently invalid fields around in case they
         * become valid after a policy reload. */
        if (ret == -EINVAL) {
                printk(KERN_WARNING "audit rule for LSM \'%s\' is "
                       "invalid\n", df->lsm_str);
                ret = 0;
        }

        return ret;
}

/* Duplicate an audit rule.  This will be a deep copy with the exception
 * of the watch - that pointer is carried over.  The LSM specific fields
 * will be updated in the copy.  The point is to be able to replace the old
 * rule with the new rule in the filterlist, then free the old rule.
 * The rlist element is undefined; list manipulations are handled apart from
 * the initial copy. */
struct audit_entry *audit_dupe_rule(struct audit_krule *old)
{
        u32 fcount = old->field_count;
        struct audit_entry *entry;
        struct audit_krule *new;
        char *fk;
        int i, err = 0;

        entry = audit_init_entry(fcount);
        if (unlikely(!entry))
                return ERR_PTR(-ENOMEM);

        new = &entry->rule;
        new->vers_ops = old->vers_ops;
        new->flags = old->flags;
        new->listnr = old->listnr;
        new->action = old->action;
        for (i = 0; i < AUDIT_BITMASK_SIZE; i++)
                new->mask[i] = old->mask[i];
        new->prio = old->prio;
        new->buflen = old->buflen;
        new->inode_f = old->inode_f;
        new->field_count = old->field_count;

        /*
         * note that we are OK with not refcounting here; audit_match_tree()
         * never dereferences tree and we can't get false positives there
         * since we'd have to have rule gone from the list *and* removed
         * before the chunks found by lookup had been allocated, i.e. before
         * the beginning of list scan.
         */
        new->tree = old->tree;
        memcpy(new->fields, old->fields, sizeof(struct audit_field) * fcount);

        /* deep copy this information, updating the lsm_rule fields, because
         * the originals will all be freed when the old rule is freed. */
        for (i = 0; i < fcount; i++) {
                switch (new->fields[i].type) {
                case AUDIT_SUBJ_USER:
                case AUDIT_SUBJ_ROLE:
                case AUDIT_SUBJ_TYPE:
                case AUDIT_SUBJ_SEN:
                case AUDIT_SUBJ_CLR:
                case AUDIT_OBJ_USER:
                case AUDIT_OBJ_ROLE:
                case AUDIT_OBJ_TYPE:
                case AUDIT_OBJ_LEV_LOW:
                case AUDIT_OBJ_LEV_HIGH:
                        err = audit_dupe_lsm_field(&new->fields[i],
                                                       &old->fields[i]);
                        break;
                case AUDIT_FILTERKEY:
                        fk = kstrdup(old->filterkey, GFP_KERNEL);
                        if (unlikely(!fk))
                                err = -ENOMEM;
                        else
                                new->filterkey = fk;
                }
                if (err) {
                        audit_free_rule(entry);
                        return ERR_PTR(err);
                }
        }

        if (old->watch) {
                audit_get_watch(old->watch);
                new->watch = old->watch;
        }

        return entry;
}

/* Find an existing audit rule.
 * Caller must hold audit_filter_mutex to prevent stale rule data. */
static struct audit_entry *audit_find_rule(struct audit_entry *entry,
                                           struct list_head **p)
{
        struct audit_entry *e, *found = NULL;
        struct list_head *list;
        int h;

        if (entry->rule.inode_f) {
                h = audit_hash_ino(entry->rule.inode_f->val);
                *p = list = &audit_inode_hash[h];
        } else if (entry->rule.watch) {
                /* we don't know the inode number, so must walk entire hash */
                for (h = 0; h < AUDIT_INODE_BUCKETS; h++) {
                        list = &audit_inode_hash[h];
                        list_for_each_entry(e, list, list)
                                if (!audit_compare_rule(&entry->rule, &e->rule)) {
                                        found = e;
                                        goto out;
                                }
                }
                goto out;
        } else {
                *p = list = &audit_filter_list[entry->rule.listnr];
        }

        list_for_each_entry(e, list, list)
                if (!audit_compare_rule(&entry->rule, &e->rule)) {
                        found = e;
                        goto out;
                }

out:
        return found;
}

static u64 prio_low = ~0ULL/2;
static u64 prio_high = ~0ULL/2 - 1;

/* Add rule to given filterlist if not a duplicate. */
static inline int audit_add_rule(struct audit_entry *entry)
{
        struct audit_entry *e;
        struct audit_watch *watch = entry->rule.watch;
        struct audit_tree *tree = entry->rule.tree;
        struct list_head *list;
        int err;
#ifdef CONFIG_AUDITSYSCALL
        int dont_count = 0;

        /* If either of these, don't count towards total */
        if (entry->rule.listnr == AUDIT_FILTER_USER ||
                entry->rule.listnr == AUDIT_FILTER_TYPE)
                dont_count = 1;
#endif

        mutex_lock(&audit_filter_mutex);
        e = audit_find_rule(entry, &list);
        if (e) {
                mutex_unlock(&audit_filter_mutex);
                err = -EEXIST;
                /* normally audit_add_tree_rule() will free it on failure */
                if (tree)
                        audit_put_tree(tree);
                goto error;
        }

        if (watch) {
                /* audit_filter_mutex is dropped and re-taken during this call */
                err = audit_add_watch(&entry->rule, &list);
                if (err) {
                        mutex_unlock(&audit_filter_mutex);
                        /*
                         * normally audit_add_tree_rule() will free it
                         * on failure
                         */
                        if (tree)
                                audit_put_tree(tree);
                        goto error;
                }
        }
        if (tree) {
                err = audit_add_tree_rule(&entry->rule);
                if (err) {
                        mutex_unlock(&audit_filter_mutex);
                        goto error;
                }
        }

        entry->rule.prio = ~0ULL;
        if (entry->rule.listnr == AUDIT_FILTER_EXIT) {
                if (entry->rule.flags & AUDIT_FILTER_PREPEND)
                        entry->rule.prio = ++prio_high;
                else
                        entry->rule.prio = --prio_low;
        }

        if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
                list_add(&entry->rule.list,
                         &audit_rules_list[entry->rule.listnr]);
                list_add_rcu(&entry->list, list);
                entry->rule.flags &= ~AUDIT_FILTER_PREPEND;
        } else {
                list_add_tail(&entry->rule.list,
                              &audit_rules_list[entry->rule.listnr]);
                list_add_tail_rcu(&entry->list, list);
        }
#ifdef CONFIG_AUDITSYSCALL
        if (!dont_count)
                audit_n_rules++;

        if (!audit_match_signal(entry))
                audit_signals++;
#endif
        mutex_unlock(&audit_filter_mutex);

        return 0;

error:
        if (watch)
                audit_put_watch(watch); /* tmp watch, matches initial get */
        return err;
}

/* Remove an existing rule from filterlist. */
static inline int audit_del_rule(struct audit_entry *entry)
{
        struct audit_entry  *e;
        struct audit_watch *watch = entry->rule.watch;
        struct audit_tree *tree = entry->rule.tree;
        struct list_head *list;
        int ret = 0;
#ifdef CONFIG_AUDITSYSCALL
        int dont_count = 0;

        /* If either of these, don't count towards total */
        if (entry->rule.listnr == AUDIT_FILTER_USER ||
                entry->rule.listnr == AUDIT_FILTER_TYPE)
                dont_count = 1;
#endif

        mutex_lock(&audit_filter_mutex);
        e = audit_find_rule(entry, &list);
        if (!e) {
                mutex_unlock(&audit_filter_mutex);
                ret = -ENOENT;
                goto out;
        }

        if (e->rule.watch)
                audit_remove_watch_rule(&e->rule);

        if (e->rule.tree)
                audit_remove_tree_rule(&e->rule);

        list_del_rcu(&e->list);
        list_del(&e->rule.list);
        call_rcu(&e->rcu, audit_free_rule_rcu);

#ifdef CONFIG_AUDITSYSCALL
        if (!dont_count)
                audit_n_rules--;

        if (!audit_match_signal(entry))
                audit_signals--;
#endif
        mutex_unlock(&audit_filter_mutex);

out:
        if (watch)
                audit_put_watch(watch); /* match initial get */
        if (tree)
                audit_put_tree(tree);   /* that's the temporary one */

        return ret;
}

/* List rules using struct audit_rule_data. */
static void audit_list_rules(int pid, int seq, struct sk_buff_head *q)
{
        struct sk_buff *skb;
        struct audit_krule *r;
        int i;

        /* This is a blocking read, so use audit_filter_mutex instead of rcu
         * iterator to sync with list writers. */
        for (i=0; i<AUDIT_NR_FILTERS; i++) {
                list_for_each_entry(r, &audit_rules_list[i], list) {
                        struct audit_rule_data *data;

                        data = audit_krule_to_data(r);
                        if (unlikely(!data))
                                break;
                        skb = audit_make_reply(pid, seq, AUDIT_LIST_RULES, 0, 1,
                                         data, sizeof(*data) + data->buflen);
                        if (skb)
                                skb_queue_tail(q, skb);
                        kfree(data);
                }
        }
        skb = audit_make_reply(pid, seq, AUDIT_LIST_RULES, 1, 1, NULL, 0);
        if (skb)
                skb_queue_tail(q, skb);
}

/* Log rule additions and removals */
static void audit_log_rule_change(char *action, struct audit_krule *rule, int res)
{
        struct audit_buffer *ab;
        uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(current));
        u32 sessionid = audit_get_sessionid(current);

        if (!audit_enabled)
                return;

        ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
        if (!ab)
                return;
        audit_log_format(ab, "auid=%u ses=%u" ,loginuid, sessionid);
        audit_log_task_context(ab);
        audit_log_format(ab, " op=");
        audit_log_string(ab, action);
        audit_log_key(ab, rule->filterkey);
        audit_log_format(ab, " list=%d res=%d", rule->listnr, res);
        audit_log_end(ab);
}

/**
 * audit_receive_filter - apply all rules to the specified message type
 * @type: audit message type
 * @pid: target pid for netlink audit messages
 * @seq: netlink audit message sequence (serial) number
 * @data: payload data
 * @datasz: size of payload data
 */
int audit_receive_filter(int type, int pid, int seq, void *data, size_t datasz)
{
        struct task_struct *tsk;
        struct audit_netlink_list *dest;
        int err = 0;
        struct audit_entry *entry;

        switch (type) {
        case AUDIT_LIST_RULES:
                /* We can't just spew out the rules here because we might fill
                 * the available socket buffer space and deadlock waiting for
                 * auditctl to read from it... which isn't ever going to
                 * happen if we're actually running in the context of auditctl
                 * trying to _send_ the stuff */

                dest = kmalloc(sizeof(struct audit_netlink_list), GFP_KERNEL);
                if (!dest)
                        return -ENOMEM;
                dest->pid = pid;
                skb_queue_head_init(&dest->q);

                mutex_lock(&audit_filter_mutex);
                audit_list_rules(pid, seq, &dest->q);
                mutex_unlock(&audit_filter_mutex);

                tsk = kthread_run(audit_send_list, dest, "audit_send_list");
                if (IS_ERR(tsk)) {
                        skb_queue_purge(&dest->q);
                        kfree(dest);
                        err = PTR_ERR(tsk);
                }
                break;
        case AUDIT_ADD_RULE:
                entry = audit_data_to_entry(data, datasz);
                if (IS_ERR(entry))
                        return PTR_ERR(entry);

                err = audit_add_rule(entry);
                audit_log_rule_change("add rule", &entry->rule, !err);
                if (err)
                        audit_free_rule(entry);
                break;
        case AUDIT_DEL_RULE:
                entry = audit_data_to_entry(data, datasz);
                if (IS_ERR(entry))
                        return PTR_ERR(entry);

                err = audit_del_rule(entry);
                audit_log_rule_change("remove rule", &entry->rule, !err);
                audit_free_rule(entry);
                break;
        default:
                return -EINVAL;
        }

        return err;
}

int audit_comparator(u32 left, u32 op, u32 right)
{
        switch (op) {
        case Audit_equal:
                return (left == right);
        case Audit_not_equal:
                return (left != right);
        case Audit_lt:
                return (left < right);
        case Audit_le:
                return (left <= right);
        case Audit_gt:
                return (left > right);
        case Audit_ge:
                return (left >= right);
        case Audit_bitmask:
                return (left & right);
        case Audit_bittest:
                return ((left & right) == right);
        default:
                BUG();
                return 0;
        }
}

int audit_uid_comparator(kuid_t left, u32 op, kuid_t right)
{
        switch (op) {
        case Audit_equal:
                return uid_eq(left, right);
        case Audit_not_equal:
                return !uid_eq(left, right);
        case Audit_lt:
                return uid_lt(left, right);
        case Audit_le:
                return uid_lte(left, right);
        case Audit_gt:
                return uid_gt(left, right);
        case Audit_ge:
                return uid_gte(left, right);
        case Audit_bitmask:
        case Audit_bittest:
        default:
                BUG();
                return 0;
        }
}

int audit_gid_comparator(kgid_t left, u32 op, kgid_t right)
{
        switch (op) {
        case Audit_equal:
                return gid_eq(left, right);
        case Audit_not_equal:
                return !gid_eq(left, right);
        case Audit_lt:
                return gid_lt(left, right);
        case Audit_le:
                return gid_lte(left, right);
        case Audit_gt:
                return gid_gt(left, right);
        case Audit_ge:
                return gid_gte(left, right);
        case Audit_bitmask:
        case Audit_bittest:
        default:
                BUG();
                return 0;
        }
}

/**
 * parent_len - find the length of the parent portion of a pathname
 * @path: pathname of which to determine length
 */
int parent_len(const char *path)
{
        int plen;
        const char *p;

        plen = strlen(path);

        if (plen == 0)
                return plen;

        /* disregard trailing slashes */
        p = path + plen - 1;
        while ((*p == '/') && (p > path))
                p--;

        /* walk backward until we find the next slash or hit beginning */
        while ((*p != '/') && (p > path))
                p--;

        /* did we find a slash? Then increment to include it in path */
        if (*p == '/')
                p++;

        return p - path;
}

/**
 * audit_compare_dname_path - compare given dentry name with last component in
 *                            given path. Return of 0 indicates a match.
 * @dname:      dentry name that we're comparing
 * @path:       full pathname that we're comparing
 * @parentlen:  length of the parent if known. Passing in AUDIT_NAME_FULL
 *              here indicates that we must compute this value.
 */
int audit_compare_dname_path(const char *dname, const char *path, int parentlen)
{
        int dlen, pathlen;
        const char *p;

        dlen = strlen(dname);
        pathlen = strlen(path);
        if (pathlen < dlen)
                return 1;

        parentlen = parentlen == AUDIT_NAME_FULL ? parent_len(path) : parentlen;
        if (pathlen - parentlen != dlen)
                return 1;

        p = path + parentlen;

        return strncmp(p, dname, dlen);
}

static int audit_filter_user_rules(struct audit_krule *rule, int type,
                                   enum audit_state *state)
{
        int i;

        for (i = 0; i < rule->field_count; i++) {
                struct audit_field *f = &rule->fields[i];
                int result = 0;
                u32 sid;

                switch (f->type) {
                case AUDIT_PID:
                        result = audit_comparator(task_pid_vnr(current), f->op, f->val);
                        break;
                case AUDIT_UID:
                        result = audit_uid_comparator(current_uid(), f->op, f->uid);
                        break;
                case AUDIT_GID:
                        result = audit_gid_comparator(current_gid(), f->op, f->gid);
                        break;
                case AUDIT_LOGINUID:
                        result = audit_uid_comparator(audit_get_loginuid(current),
                                                  f->op, f->uid);
                        break;
                case AUDIT_LOGINUID_SET:
                        result = audit_comparator(audit_loginuid_set(current),
                                                  f->op, f->val);
                        break;
                case AUDIT_MSGTYPE:
                        result = audit_comparator(type, f->op, f->val);
                        break;
                case AUDIT_SUBJ_USER:
                case AUDIT_SUBJ_ROLE:
                case AUDIT_SUBJ_TYPE:
                case AUDIT_SUBJ_SEN:
                case AUDIT_SUBJ_CLR:
                        if (f->lsm_rule) {
                                security_task_getsecid(current, &sid);
                                result = security_audit_rule_match(sid,
                                                                   f->type,
                                                                   f->op,
                                                                   f->lsm_rule,
                                                                   NULL);
                        }
                        break;
                }

                if (!result)
                        return 0;
        }
        switch (rule->action) {
        case AUDIT_NEVER:    *state = AUDIT_DISABLED;       break;
        case AUDIT_ALWAYS:   *state = AUDIT_RECORD_CONTEXT; break;
        }
        return 1;
}

int audit_filter_user(int type)
{
        enum audit_state state = AUDIT_DISABLED;
        struct audit_entry *e;
        int ret = 1;

        rcu_read_lock();
        list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) {
                if (audit_filter_user_rules(&e->rule, type, &state)) {
                        if (state == AUDIT_DISABLED)
                                ret = 0;
                        break;
                }
        }
        rcu_read_unlock();

        return ret; /* Audit by default */
}

int audit_filter_type(int type)
{
        struct audit_entry *e;
        int result = 0;

        rcu_read_lock();
        if (list_empty(&audit_filter_list[AUDIT_FILTER_TYPE]))
                goto unlock_and_return;

        list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TYPE],
                                list) {
                int i;
                for (i = 0; i < e->rule.field_count; i++) {
                        struct audit_field *f = &e->rule.fields[i];
                        if (f->type == AUDIT_MSGTYPE) {
                                result = audit_comparator(type, f->op, f->val);
                                if (!result)
                                        break;
                        }
                }
                if (result)
                        goto unlock_and_return;
        }
unlock_and_return:
        rcu_read_unlock();
        return result;
}

static int update_lsm_rule(struct audit_krule *r)
{
        struct audit_entry *entry = container_of(r, struct audit_entry, rule);
        struct audit_entry *nentry;
        int err = 0;

        if (!security_audit_rule_known(r))
                return 0;

        nentry = audit_dupe_rule(r);
        if (IS_ERR(nentry)) {
                /* save the first error encountered for the
                 * return value */
                err = PTR_ERR(nentry);
                audit_panic("error updating LSM filters");
                if (r->watch)
                        list_del(&r->rlist);
                list_del_rcu(&entry->list);
                list_del(&r->list);
        } else {
                if (r->watch || r->tree)
                        list_replace_init(&r->rlist, &nentry->rule.rlist);
                list_replace_rcu(&entry->list, &nentry->list);
                list_replace(&r->list, &nentry->rule.list);
        }
        call_rcu(&entry->rcu, audit_free_rule_rcu);

        return err;
}

/* This function will re-initialize the lsm_rule field of all applicable rules.
 * It will traverse the filter lists serarching for rules that contain LSM
 * specific filter fields.  When such a rule is found, it is copied, the
 * LSM field is re-initialized, and the old rule is replaced with the
 * updated rule. */
int audit_update_lsm_rules(void)
{
        struct audit_krule *r, *n;
        int i, err = 0;

        /* audit_filter_mutex synchronizes the writers */
        mutex_lock(&audit_filter_mutex);

        for (i = 0; i < AUDIT_NR_FILTERS; i++) {
                list_for_each_entry_safe(r, n, &audit_rules_list[i], list) {
                        int res = update_lsm_rule(r);
                        if (!err)
                                err = res;
                }
        }
        mutex_unlock(&audit_filter_mutex);

        return err;
}