[PATCH] Collect more inode information during syscall processing.

[linux-2.6] / kernel / auditsc.c

/* auditsc.c -- System-call auditing support
 * Handles all system-call specific auditing features.
 *
 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
 * Copyright 2005 Hewlett-Packard Development Company, L.P.
 * Copyright (C) 2005 IBM Corporation
 * All Rights Reserved.
 *
 * 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
 *
 * Written by Rickard E. (Rik) Faith <faith@redhat.com>
 *
 * Many of the ideas implemented here are from Stephen C. Tweedie,
 * especially the idea of avoiding a copy by using getname.
 *
 * The method for actual interception of syscall entry and exit (not in
 * this file -- see entry.S) is based on a GPL'd patch written by
 * okir@suse.de and Copyright 2003 SuSE Linux AG.
 *
 * The support of additional filter rules compares (>, <, >=, <=) was
 * added by Dustin Kirkland <dustin.kirkland@us.ibm.com>, 2005.
 *
 * Modified by Amy Griffis <amy.griffis@hp.com> to collect additional
 * filesystem information.
 */

#include <linux/init.h>
#include <asm/types.h>
#include <asm/atomic.h>
#include <asm/types.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/socket.h>
#include <linux/audit.h>
#include <linux/personality.h>
#include <linux/time.h>
#include <linux/kthread.h>
#include <linux/netlink.h>
#include <linux/compiler.h>
#include <asm/unistd.h>

/* 0 = no checking
   1 = put_count checking
   2 = verbose put_count checking
*/
#define AUDIT_DEBUG 0

/* No syscall auditing will take place unless audit_enabled != 0. */
extern int audit_enabled;

/* AUDIT_NAMES is the number of slots we reserve in the audit_context
 * for saving names from getname(). */
#define AUDIT_NAMES    20

/* AUDIT_NAMES_RESERVED is the number of slots we reserve in the
 * audit_context from being used for nameless inodes from
 * path_lookup. */
#define AUDIT_NAMES_RESERVED 7

/* At task start time, the audit_state is set in the audit_context using
   a per-task filter.  At syscall entry, the audit_state is augmented by
   the syscall filter. */
enum audit_state {
        AUDIT_DISABLED,         /* Do not create per-task audit_context.
                                 * No syscall-specific audit records can
                                 * be generated. */
        AUDIT_SETUP_CONTEXT,    /* Create the per-task audit_context,
                                 * but don't necessarily fill it in at
                                 * syscall entry time (i.e., filter
                                 * instead). */
        AUDIT_BUILD_CONTEXT,    /* Create the per-task audit_context,
                                 * and always fill it in at syscall
                                 * entry time.  This makes a full
                                 * syscall record available if some
                                 * other part of the kernel decides it
                                 * should be recorded. */
        AUDIT_RECORD_CONTEXT    /* Create the per-task audit_context,
                                 * always fill it in at syscall entry
                                 * time, and always write out the audit
                                 * record at syscall exit time.  */
};

/* When fs/namei.c:getname() is called, we store the pointer in name and
 * we don't let putname() free it (instead we free all of the saved
 * pointers at syscall exit time).
 *
 * Further, in fs/namei.c:path_lookup() we store the inode and device. */
struct audit_names {
        const char      *name;
        unsigned long   ino;
        unsigned long   pino;
        dev_t           dev;
        umode_t         mode;
        uid_t           uid;
        gid_t           gid;
        dev_t           rdev;
};

struct audit_aux_data {
        struct audit_aux_data   *next;
        int                     type;
};

#define AUDIT_AUX_IPCPERM       0

struct audit_aux_data_ipcctl {
        struct audit_aux_data   d;
        struct ipc_perm         p;
        unsigned long           qbytes;
        uid_t                   uid;
        gid_t                   gid;
        mode_t                  mode;
};

struct audit_aux_data_socketcall {
        struct audit_aux_data   d;
        int                     nargs;
        unsigned long           args[0];
};

struct audit_aux_data_sockaddr {
        struct audit_aux_data   d;
        int                     len;
        char                    a[0];
};

struct audit_aux_data_path {
        struct audit_aux_data   d;
        struct dentry           *dentry;
        struct vfsmount         *mnt;
};

/* The per-task audit context. */
struct audit_context {
        int                 in_syscall; /* 1 if task is in a syscall */
        enum audit_state    state;
        unsigned int        serial;     /* serial number for record */
        struct timespec     ctime;      /* time of syscall entry */
        uid_t               loginuid;   /* login uid (identity) */
        int                 major;      /* syscall number */
        unsigned long       argv[4];    /* syscall arguments */
        int                 return_valid; /* return code is valid */
        long                return_code;/* syscall return code */
        int                 auditable;  /* 1 if record should be written */
        int                 name_count;
        struct audit_names  names[AUDIT_NAMES];
        struct dentry *     pwd;
        struct vfsmount *   pwdmnt;
        struct audit_context *previous; /* For nested syscalls */
        struct audit_aux_data *aux;

                                /* Save things to print about task_struct */
        pid_t               pid;
        uid_t               uid, euid, suid, fsuid;
        gid_t               gid, egid, sgid, fsgid;
        unsigned long       personality;
        int                 arch;

#if AUDIT_DEBUG
        int                 put_count;
        int                 ino_count;
#endif
};

                                /* Public API */
/* There are three lists of rules -- one to search at task creation
 * time, one to search at syscall entry time, and another to search at
 * syscall exit time. */
static 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]),
#if AUDIT_NR_FILTERS != 5
#error Fix audit_filter_list initialiser
#endif
};

struct audit_entry {
        struct list_head  list;
        struct rcu_head   rcu;
        struct audit_rule rule;
};

extern int audit_pid;

/* Copy rule from user-space to kernel-space.  Called from 
 * audit_add_rule during AUDIT_ADD. */
static inline int audit_copy_rule(struct audit_rule *d, struct audit_rule *s)
{
        int i;

        if (s->action != AUDIT_NEVER
            && s->action != AUDIT_POSSIBLE
            && s->action != AUDIT_ALWAYS)
                return -1;
        if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS)
                return -1;
        if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS)
                return -1;

        d->flags        = s->flags;
        d->action       = s->action;
        d->field_count  = s->field_count;
        for (i = 0; i < d->field_count; i++) {
                d->fields[i] = s->fields[i];
                d->values[i] = s->values[i];
        }
        for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i];
        return 0;
}

/* Check to see if two rules are identical.  It is called from
 * audit_add_rule during AUDIT_ADD and 
 * audit_del_rule during AUDIT_DEL. */
static inline int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
{
        int i;

        if (a->flags != b->flags)
                return 1;

        if (a->action != b->action)
                return 1;

        if (a->field_count != b->field_count)
                return 1;

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

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

        return 0;
}

/* Note that audit_add_rule and audit_del_rule are called via
 * audit_receive() in audit.c, and are protected by
 * audit_netlink_sem. */
static inline int audit_add_rule(struct audit_rule *rule,
                                  struct list_head *list)
{
        struct audit_entry  *entry;
        int i;

        /* Do not use the _rcu iterator here, since this is the only
         * addition routine. */
        list_for_each_entry(entry, list, list) {
                if (!audit_compare_rule(rule, &entry->rule)) {
                        return -EEXIST;
                }
        }

        for (i = 0; i < rule->field_count; i++) {
                if (rule->fields[i] & AUDIT_UNUSED_BITS)
                        return -EINVAL;
                if ( rule->fields[i] & AUDIT_NEGATE )
                        rule->fields[i] |= AUDIT_NOT_EQUAL;
                else if ( (rule->fields[i] & AUDIT_OPERATORS) == 0 )
                        rule->fields[i] |= AUDIT_EQUAL;
                rule->fields[i] &= (~AUDIT_NEGATE);
        }

        if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL)))
                return -ENOMEM;
        if (audit_copy_rule(&entry->rule, rule)) {
                kfree(entry);
                return -EINVAL;
        }

        if (entry->rule.flags & AUDIT_FILTER_PREPEND) {
                entry->rule.flags &= ~AUDIT_FILTER_PREPEND;
                list_add_rcu(&entry->list, list);
        } else {
                list_add_tail_rcu(&entry->list, list);
        }

        return 0;
}

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

/* Note that audit_add_rule and audit_del_rule are called via
 * audit_receive() in audit.c, and are protected by
 * audit_netlink_sem. */
static inline int audit_del_rule(struct audit_rule *rule,
                                 struct list_head *list)
{
        struct audit_entry  *e;

        /* Do not use the _rcu iterator here, since this is the only
         * deletion routine. */
        list_for_each_entry(e, list, list) {
                if (!audit_compare_rule(rule, &e->rule)) {
                        list_del_rcu(&e->list);
                        call_rcu(&e->rcu, audit_free_rule);
                        return 0;
                }
        }
        return -ENOENT;         /* No matching rule */
}

static int audit_list_rules(void *_dest)
{
        int pid, seq;
        int *dest = _dest;
        struct audit_entry *entry;
        int i;

        pid = dest[0];
        seq = dest[1];
        kfree(dest);

        down(&audit_netlink_sem);

        /* The *_rcu iterators not needed here because we are
           always called with audit_netlink_sem held. */
        for (i=0; i<AUDIT_NR_FILTERS; i++) {
                list_for_each_entry(entry, &audit_filter_list[i], list)
                        audit_send_reply(pid, seq, AUDIT_LIST, 0, 1,
                                         &entry->rule, sizeof(entry->rule));
        }
        audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0);
        
        up(&audit_netlink_sem);
        return 0;
}

/**
 * audit_receive_filter - apply all rules to the specified message type
 * @type: audit message type
 * @pid: target pid for netlink audit messages
 * @uid: target uid for netlink audit messages
 * @seq: netlink audit message sequence (serial) number
 * @data: payload data
 * @loginuid: loginuid of sender
 */
int audit_receive_filter(int type, int pid, int uid, int seq, void *data,
                                                        uid_t loginuid)
{
        struct task_struct *tsk;
        int *dest;
        int                err = 0;
        unsigned listnr;

        switch (type) {
        case AUDIT_LIST:
                /* 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(2 * sizeof(int), GFP_KERNEL);
                if (!dest)
                        return -ENOMEM;
                dest[0] = pid;
                dest[1] = seq;

                tsk = kthread_run(audit_list_rules, dest, "audit_list_rules");
                if (IS_ERR(tsk)) {
                        kfree(dest);
                        err = PTR_ERR(tsk);
                }
                break;
        case AUDIT_ADD:
                listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
                if (listnr >= AUDIT_NR_FILTERS)
                        return -EINVAL;

                err = audit_add_rule(data, &audit_filter_list[listnr]);
                if (!err)
                        audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
                                  "auid=%u added an audit rule\n", loginuid);
                break;
        case AUDIT_DEL:
                listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND;
                if (listnr >= AUDIT_NR_FILTERS)
                        return -EINVAL;

                err = audit_del_rule(data, &audit_filter_list[listnr]);
                if (!err)
                        audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
                                  "auid=%u removed an audit rule\n", loginuid);
                break;
        default:
                return -EINVAL;
        }

        return err;
}

static int audit_comparator(const u32 left, const u32 op, const u32 right)
{
        switch (op) {
        case AUDIT_EQUAL:
                return (left == right);
        case AUDIT_NOT_EQUAL:
                return (left != right);
        case AUDIT_LESS_THAN:
                return (left < right);
        case AUDIT_LESS_THAN_OR_EQUAL:
                return (left <= right);
        case AUDIT_GREATER_THAN:
                return (left > right);
        case AUDIT_GREATER_THAN_OR_EQUAL:
                return (left >= right);
        default:
                return -EINVAL;
        }
}

/* Compare a task_struct with an audit_rule.  Return 1 on match, 0
 * otherwise. */
static int audit_filter_rules(struct task_struct *tsk,
                              struct audit_rule *rule,
                              struct audit_context *ctx,
                              enum audit_state *state)
{
        int i, j;

        for (i = 0; i < rule->field_count; i++) {
                u32 field  = rule->fields[i] & ~AUDIT_OPERATORS;
                u32 op  = rule->fields[i] & AUDIT_OPERATORS;
                u32 value  = rule->values[i];
                int result = 0;

                switch (field) {
                case AUDIT_PID:
                        result = audit_comparator(tsk->pid, op, value);
                        break;
                case AUDIT_UID:
                        result = audit_comparator(tsk->uid, op, value);
                        break;
                case AUDIT_EUID:
                        result = audit_comparator(tsk->euid, op, value);
                        break;
                case AUDIT_SUID:
                        result = audit_comparator(tsk->suid, op, value);
                        break;
                case AUDIT_FSUID:
                        result = audit_comparator(tsk->fsuid, op, value);
                        break;
                case AUDIT_GID:
                        result = audit_comparator(tsk->gid, op, value);
                        break;
                case AUDIT_EGID:
                        result = audit_comparator(tsk->egid, op, value);
                        break;
                case AUDIT_SGID:
                        result = audit_comparator(tsk->sgid, op, value);
                        break;
                case AUDIT_FSGID:
                        result = audit_comparator(tsk->fsgid, op, value);
                        break;
                case AUDIT_PERS:
                        result = audit_comparator(tsk->personality, op, value);
                        break;
                case AUDIT_ARCH:
                        if (ctx)
                                result = audit_comparator(ctx->arch, op, value);
                        break;

                case AUDIT_EXIT:
                        if (ctx && ctx->return_valid)
                                result = audit_comparator(ctx->return_code, op, value);
                        break;
                case AUDIT_SUCCESS:
                        if (ctx && ctx->return_valid) {
                                if (value)
                                        result = audit_comparator(ctx->return_valid, op, AUDITSC_SUCCESS);
                                else
                                        result = audit_comparator(ctx->return_valid, op, AUDITSC_FAILURE);
                        }
                        break;
                case AUDIT_DEVMAJOR:
                        if (ctx) {
                                for (j = 0; j < ctx->name_count; j++) {
                                        if (audit_comparator(MAJOR(ctx->names[j].dev),  op, value)) {
                                                ++result;
                                                break;
                                        }
                                }
                        }
                        break;
                case AUDIT_DEVMINOR:
                        if (ctx) {
                                for (j = 0; j < ctx->name_count; j++) {
                                        if (audit_comparator(MINOR(ctx->names[j].dev), op, value)) {
                                                ++result;
                                                break;
                                        }
                                }
                        }
                        break;
                case AUDIT_INODE:
                        if (ctx) {
                                for (j = 0; j < ctx->name_count; j++) {
                                        if (audit_comparator(ctx->names[j].ino, op, value) ||
                                            audit_comparator(ctx->names[j].pino, op, value)) {
                                                ++result;
                                                break;
                                        }
                                }
                        }
                        break;
                case AUDIT_LOGINUID:
                        result = 0;
                        if (ctx)
                                result = audit_comparator(ctx->loginuid, op, value);
                        break;
                case AUDIT_ARG0:
                case AUDIT_ARG1:
                case AUDIT_ARG2:
                case AUDIT_ARG3:
                        if (ctx)
                                result = audit_comparator(ctx->argv[field-AUDIT_ARG0], op, value);
                        break;
                }

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

/* At process creation time, we can determine if system-call auditing is
 * completely disabled for this task.  Since we only have the task
 * structure at this point, we can only check uid and gid.
 */
static enum audit_state audit_filter_task(struct task_struct *tsk)
{
        struct audit_entry *e;
        enum audit_state   state;

        rcu_read_lock();
        list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TASK], list) {
                if (audit_filter_rules(tsk, &e->rule, NULL, &state)) {
                        rcu_read_unlock();
                        return state;
                }
        }
        rcu_read_unlock();
        return AUDIT_BUILD_CONTEXT;
}

/* At syscall entry and exit time, this filter is called if the
 * audit_state is not low enough that auditing cannot take place, but is
 * also not high enough that we already know we have to write an audit
 * record (i.e., the state is AUDIT_SETUP_CONTEXT or AUDIT_BUILD_CONTEXT).
 */
static enum audit_state audit_filter_syscall(struct task_struct *tsk,
                                             struct audit_context *ctx,
                                             struct list_head *list)
{
        struct audit_entry *e;
        enum audit_state state;

        if (audit_pid && tsk->tgid == audit_pid)
                return AUDIT_DISABLED;

        rcu_read_lock();
        if (!list_empty(list)) {
                int word = AUDIT_WORD(ctx->major);
                int bit  = AUDIT_BIT(ctx->major);

                list_for_each_entry_rcu(e, list, list) {
                        if ((e->rule.mask[word] & bit) == bit
                                        && audit_filter_rules(tsk, &e->rule, ctx, &state)) {
                                rcu_read_unlock();
                                return state;
                        }
                }
        }
        rcu_read_unlock();
        return AUDIT_BUILD_CONTEXT;
}

static int audit_filter_user_rules(struct netlink_skb_parms *cb,
                                   struct audit_rule *rule,
                                   enum audit_state *state)
{
        int i;

        for (i = 0; i < rule->field_count; i++) {
                u32 field  = rule->fields[i] & ~AUDIT_OPERATORS;
                u32 op  = rule->fields[i] & AUDIT_OPERATORS;
                u32 value  = rule->values[i];
                int result = 0;

                switch (field) {
                case AUDIT_PID:
                        result = audit_comparator(cb->creds.pid, op, value);
                        break;
                case AUDIT_UID:
                        result = audit_comparator(cb->creds.uid, op, value);
                        break;
                case AUDIT_GID:
                        result = audit_comparator(cb->creds.gid, op, value);
                        break;
                case AUDIT_LOGINUID:
                        result = audit_comparator(cb->loginuid, op, value);
                        break;
                }

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

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

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

        return ret; /* Audit by default */
}

/* This should be called with task_lock() held. */
static inline struct audit_context *audit_get_context(struct task_struct *tsk,
                                                      int return_valid,
                                                      int return_code)
{
        struct audit_context *context = tsk->audit_context;

        if (likely(!context))
                return NULL;
        context->return_valid = return_valid;
        context->return_code  = return_code;

        if (context->in_syscall && !context->auditable) {
                enum audit_state state;
                state = audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_EXIT]);
                if (state == AUDIT_RECORD_CONTEXT)
                        context->auditable = 1;
        }

        context->pid = tsk->pid;
        context->uid = tsk->uid;
        context->gid = tsk->gid;
        context->euid = tsk->euid;
        context->suid = tsk->suid;
        context->fsuid = tsk->fsuid;
        context->egid = tsk->egid;
        context->sgid = tsk->sgid;
        context->fsgid = tsk->fsgid;
        context->personality = tsk->personality;
        tsk->audit_context = NULL;
        return context;
}

static inline void audit_free_names(struct audit_context *context)
{
        int i;

#if AUDIT_DEBUG == 2
        if (context->auditable
            ||context->put_count + context->ino_count != context->name_count) {
                printk(KERN_ERR "%s:%d(:%d): major=%d in_syscall=%d"
                       " name_count=%d put_count=%d"
                       " ino_count=%d [NOT freeing]\n",
                       __FILE__, __LINE__,
                       context->serial, context->major, context->in_syscall,
                       context->name_count, context->put_count,
                       context->ino_count);
                for (i = 0; i < context->name_count; i++)
                        printk(KERN_ERR "names[%d] = %p = %s\n", i,
                               context->names[i].name,
                               context->names[i].name ?: "(null)");
                dump_stack();
                return;
        }
#endif
#if AUDIT_DEBUG
        context->put_count  = 0;
        context->ino_count  = 0;
#endif

        for (i = 0; i < context->name_count; i++)
                if (context->names[i].name)
                        __putname(context->names[i].name);
        context->name_count = 0;
        if (context->pwd)
                dput(context->pwd);
        if (context->pwdmnt)
                mntput(context->pwdmnt);
        context->pwd = NULL;
        context->pwdmnt = NULL;
}

static inline void audit_free_aux(struct audit_context *context)
{
        struct audit_aux_data *aux;

        while ((aux = context->aux)) {
                if (aux->type == AUDIT_AVC_PATH) {
                        struct audit_aux_data_path *axi = (void *)aux;
                        dput(axi->dentry);
                        mntput(axi->mnt);
                }
                context->aux = aux->next;
                kfree(aux);
        }
}

static inline void audit_zero_context(struct audit_context *context,
                                      enum audit_state state)
{
        uid_t loginuid = context->loginuid;

        memset(context, 0, sizeof(*context));
        context->state      = state;
        context->loginuid   = loginuid;
}

static inline struct audit_context *audit_alloc_context(enum audit_state state)
{
        struct audit_context *context;

        if (!(context = kmalloc(sizeof(*context), GFP_KERNEL)))
                return NULL;
        audit_zero_context(context, state);
        return context;
}

/**
 * audit_alloc - allocate an audit context block for a task
 * @tsk: task
 *
 * Filter on the task information and allocate a per-task audit context
 * if necessary.  Doing so turns on system call auditing for the
 * specified task.  This is called from copy_process, so no lock is
 * needed.
 */
int audit_alloc(struct task_struct *tsk)
{
        struct audit_context *context;
        enum audit_state     state;

        if (likely(!audit_enabled))
                return 0; /* Return if not auditing. */

        state = audit_filter_task(tsk);
        if (likely(state == AUDIT_DISABLED))
                return 0;

        if (!(context = audit_alloc_context(state))) {
                audit_log_lost("out of memory in audit_alloc");
                return -ENOMEM;
        }

                                /* Preserve login uid */
        context->loginuid = -1;
        if (current->audit_context)
                context->loginuid = current->audit_context->loginuid;

        tsk->audit_context  = context;
        set_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
        return 0;
}

static inline void audit_free_context(struct audit_context *context)
{
        struct audit_context *previous;
        int                  count = 0;

        do {
                previous = context->previous;
                if (previous || (count &&  count < 10)) {
                        ++count;
                        printk(KERN_ERR "audit(:%d): major=%d name_count=%d:"
                               " freeing multiple contexts (%d)\n",
                               context->serial, context->major,
                               context->name_count, count);
                }
                audit_free_names(context);
                audit_free_aux(context);
                kfree(context);
                context  = previous;
        } while (context);
        if (count >= 10)
                printk(KERN_ERR "audit: freed %d contexts\n", count);
}

static void audit_log_task_info(struct audit_buffer *ab)
{
        char name[sizeof(current->comm)];
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;

        get_task_comm(name, current);
        audit_log_format(ab, " comm=");
        audit_log_untrustedstring(ab, name);

        if (!mm)
                return;

        down_read(&mm->mmap_sem);
        vma = mm->mmap;
        while (vma) {
                if ((vma->vm_flags & VM_EXECUTABLE) &&
                    vma->vm_file) {
                        audit_log_d_path(ab, "exe=",
                                         vma->vm_file->f_dentry,
                                         vma->vm_file->f_vfsmnt);
                        break;
                }
                vma = vma->vm_next;
        }
        up_read(&mm->mmap_sem);
}

static void audit_log_exit(struct audit_context *context, gfp_t gfp_mask)
{
        int i;
        struct audit_buffer *ab;
        struct audit_aux_data *aux;

        ab = audit_log_start(context, gfp_mask, AUDIT_SYSCALL);
        if (!ab)
                return;         /* audit_panic has been called */
        audit_log_format(ab, "arch=%x syscall=%d",
                         context->arch, context->major);
        if (context->personality != PER_LINUX)
                audit_log_format(ab, " per=%lx", context->personality);
        if (context->return_valid)
                audit_log_format(ab, " success=%s exit=%ld", 
                                 (context->return_valid==AUDITSC_SUCCESS)?"yes":"no",
                                 context->return_code);
        audit_log_format(ab,
                  " a0=%lx a1=%lx a2=%lx a3=%lx items=%d"
                  " pid=%d auid=%u uid=%u gid=%u"
                  " euid=%u suid=%u fsuid=%u"
                  " egid=%u sgid=%u fsgid=%u",
                  context->argv[0],
                  context->argv[1],
                  context->argv[2],
                  context->argv[3],
                  context->name_count,
                  context->pid,
                  context->loginuid,
                  context->uid,
                  context->gid,
                  context->euid, context->suid, context->fsuid,
                  context->egid, context->sgid, context->fsgid);
        audit_log_task_info(ab);
        audit_log_end(ab);

        for (aux = context->aux; aux; aux = aux->next) {

                ab = audit_log_start(context, gfp_mask, aux->type);
                if (!ab)
                        continue; /* audit_panic has been called */

                switch (aux->type) {
                case AUDIT_IPC: {
                        struct audit_aux_data_ipcctl *axi = (void *)aux;
                        audit_log_format(ab, 
                                         " qbytes=%lx iuid=%u igid=%u mode=%x",
                                         axi->qbytes, axi->uid, axi->gid, axi->mode);
                        break; }

                case AUDIT_SOCKETCALL: {
                        int i;
                        struct audit_aux_data_socketcall *axs = (void *)aux;
                        audit_log_format(ab, "nargs=%d", axs->nargs);
                        for (i=0; i<axs->nargs; i++)
                                audit_log_format(ab, " a%d=%lx", i, axs->args[i]);
                        break; }

                case AUDIT_SOCKADDR: {
                        struct audit_aux_data_sockaddr *axs = (void *)aux;

                        audit_log_format(ab, "saddr=");
                        audit_log_hex(ab, axs->a, axs->len);
                        break; }

                case AUDIT_AVC_PATH: {
                        struct audit_aux_data_path *axi = (void *)aux;
                        audit_log_d_path(ab, "path=", axi->dentry, axi->mnt);
                        break; }

                }
                audit_log_end(ab);
        }

        if (context->pwd && context->pwdmnt) {
                ab = audit_log_start(context, gfp_mask, AUDIT_CWD);
                if (ab) {
                        audit_log_d_path(ab, "cwd=", context->pwd, context->pwdmnt);
                        audit_log_end(ab);
                }
        }
        for (i = 0; i < context->name_count; i++) {
                unsigned long ino  = context->names[i].ino;
                unsigned long pino = context->names[i].pino;

                ab = audit_log_start(context, gfp_mask, AUDIT_PATH);
                if (!ab)
                        continue; /* audit_panic has been called */

                audit_log_format(ab, "item=%d", i);

                audit_log_format(ab, " name=");
                if (context->names[i].name)
                        audit_log_untrustedstring(ab, context->names[i].name);
                else
                        audit_log_format(ab, "(null)");

                if (pino != (unsigned long)-1)
                        audit_log_format(ab, " parent=%lu",  pino);
                if (ino != (unsigned long)-1)
                        audit_log_format(ab, " inode=%lu",  ino);
                if ((pino != (unsigned long)-1) || (ino != (unsigned long)-1))
                        audit_log_format(ab, " dev=%02x:%02x mode=%#o" 
                                         " ouid=%u ogid=%u rdev=%02x:%02x", 
                                         MAJOR(context->names[i].dev), 
                                         MINOR(context->names[i].dev), 
                                         context->names[i].mode, 
                                         context->names[i].uid, 
                                         context->names[i].gid, 
                                         MAJOR(context->names[i].rdev), 
                                         MINOR(context->names[i].rdev));
                audit_log_end(ab);
        }
}

/**
 * audit_free - free a per-task audit context
 * @tsk: task whose audit context block to free
 *
 * Called from copy_process and __put_task_struct.
 */
void audit_free(struct task_struct *tsk)
{
        struct audit_context *context;

        task_lock(tsk);
        context = audit_get_context(tsk, 0, 0);
        task_unlock(tsk);

        if (likely(!context))
                return;

        /* Check for system calls that do not go through the exit
         * function (e.g., exit_group), then free context block. 
         * We use GFP_ATOMIC here because we might be doing this 
         * in the context of the idle thread */
        if (context->in_syscall && context->auditable)
                audit_log_exit(context, GFP_ATOMIC);

        audit_free_context(context);
}

/**
 * audit_syscall_entry - fill in an audit record at syscall entry
 * @tsk: task being audited
 * @arch: architecture type
 * @major: major syscall type (function)
 * @a1: additional syscall register 1
 * @a2: additional syscall register 2
 * @a3: additional syscall register 3
 * @a4: additional syscall register 4
 *
 * Fill in audit context at syscall entry.  This only happens if the
 * audit context was created when the task was created and the state or
 * filters demand the audit context be built.  If the state from the
 * per-task filter or from the per-syscall filter is AUDIT_RECORD_CONTEXT,
 * then the record will be written at syscall exit time (otherwise, it
 * will only be written if another part of the kernel requests that it
 * be written).
 */
void audit_syscall_entry(struct task_struct *tsk, int arch, int major,
                         unsigned long a1, unsigned long a2,
                         unsigned long a3, unsigned long a4)
{
        struct audit_context *context = tsk->audit_context;
        enum audit_state     state;

        BUG_ON(!context);

        /*
         * This happens only on certain architectures that make system
         * calls in kernel_thread via the entry.S interface, instead of
         * with direct calls.  (If you are porting to a new
         * architecture, hitting this condition can indicate that you
         * got the _exit/_leave calls backward in entry.S.)
         *
         * i386     no
         * x86_64   no
         * ppc64    yes (see arch/ppc64/kernel/misc.S)
         *
         * This also happens with vm86 emulation in a non-nested manner
         * (entries without exits), so this case must be caught.
         */
        if (context->in_syscall) {
                struct audit_context *newctx;

#if AUDIT_DEBUG
                printk(KERN_ERR
                       "audit(:%d) pid=%d in syscall=%d;"
                       " entering syscall=%d\n",
                       context->serial, tsk->pid, context->major, major);
#endif
                newctx = audit_alloc_context(context->state);
                if (newctx) {
                        newctx->previous   = context;
                        context            = newctx;
                        tsk->audit_context = newctx;
                } else  {
                        /* If we can't alloc a new context, the best we
                         * can do is to leak memory (any pending putname
                         * will be lost).  The only other alternative is
                         * to abandon auditing. */
                        audit_zero_context(context, context->state);
                }
        }
        BUG_ON(context->in_syscall || context->name_count);

        if (!audit_enabled)
                return;

        context->arch       = arch;
        context->major      = major;
        context->argv[0]    = a1;
        context->argv[1]    = a2;
        context->argv[2]    = a3;
        context->argv[3]    = a4;

        state = context->state;
        if (state == AUDIT_SETUP_CONTEXT || state == AUDIT_BUILD_CONTEXT)
                state = audit_filter_syscall(tsk, context, &audit_filter_list[AUDIT_FILTER_ENTRY]);
        if (likely(state == AUDIT_DISABLED))
                return;

        context->serial     = 0;
        context->ctime      = CURRENT_TIME;
        context->in_syscall = 1;
        context->auditable  = !!(state == AUDIT_RECORD_CONTEXT);
}

/**
 * audit_syscall_exit - deallocate audit context after a system call
 * @tsk: task being audited
 * @valid: success/failure flag
 * @return_code: syscall return value
 *
 * Tear down after system call.  If the audit context has been marked as
 * auditable (either because of the AUDIT_RECORD_CONTEXT state from
 * filtering, or because some other part of the kernel write an audit
 * message), then write out the syscall information.  In call cases,
 * free the names stored from getname().
 */
void audit_syscall_exit(struct task_struct *tsk, int valid, long return_code)
{
        struct audit_context *context;

        get_task_struct(tsk);
        task_lock(tsk);
        context = audit_get_context(tsk, valid, return_code);
        task_unlock(tsk);

        /* Not having a context here is ok, since the parent may have
         * called __put_task_struct. */
        if (likely(!context))
                goto out;

        if (context->in_syscall && context->auditable)
                audit_log_exit(context, GFP_KERNEL);

        context->in_syscall = 0;
        context->auditable  = 0;

        if (context->previous) {
                struct audit_context *new_context = context->previous;
                context->previous  = NULL;
                audit_free_context(context);
                tsk->audit_context = new_context;
        } else {
                audit_free_names(context);
                audit_free_aux(context);
                tsk->audit_context = context;
        }
 out:
        put_task_struct(tsk);
}

/**
 * audit_getname - add a name to the list
 * @name: name to add
 *
 * Add a name to the list of audit names for this context.
 * Called from fs/namei.c:getname().
 */
void audit_getname(const char *name)
{
        struct audit_context *context = current->audit_context;

        if (!context || IS_ERR(name) || !name)
                return;

        if (!context->in_syscall) {
#if AUDIT_DEBUG == 2
                printk(KERN_ERR "%s:%d(:%d): ignoring getname(%p)\n",
                       __FILE__, __LINE__, context->serial, name);
                dump_stack();
#endif
                return;
        }
        BUG_ON(context->name_count >= AUDIT_NAMES);
        context->names[context->name_count].name = name;
        context->names[context->name_count].ino  = (unsigned long)-1;
        ++context->name_count;
        if (!context->pwd) {
                read_lock(&current->fs->lock);
                context->pwd = dget(current->fs->pwd);
                context->pwdmnt = mntget(current->fs->pwdmnt);
                read_unlock(&current->fs->lock);
        }
                
}

/* audit_putname - intercept a putname request
 * @name: name to intercept and delay for putname
 *
 * If we have stored the name from getname in the audit context,
 * then we delay the putname until syscall exit.
 * Called from include/linux/fs.h:putname().
 */
void audit_putname(const char *name)
{
        struct audit_context *context = current->audit_context;

        BUG_ON(!context);
        if (!context->in_syscall) {
#if AUDIT_DEBUG == 2
                printk(KERN_ERR "%s:%d(:%d): __putname(%p)\n",
                       __FILE__, __LINE__, context->serial, name);
                if (context->name_count) {
                        int i;
                        for (i = 0; i < context->name_count; i++)
                                printk(KERN_ERR "name[%d] = %p = %s\n", i,
                                       context->names[i].name,
                                       context->names[i].name ?: "(null)");
                }
#endif
                __putname(name);
        }
#if AUDIT_DEBUG
        else {
                ++context->put_count;
                if (context->put_count > context->name_count) {
                        printk(KERN_ERR "%s:%d(:%d): major=%d"
                               " in_syscall=%d putname(%p) name_count=%d"
                               " put_count=%d\n",
                               __FILE__, __LINE__,
                               context->serial, context->major,
                               context->in_syscall, name, context->name_count,
                               context->put_count);
                        dump_stack();
                }
        }
#endif
}

/**
 * audit_inode - store the inode and device from a lookup
 * @name: name being audited
 * @inode: inode being audited
 * @flags: lookup flags (as used in path_lookup())
 *
 * Called from fs/namei.c:path_lookup().
 */
void __audit_inode(const char *name, const struct inode *inode, unsigned flags)
{
        int idx;
        struct audit_context *context = current->audit_context;

        if (!context->in_syscall)
                return;
        if (context->name_count
            && context->names[context->name_count-1].name
            && context->names[context->name_count-1].name == name)
                idx = context->name_count - 1;
        else if (context->name_count > 1
                 && context->names[context->name_count-2].name
                 && context->names[context->name_count-2].name == name)
                idx = context->name_count - 2;
        else {
                /* FIXME: how much do we care about inodes that have no
                 * associated name? */
                if (context->name_count >= AUDIT_NAMES - AUDIT_NAMES_RESERVED)
                        return;
                idx = context->name_count++;
                context->names[idx].name = NULL;
#if AUDIT_DEBUG
                ++context->ino_count;
#endif
        }
        context->names[idx].dev   = inode->i_sb->s_dev;
        context->names[idx].mode  = inode->i_mode;
        context->names[idx].uid   = inode->i_uid;
        context->names[idx].gid   = inode->i_gid;
        context->names[idx].rdev  = inode->i_rdev;
        if ((flags & LOOKUP_PARENT) && (strcmp(name, "/") != 0) && 
            (strcmp(name, ".") != 0)) {
                context->names[idx].ino   = (unsigned long)-1;
                context->names[idx].pino  = inode->i_ino;
        } else {
                context->names[idx].ino   = inode->i_ino;
                context->names[idx].pino  = (unsigned long)-1;
        }
}

/**
 * audit_inode_child - collect inode info for created/removed objects
 * @dname: inode's dentry name
 * @inode: inode being audited
 * @pino: inode number of dentry parent
 *
 * For syscalls that create or remove filesystem objects, audit_inode
 * can only collect information for the filesystem object's parent.
 * This call updates the audit context with the child's information.
 * Syscalls that create a new filesystem object must be hooked after
 * the object is created.  Syscalls that remove a filesystem object
 * must be hooked prior, in order to capture the target inode during
 * unsuccessful attempts.
 */
void __audit_inode_child(const char *dname, const struct inode *inode,
                         unsigned long pino)
{
        int idx;
        struct audit_context *context = current->audit_context;

        if (!context->in_syscall)
                return;

        /* determine matching parent */
        if (dname)
                for (idx = 0; idx < context->name_count; idx++)
                        if (context->names[idx].pino == pino) {
                                const char *n;
                                const char *name = context->names[idx].name;
                                int dlen = strlen(dname);
                                int nlen = name ? strlen(name) : 0;

                                if (nlen < dlen)
                                        continue;
                                
                                /* disregard trailing slashes */
                                n = name + nlen - 1;
                                while ((*n == '/') && (n > name))
                                        n--;

                                /* find last path component */
                                n = n - dlen + 1;
                                if (n < name)
                                        continue;
                                else if (n > name) {
                                        if (*--n != '/')
                                                continue;
                                        else
                                                n++;
                                }

                                if (strncmp(n, dname, dlen) == 0)
                                        goto update_context;
                        }

        /* catch-all in case match not found */
        idx = context->name_count++;
        context->names[idx].name  = NULL;
        context->names[idx].pino  = pino;
#if AUDIT_DEBUG
        context->ino_count++;
#endif

update_context:
        if (inode) {
                context->names[idx].ino   = inode->i_ino;
                context->names[idx].dev   = inode->i_sb->s_dev;
                context->names[idx].mode  = inode->i_mode;
                context->names[idx].uid   = inode->i_uid;
                context->names[idx].gid   = inode->i_gid;
                context->names[idx].rdev  = inode->i_rdev;
        }
}

/**
 * auditsc_get_stamp - get local copies of audit_context values
 * @ctx: audit_context for the task
 * @t: timespec to store time recorded in the audit_context
 * @serial: serial value that is recorded in the audit_context
 *
 * Also sets the context as auditable.
 */
void auditsc_get_stamp(struct audit_context *ctx,
                       struct timespec *t, unsigned int *serial)
{
        if (!ctx->serial)
                ctx->serial = audit_serial();
        t->tv_sec  = ctx->ctime.tv_sec;
        t->tv_nsec = ctx->ctime.tv_nsec;
        *serial    = ctx->serial;
        ctx->auditable = 1;
}

/**
 * audit_set_loginuid - set a task's audit_context loginuid
 * @task: task whose audit context is being modified
 * @loginuid: loginuid value
 *
 * Returns 0.
 *
 * Called (set) from fs/proc/base.c::proc_loginuid_write().
 */
int audit_set_loginuid(struct task_struct *task, uid_t loginuid)
{
        if (task->audit_context) {
                struct audit_buffer *ab;

                ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
                if (ab) {
                        audit_log_format(ab, "login pid=%d uid=%u "
                                "old auid=%u new auid=%u",
                                task->pid, task->uid, 
                                task->audit_context->loginuid, loginuid);
                        audit_log_end(ab);
                }
                task->audit_context->loginuid = loginuid;
        }
        return 0;
}

/**
 * audit_get_loginuid - get the loginuid for an audit_context
 * @ctx: the audit_context
 *
 * Returns the context's loginuid or -1 if @ctx is NULL.
 */
uid_t audit_get_loginuid(struct audit_context *ctx)
{
        return ctx ? ctx->loginuid : -1;
}

/**
 * audit_ipc_perms - record audit data for ipc
 * @qbytes: msgq bytes
 * @uid: msgq user id
 * @gid: msgq group id
 * @mode: msgq mode (permissions)
 *
 * Returns 0 for success or NULL context or < 0 on error.
 */
int audit_ipc_perms(unsigned long qbytes, uid_t uid, gid_t gid, mode_t mode)
{
        struct audit_aux_data_ipcctl *ax;
        struct audit_context *context = current->audit_context;

        if (likely(!context))
                return 0;

        ax = kmalloc(sizeof(*ax), GFP_KERNEL);
        if (!ax)
                return -ENOMEM;

        ax->qbytes = qbytes;
        ax->uid = uid;
        ax->gid = gid;
        ax->mode = mode;

        ax->d.type = AUDIT_IPC;
        ax->d.next = context->aux;
        context->aux = (void *)ax;
        return 0;
}

/**
 * audit_socketcall - record audit data for sys_socketcall
 * @nargs: number of args
 * @args: args array
 *
 * Returns 0 for success or NULL context or < 0 on error.
 */
int audit_socketcall(int nargs, unsigned long *args)
{
        struct audit_aux_data_socketcall *ax;
        struct audit_context *context = current->audit_context;

        if (likely(!context))
                return 0;

        ax = kmalloc(sizeof(*ax) + nargs * sizeof(unsigned long), GFP_KERNEL);
        if (!ax)
                return -ENOMEM;

        ax->nargs = nargs;
        memcpy(ax->args, args, nargs * sizeof(unsigned long));

        ax->d.type = AUDIT_SOCKETCALL;
        ax->d.next = context->aux;
        context->aux = (void *)ax;
        return 0;
}

/**
 * audit_sockaddr - record audit data for sys_bind, sys_connect, sys_sendto
 * @len: data length in user space
 * @a: data address in kernel space
 *
 * Returns 0 for success or NULL context or < 0 on error.
 */
int audit_sockaddr(int len, void *a)
{
        struct audit_aux_data_sockaddr *ax;
        struct audit_context *context = current->audit_context;

        if (likely(!context))
                return 0;

        ax = kmalloc(sizeof(*ax) + len, GFP_KERNEL);
        if (!ax)
                return -ENOMEM;

        ax->len = len;
        memcpy(ax->a, a, len);

        ax->d.type = AUDIT_SOCKADDR;
        ax->d.next = context->aux;
        context->aux = (void *)ax;
        return 0;
}

/**
 * audit_avc_path - record the granting or denial of permissions
 * @dentry: dentry to record
 * @mnt: mnt to record
 *
 * Returns 0 for success or NULL context or < 0 on error.
 *
 * Called from security/selinux/avc.c::avc_audit()
 */
int audit_avc_path(struct dentry *dentry, struct vfsmount *mnt)
{
        struct audit_aux_data_path *ax;
        struct audit_context *context = current->audit_context;

        if (likely(!context))
                return 0;

        ax = kmalloc(sizeof(*ax), GFP_ATOMIC);
        if (!ax)
                return -ENOMEM;

        ax->dentry = dget(dentry);
        ax->mnt = mntget(mnt);

        ax->d.type = AUDIT_AVC_PATH;
        ax->d.next = context->aux;
        context->aux = (void *)ax;
        return 0;
}

/**
 * audit_signal_info - record signal info for shutting down audit subsystem
 * @sig: signal value
 * @t: task being signaled
 *
 * If the audit subsystem is being terminated, record the task (pid)
 * and uid that is doing that.
 */
void audit_signal_info(int sig, struct task_struct *t)
{
        extern pid_t audit_sig_pid;
        extern uid_t audit_sig_uid;

        if (unlikely(audit_pid && t->tgid == audit_pid)) {
                if (sig == SIGTERM || sig == SIGHUP) {
                        struct audit_context *ctx = current->audit_context;
                        audit_sig_pid = current->pid;
                        if (ctx)
                                audit_sig_uid = ctx->loginuid;
                        else
                                audit_sig_uid = current->uid;
                }
        }
}