auth_gss.c

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/*
 * linux/net/sunrpc/auth_gss/auth_gss.c
 *
 * RPCSEC_GSS client authentication.
 *
 *  Copyright (c) 2000 The Regents of the University of Michigan.
 *  All rights reserved.
 *
 *  Dug Song       <[email protected]>
 *  Andy Adamson   <[email protected]>
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. Neither the name of the University nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 *  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 *  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 *  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/pagemap.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/auth.h>
#include <linux/sunrpc/auth_gss.h>
#include <linux/sunrpc/svcauth_gss.h>
#include <linux/sunrpc/gss_err.h>
#include <linux/workqueue.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <linux/sunrpc/gss_api.h>
#include <asm/uaccess.h>

static const struct rpc_authops authgss_ops;

static const struct rpc_credops gss_credops;
static const struct rpc_credops gss_nullops;

#define GSS_RETRY_EXPIRED 5
static unsigned int gss_expired_cred_retry_delay = GSS_RETRY_EXPIRED;

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY    RPCDBG_AUTH
#endif

#define GSS_CRED_SLACK      (RPC_MAX_AUTH_SIZE * 2)
/* length of a krb5 verifier (48), plus data added before arguments when
 * using integrity (two 4-byte integers): */
#define GSS_VERF_SLACK      100

struct gss_auth {
    struct kref kref;
    struct rpc_auth rpc_auth;
    struct gss_api_mech *mech;
    enum rpc_gss_svc service;
    struct rpc_clnt *client;
    /*
     * There are two upcall pipes; dentry[1], named "gssd", is used
     * for the new text-based upcall; dentry[0] is named after the
     * mechanism (for example, "krb5") and exists for
     * backwards-compatibility with older gssd's.
     */
    struct rpc_pipe *pipe[2];
};

/* pipe_version >= 0 if and only if someone has a pipe open. */
static int pipe_version = -1;
static atomic_t pipe_users = ATOMIC_INIT(0);
static DEFINE_SPINLOCK(pipe_version_lock);
static struct rpc_wait_queue pipe_version_rpc_waitqueue;
static DECLARE_WAIT_QUEUE_HEAD(pipe_version_waitqueue);

static void gss_free_ctx(struct gss_cl_ctx *);
static const struct rpc_pipe_ops gss_upcall_ops_v0;
static const struct rpc_pipe_ops gss_upcall_ops_v1;

static inline struct gss_cl_ctx *
gss_get_ctx(struct gss_cl_ctx *ctx)
{
    atomic_inc(&ctx->count);
    return ctx;
}

static inline void
gss_put_ctx(struct gss_cl_ctx *ctx)
{
    if (atomic_dec_and_test(&ctx->count))
        gss_free_ctx(ctx);
}

/* gss_cred_set_ctx:
 * called by gss_upcall_callback and gss_create_upcall in order
 * to set the gss context. The actual exchange of an old context
 * and a new one is protected by the pipe->lock.
 */
static void
gss_cred_set_ctx(struct rpc_cred *cred, struct gss_cl_ctx *ctx)
{
    struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);

    if (!test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags))
        return;
    gss_get_ctx(ctx);
    rcu_assign_pointer(gss_cred->gc_ctx, ctx);
    set_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
    smp_mb__before_clear_bit();
    clear_bit(RPCAUTH_CRED_NEW, &cred->cr_flags);
}

static const void *
simple_get_bytes(const void *p, const void *end, void *res, size_t len)
{
    const void *q = (const void *)((const char *)p + len);
    if (unlikely(q > end || q < p))
        return ERR_PTR(-EFAULT);
    memcpy(res, p, len);
    return q;
}

static inline const void *
simple_get_netobj(const void *p, const void *end, struct xdr_netobj *dest)
{
    const void *q;
    unsigned int len;

    p = simple_get_bytes(p, end, &len, sizeof(len));
    if (IS_ERR(p))
        return p;
    q = (const void *)((const char *)p + len);
    if (unlikely(q > end || q < p))
        return ERR_PTR(-EFAULT);
    dest->data = kmemdup(p, len, GFP_NOFS);
    if (unlikely(dest->data == NULL))
        return ERR_PTR(-ENOMEM);
    dest->len = len;
    return q;
}

static struct gss_cl_ctx *
gss_cred_get_ctx(struct rpc_cred *cred)
{
    struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
    struct gss_cl_ctx *ctx = NULL;

    rcu_read_lock();
    if (gss_cred->gc_ctx)
        ctx = gss_get_ctx(gss_cred->gc_ctx);
    rcu_read_unlock();
    return ctx;
}

static struct gss_cl_ctx *
gss_alloc_context(void)
{
    struct gss_cl_ctx *ctx;

    ctx = kzalloc(sizeof(*ctx), GFP_NOFS);
    if (ctx != NULL) {
        ctx->gc_proc = RPC_GSS_PROC_DATA;
        ctx->gc_seq = 1;    /* NetApp 6.4R1 doesn't accept seq. no. 0 */
        spin_lock_init(&ctx->gc_seq_lock);
        atomic_set(&ctx->count,1);
    }
    return ctx;
}

#define GSSD_MIN_TIMEOUT (60 * 60)
static const void *
gss_fill_context(const void *p, const void *end, struct gss_cl_ctx *ctx, struct gss_api_mech *gm)
{
    const void *q;
    unsigned int seclen;
    unsigned int timeout;
    u32 window_size;
    int ret;

    /* First unsigned int gives the lifetime (in seconds) of the cred */
    p = simple_get_bytes(p, end, &timeout, sizeof(timeout));
    if (IS_ERR(p))
        goto err;
    if (timeout == 0)
        timeout = GSSD_MIN_TIMEOUT;
    ctx->gc_expiry = jiffies + (unsigned long)timeout * HZ * 3 / 4;
    /* Sequence number window. Determines the maximum number of simultaneous requests */
    p = simple_get_bytes(p, end, &window_size, sizeof(window_size));
    if (IS_ERR(p))
        goto err;
    ctx->gc_win = window_size;
    /* gssd signals an error by passing ctx->gc_win = 0: */
    if (ctx->gc_win == 0) {
        /*
         * in which case, p points to an error code. Anything other
         * than -EKEYEXPIRED gets converted to -EACCES.
         */
        p = simple_get_bytes(p, end, &ret, sizeof(ret));
        if (!IS_ERR(p))
            p = (ret == -EKEYEXPIRED) ? ERR_PTR(-EKEYEXPIRED) :
                            ERR_PTR(-EACCES);
        goto err;
    }
    /* copy the opaque wire context */
    p = simple_get_netobj(p, end, &ctx->gc_wire_ctx);
    if (IS_ERR(p))
        goto err;
    /* import the opaque security context */
    p  = simple_get_bytes(p, end, &seclen, sizeof(seclen));
    if (IS_ERR(p))
        goto err;
    q = (const void *)((const char *)p + seclen);
    if (unlikely(q > end || q < p)) {
        p = ERR_PTR(-EFAULT);
        goto err;
    }
    ret = gss_import_sec_context(p, seclen, gm, &ctx->gc_gss_ctx, GFP_NOFS);
    if (ret < 0) {
        p = ERR_PTR(ret);
        goto err;
    }
    return q;
err:
    dprintk("RPC:       %s returning %ld\n", __func__, -PTR_ERR(p));
    return p;
}

#define UPCALL_BUF_LEN 128

struct gss_upcall_msg {
    atomic_t count;
    uid_t   uid;
    struct rpc_pipe_msg msg;
    struct list_head list;
    struct gss_auth *auth;
    struct rpc_pipe *pipe;
    struct rpc_wait_queue rpc_waitqueue;
    wait_queue_head_t waitqueue;
    struct gss_cl_ctx *ctx;
    char databuf[UPCALL_BUF_LEN];
};

static int get_pipe_version(void)
{
    int ret;

    spin_lock(&pipe_version_lock);
    if (pipe_version >= 0) {
        atomic_inc(&pipe_users);
        ret = pipe_version;
    } else
        ret = -EAGAIN;
    spin_unlock(&pipe_version_lock);
    return ret;
}

static void put_pipe_version(void)
{
    if (atomic_dec_and_lock(&pipe_users, &pipe_version_lock)) {
        pipe_version = -1;
        spin_unlock(&pipe_version_lock);
    }
}

static void
gss_release_msg(struct gss_upcall_msg *gss_msg)
{
    if (!atomic_dec_and_test(&gss_msg->count))
        return;
    put_pipe_version();
    BUG_ON(!list_empty(&gss_msg->list));
    if (gss_msg->ctx != NULL)
        gss_put_ctx(gss_msg->ctx);
    rpc_destroy_wait_queue(&gss_msg->rpc_waitqueue);
    kfree(gss_msg);
}

static struct gss_upcall_msg *
__gss_find_upcall(struct rpc_pipe *pipe, uid_t uid)
{
    struct gss_upcall_msg *pos;
    list_for_each_entry(pos, &pipe->in_downcall, list) {
        if (pos->uid != uid)
            continue;
        atomic_inc(&pos->count);
        dprintk("RPC:       %s found msg %p\n", __func__, pos);
        return pos;
    }
    dprintk("RPC:       %s found nothing\n", __func__);
    return NULL;
}

/* Try to add an upcall to the pipefs queue.
 * If an upcall owned by our uid already exists, then we return a reference
 * to that upcall instead of adding the new upcall.
 */
static inline struct gss_upcall_msg *
gss_add_msg(struct gss_upcall_msg *gss_msg)
{
    struct rpc_pipe *pipe = gss_msg->pipe;
    struct gss_upcall_msg *old;

    spin_lock(&pipe->lock);
    old = __gss_find_upcall(pipe, gss_msg->uid);
    if (old == NULL) {
        atomic_inc(&gss_msg->count);
        list_add(&gss_msg->list, &pipe->in_downcall);
    } else
        gss_msg = old;
    spin_unlock(&pipe->lock);
    return gss_msg;
}

static void
__gss_unhash_msg(struct gss_upcall_msg *gss_msg)
{
    list_del_init(&gss_msg->list);
    rpc_wake_up_status(&gss_msg->rpc_waitqueue, gss_msg->msg.errno);
    wake_up_all(&gss_msg->waitqueue);
    atomic_dec(&gss_msg->count);
}

static void
gss_unhash_msg(struct gss_upcall_msg *gss_msg)
{
    struct rpc_pipe *pipe = gss_msg->pipe;

    if (list_empty(&gss_msg->list))
        return;
    spin_lock(&pipe->lock);
    if (!list_empty(&gss_msg->list))
        __gss_unhash_msg(gss_msg);
    spin_unlock(&pipe->lock);
}

static void
gss_handle_downcall_result(struct gss_cred *gss_cred, struct gss_upcall_msg *gss_msg)
{
    switch (gss_msg->msg.errno) {
    case 0:
        if (gss_msg->ctx == NULL)
            break;
        clear_bit(RPCAUTH_CRED_NEGATIVE, &gss_cred->gc_base.cr_flags);
        gss_cred_set_ctx(&gss_cred->gc_base, gss_msg->ctx);
        break;
    case -EKEYEXPIRED:
        set_bit(RPCAUTH_CRED_NEGATIVE, &gss_cred->gc_base.cr_flags);
    }
    gss_cred->gc_upcall_timestamp = jiffies;
    gss_cred->gc_upcall = NULL;
    rpc_wake_up_status(&gss_msg->rpc_waitqueue, gss_msg->msg.errno);
}

static void
gss_upcall_callback(struct rpc_task *task)
{
    struct gss_cred *gss_cred = container_of(task->tk_rqstp->rq_cred,
            struct gss_cred, gc_base);
    struct gss_upcall_msg *gss_msg = gss_cred->gc_upcall;
    struct rpc_pipe *pipe = gss_msg->pipe;

    spin_lock(&pipe->lock);
    gss_handle_downcall_result(gss_cred, gss_msg);
    spin_unlock(&pipe->lock);
    task->tk_status = gss_msg->msg.errno;
    gss_release_msg(gss_msg);
}

static void gss_encode_v0_msg(struct gss_upcall_msg *gss_msg)
{
    gss_msg->msg.data = &gss_msg->uid;
    gss_msg->msg.len = sizeof(gss_msg->uid);
}

static void gss_encode_v1_msg(struct gss_upcall_msg *gss_msg,
                struct rpc_clnt *clnt,
                const char *service_name)
{
    struct gss_api_mech *mech = gss_msg->auth->mech;
    char *p = gss_msg->databuf;
    int len = 0;

    gss_msg->msg.len = sprintf(gss_msg->databuf, "mech=%s uid=%d ",
                   mech->gm_name,
                   gss_msg->uid);
    p += gss_msg->msg.len;
    if (clnt->cl_principal) {
        len = sprintf(p, "target=%s ", clnt->cl_principal);
        p += len;
        gss_msg->msg.len += len;
    }
    if (service_name != NULL) {
        len = sprintf(p, "service=%s ", service_name);
        p += len;
        gss_msg->msg.len += len;
    }
    if (mech->gm_upcall_enctypes) {
        len = sprintf(p, "enctypes=%s ", mech->gm_upcall_enctypes);
        p += len;
        gss_msg->msg.len += len;
    }
    len = sprintf(p, "\n");
    gss_msg->msg.len += len;

    gss_msg->msg.data = gss_msg->databuf;
    BUG_ON(gss_msg->msg.len > UPCALL_BUF_LEN);
}

static void gss_encode_msg(struct gss_upcall_msg *gss_msg,
                struct rpc_clnt *clnt,
                const char *service_name)
{
    if (pipe_version == 0)
        gss_encode_v0_msg(gss_msg);
    else /* pipe_version == 1 */
        gss_encode_v1_msg(gss_msg, clnt, service_name);
}

static struct gss_upcall_msg *
gss_alloc_msg(struct gss_auth *gss_auth, struct rpc_clnt *clnt,
        uid_t uid, const char *service_name)
{
    struct gss_upcall_msg *gss_msg;
    int vers;

    gss_msg = kzalloc(sizeof(*gss_msg), GFP_NOFS);
    if (gss_msg == NULL)
        return ERR_PTR(-ENOMEM);
    vers = get_pipe_version();
    if (vers < 0) {
        kfree(gss_msg);
        return ERR_PTR(vers);
    }
    gss_msg->pipe = gss_auth->pipe[vers];
    INIT_LIST_HEAD(&gss_msg->list);
    rpc_init_wait_queue(&gss_msg->rpc_waitqueue, "RPCSEC_GSS upcall waitq");
    init_waitqueue_head(&gss_msg->waitqueue);
    atomic_set(&gss_msg->count, 1);
    gss_msg->uid = uid;
    gss_msg->auth = gss_auth;
    gss_encode_msg(gss_msg, clnt, service_name);
    return gss_msg;
}

static struct gss_upcall_msg *
gss_setup_upcall(struct rpc_clnt *clnt, struct gss_auth *gss_auth, struct rpc_cred *cred)
{
    struct gss_cred *gss_cred = container_of(cred,
            struct gss_cred, gc_base);
    struct gss_upcall_msg *gss_new, *gss_msg;
    uid_t uid = cred->cr_uid;

    gss_new = gss_alloc_msg(gss_auth, clnt, uid, gss_cred->gc_principal);
    if (IS_ERR(gss_new))
        return gss_new;
    gss_msg = gss_add_msg(gss_new);
    if (gss_msg == gss_new) {
        int res = rpc_queue_upcall(gss_new->pipe, &gss_new->msg);
        if (res) {
            gss_unhash_msg(gss_new);
            gss_msg = ERR_PTR(res);
        }
    } else
        gss_release_msg(gss_new);
    return gss_msg;
}

static void warn_gssd(void)
{
    static unsigned long ratelimit;
    unsigned long now = jiffies;

    if (time_after(now, ratelimit)) {
        printk(KERN_WARNING "RPC: AUTH_GSS upcall timed out.\n"
                "Please check user daemon is running.\n");
        ratelimit = now + 15*HZ;
    }
}

static inline int
gss_refresh_upcall(struct rpc_task *task)
{
    struct rpc_cred *cred = task->tk_rqstp->rq_cred;
    struct gss_auth *gss_auth = container_of(cred->cr_auth,
            struct gss_auth, rpc_auth);
    struct gss_cred *gss_cred = container_of(cred,
            struct gss_cred, gc_base);
    struct gss_upcall_msg *gss_msg;
    struct rpc_pipe *pipe;
    int err = 0;

    dprintk("RPC: %5u %s for uid %u\n",
        task->tk_pid, __func__, cred->cr_uid);
    gss_msg = gss_setup_upcall(task->tk_client, gss_auth, cred);
    if (PTR_ERR(gss_msg) == -EAGAIN) {
        /* XXX: warning on the first, under the assumption we
         * shouldn't normally hit this case on a refresh. */
        warn_gssd();
        task->tk_timeout = 15*HZ;
        rpc_sleep_on(&pipe_version_rpc_waitqueue, task, NULL);
        return -EAGAIN;
    }
    if (IS_ERR(gss_msg)) {
        err = PTR_ERR(gss_msg);
        goto out;
    }
    pipe = gss_msg->pipe;
    spin_lock(&pipe->lock);
    if (gss_cred->gc_upcall != NULL)
        rpc_sleep_on(&gss_cred->gc_upcall->rpc_waitqueue, task, NULL);
    else if (gss_msg->ctx == NULL && gss_msg->msg.errno >= 0) {
        task->tk_timeout = 0;
        gss_cred->gc_upcall = gss_msg;
        /* gss_upcall_callback will release the reference to gss_upcall_msg */
        atomic_inc(&gss_msg->count);
        rpc_sleep_on(&gss_msg->rpc_waitqueue, task, gss_upcall_callback);
    } else {
        gss_handle_downcall_result(gss_cred, gss_msg);
        err = gss_msg->msg.errno;
    }
    spin_unlock(&pipe->lock);
    gss_release_msg(gss_msg);
out:
    dprintk("RPC: %5u %s for uid %u result %d\n",
        task->tk_pid, __func__, cred->cr_uid, err);
    return err;
}

static inline int
gss_create_upcall(struct gss_auth *gss_auth, struct gss_cred *gss_cred)
{
    struct rpc_pipe *pipe;
    struct rpc_cred *cred = &gss_cred->gc_base;
    struct gss_upcall_msg *gss_msg;
    DEFINE_WAIT(wait);
    int err = 0;

    dprintk("RPC:       %s for uid %u\n", __func__, cred->cr_uid);
retry:
    gss_msg = gss_setup_upcall(gss_auth->client, gss_auth, cred);
    if (PTR_ERR(gss_msg) == -EAGAIN) {
        err = wait_event_interruptible_timeout(pipe_version_waitqueue,
                pipe_version >= 0, 15*HZ);
        if (pipe_version < 0) {
            warn_gssd();
            err = -EACCES;
        }
        if (err)
            goto out;
        goto retry;
    }
    if (IS_ERR(gss_msg)) {
        err = PTR_ERR(gss_msg);
        goto out;
    }
    pipe = gss_msg->pipe;
    for (;;) {
        prepare_to_wait(&gss_msg->waitqueue, &wait, TASK_KILLABLE);
        spin_lock(&pipe->lock);
        if (gss_msg->ctx != NULL || gss_msg->msg.errno < 0) {
            break;
        }
        spin_unlock(&pipe->lock);
        if (fatal_signal_pending(current)) {
            err = -ERESTARTSYS;
            goto out_intr;
        }
        schedule();
    }
    if (gss_msg->ctx)
        gss_cred_set_ctx(cred, gss_msg->ctx);
    else
        err = gss_msg->msg.errno;
    spin_unlock(&pipe->lock);
out_intr:
    finish_wait(&gss_msg->waitqueue, &wait);
    gss_release_msg(gss_msg);
out:
    dprintk("RPC:       %s for uid %u result %d\n",
        __func__, cred->cr_uid, err);
    return err;
}

#define MSG_BUF_MAXSIZE 1024

static ssize_t
gss_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
{
    const void *p, *end;
    void *buf;
    struct gss_upcall_msg *gss_msg;
    struct rpc_pipe *pipe = RPC_I(filp->f_dentry->d_inode)->pipe;
    struct gss_cl_ctx *ctx;
    uid_t uid;
    ssize_t err = -EFBIG;

    if (mlen > MSG_BUF_MAXSIZE)
        goto out;
    err = -ENOMEM;
    buf = kmalloc(mlen, GFP_NOFS);
    if (!buf)
        goto out;

    err = -EFAULT;
    if (copy_from_user(buf, src, mlen))
        goto err;

    end = (const void *)((char *)buf + mlen);
    p = simple_get_bytes(buf, end, &uid, sizeof(uid));
    if (IS_ERR(p)) {
        err = PTR_ERR(p);
        goto err;
    }

    err = -ENOMEM;
    ctx = gss_alloc_context();
    if (ctx == NULL)
        goto err;

    err = -ENOENT;
    /* Find a matching upcall */
    spin_lock(&pipe->lock);
    gss_msg = __gss_find_upcall(pipe, uid);
    if (gss_msg == NULL) {
        spin_unlock(&pipe->lock);
        goto err_put_ctx;
    }
    list_del_init(&gss_msg->list);
    spin_unlock(&pipe->lock);

    p = gss_fill_context(p, end, ctx, gss_msg->auth->mech);
    if (IS_ERR(p)) {
        err = PTR_ERR(p);
        switch (err) {
        case -EACCES:
        case -EKEYEXPIRED:
            gss_msg->msg.errno = err;
            err = mlen;
            break;
        case -EFAULT:
        case -ENOMEM:
        case -EINVAL:
        case -ENOSYS:
            gss_msg->msg.errno = -EAGAIN;
            break;
        default:
            printk(KERN_CRIT "%s: bad return from "
                "gss_fill_context: %zd\n", __func__, err);
            BUG();
        }
        goto err_release_msg;
    }
    gss_msg->ctx = gss_get_ctx(ctx);
    err = mlen;

err_release_msg:
    spin_lock(&pipe->lock);
    __gss_unhash_msg(gss_msg);
    spin_unlock(&pipe->lock);
    gss_release_msg(gss_msg);
err_put_ctx:
    gss_put_ctx(ctx);
err:
    kfree(buf);
out:
    dprintk("RPC:       %s returning %Zd\n", __func__, err);
    return err;
}

static int gss_pipe_open(struct inode *inode, int new_version)
{
    int ret = 0;

    spin_lock(&pipe_version_lock);
    if (pipe_version < 0) {
        /* First open of any gss pipe determines the version: */
        pipe_version = new_version;
        rpc_wake_up(&pipe_version_rpc_waitqueue);
        wake_up(&pipe_version_waitqueue);
    } else if (pipe_version != new_version) {
        /* Trying to open a pipe of a different version */
        ret = -EBUSY;
        goto out;
    }
    atomic_inc(&pipe_users);
out:
    spin_unlock(&pipe_version_lock);
    return ret;

}

static int gss_pipe_open_v0(struct inode *inode)
{
    return gss_pipe_open(inode, 0);
}

static int gss_pipe_open_v1(struct inode *inode)
{
    return gss_pipe_open(inode, 1);
}

static void
gss_pipe_release(struct inode *inode)
{
    struct rpc_pipe *pipe = RPC_I(inode)->pipe;
    struct gss_upcall_msg *gss_msg;

restart:
    spin_lock(&pipe->lock);
    list_for_each_entry(gss_msg, &pipe->in_downcall, list) {

        if (!list_empty(&gss_msg->msg.list))
            continue;
        gss_msg->msg.errno = -EPIPE;
        atomic_inc(&gss_msg->count);
        __gss_unhash_msg(gss_msg);
        spin_unlock(&pipe->lock);
        gss_release_msg(gss_msg);
        goto restart;
    }
    spin_unlock(&pipe->lock);

    put_pipe_version();
}

static void
gss_pipe_destroy_msg(struct rpc_pipe_msg *msg)
{
    struct gss_upcall_msg *gss_msg = container_of(msg, struct gss_upcall_msg, msg);

    if (msg->errno < 0) {
        dprintk("RPC:       %s releasing msg %p\n",
            __func__, gss_msg);
        atomic_inc(&gss_msg->count);
        gss_unhash_msg(gss_msg);
        if (msg->errno == -ETIMEDOUT)
            warn_gssd();
        gss_release_msg(gss_msg);
    }
}

static void gss_pipes_dentries_destroy(struct rpc_auth *auth)
{
    struct gss_auth *gss_auth;

    gss_auth = container_of(auth, struct gss_auth, rpc_auth);
    if (gss_auth->pipe[0]->dentry)
        rpc_unlink(gss_auth->pipe[0]->dentry);
    if (gss_auth->pipe[1]->dentry)
        rpc_unlink(gss_auth->pipe[1]->dentry);
}

static int gss_pipes_dentries_create(struct rpc_auth *auth)
{
    int err;
    struct gss_auth *gss_auth;
    struct rpc_clnt *clnt;

    gss_auth = container_of(auth, struct gss_auth, rpc_auth);
    clnt = gss_auth->client;

    gss_auth->pipe[1]->dentry = rpc_mkpipe_dentry(clnt->cl_dentry,
                              "gssd",
                              clnt, gss_auth->pipe[1]);
    if (IS_ERR(gss_auth->pipe[1]->dentry))
        return PTR_ERR(gss_auth->pipe[1]->dentry);
    gss_auth->pipe[0]->dentry = rpc_mkpipe_dentry(clnt->cl_dentry,
                              gss_auth->mech->gm_name,
                              clnt, gss_auth->pipe[0]);
    if (IS_ERR(gss_auth->pipe[0]->dentry)) {
        err = PTR_ERR(gss_auth->pipe[0]->dentry);
        goto err_unlink_pipe_1;
    }
    return 0;

err_unlink_pipe_1:
    rpc_unlink(gss_auth->pipe[1]->dentry);
    return err;
}

static void gss_pipes_dentries_destroy_net(struct rpc_clnt *clnt,
                       struct rpc_auth *auth)
{
    struct net *net = rpc_net_ns(clnt);
    struct super_block *sb;

    sb = rpc_get_sb_net(net);
    if (sb) {
        if (clnt->cl_dentry)
            gss_pipes_dentries_destroy(auth);
        rpc_put_sb_net(net);
    }
}

static int gss_pipes_dentries_create_net(struct rpc_clnt *clnt,
                     struct rpc_auth *auth)
{
    struct net *net = rpc_net_ns(clnt);
    struct super_block *sb;
    int err = 0;

    sb = rpc_get_sb_net(net);
    if (sb) {
        if (clnt->cl_dentry)
            err = gss_pipes_dentries_create(auth);
        rpc_put_sb_net(net);
    }
    return err;
}

/*
 * NOTE: we have the opportunity to use different
 * parameters based on the input flavor (which must be a pseudoflavor)
 */
static struct rpc_auth *
gss_create(struct rpc_clnt *clnt, rpc_authflavor_t flavor)
{
    struct gss_auth *gss_auth;
    struct rpc_auth * auth;
    int err = -ENOMEM; /* XXX? */

    dprintk("RPC:       creating GSS authenticator for client %p\n", clnt);

    if (!try_module_get(THIS_MODULE))
        return ERR_PTR(err);
    if (!(gss_auth = kmalloc(sizeof(*gss_auth), GFP_KERNEL)))
        goto out_dec;
    gss_auth->client = clnt;
    err = -EINVAL;
    gss_auth->mech = gss_mech_get_by_pseudoflavor(flavor);
    if (!gss_auth->mech) {
        printk(KERN_WARNING "%s: Pseudoflavor %d not found!\n",
                __func__, flavor);
        goto err_free;
    }
    gss_auth->service = gss_pseudoflavor_to_service(gss_auth->mech, flavor);
    if (gss_auth->service == 0)
        goto err_put_mech;
    auth = &gss_auth->rpc_auth;
    auth->au_cslack = GSS_CRED_SLACK >> 2;
    auth->au_rslack = GSS_VERF_SLACK >> 2;
    auth->au_ops = &authgss_ops;
    auth->au_flavor = flavor;
    atomic_set(&auth->au_count, 1);
    kref_init(&gss_auth->kref);

    /*
     * Note: if we created the old pipe first, then someone who
     * examined the directory at the right moment might conclude
     * that we supported only the old pipe.  So we instead create
     * the new pipe first.
     */
    gss_auth->pipe[1] = rpc_mkpipe_data(&gss_upcall_ops_v1,
                        RPC_PIPE_WAIT_FOR_OPEN);
    if (IS_ERR(gss_auth->pipe[1])) {
        err = PTR_ERR(gss_auth->pipe[1]);
        goto err_put_mech;
    }

    gss_auth->pipe[0] = rpc_mkpipe_data(&gss_upcall_ops_v0,
                        RPC_PIPE_WAIT_FOR_OPEN);
    if (IS_ERR(gss_auth->pipe[0])) {
        err = PTR_ERR(gss_auth->pipe[0]);
        goto err_destroy_pipe_1;
    }
    err = gss_pipes_dentries_create_net(clnt, auth);
    if (err)
        goto err_destroy_pipe_0;
    err = rpcauth_init_credcache(auth);
    if (err)
        goto err_unlink_pipes;

    return auth;
err_unlink_pipes:
    gss_pipes_dentries_destroy_net(clnt, auth);
err_destroy_pipe_0:
    rpc_destroy_pipe_data(gss_auth->pipe[0]);
err_destroy_pipe_1:
    rpc_destroy_pipe_data(gss_auth->pipe[1]);
err_put_mech:
    gss_mech_put(gss_auth->mech);
err_free:
    kfree(gss_auth);
out_dec:
    module_put(THIS_MODULE);
    return ERR_PTR(err);
}

static void
gss_free(struct gss_auth *gss_auth)
{
    gss_pipes_dentries_destroy_net(gss_auth->client, &gss_auth->rpc_auth);
    rpc_destroy_pipe_data(gss_auth->pipe[0]);
    rpc_destroy_pipe_data(gss_auth->pipe[1]);
    gss_mech_put(gss_auth->mech);

    kfree(gss_auth);
    module_put(THIS_MODULE);
}

static void
gss_free_callback(struct kref *kref)
{
    struct gss_auth *gss_auth = container_of(kref, struct gss_auth, kref);

    gss_free(gss_auth);
}

static void
gss_destroy(struct rpc_auth *auth)
{
    struct gss_auth *gss_auth;

    dprintk("RPC:       destroying GSS authenticator %p flavor %d\n",
            auth, auth->au_flavor);

    rpcauth_destroy_credcache(auth);

    gss_auth = container_of(auth, struct gss_auth, rpc_auth);
    kref_put(&gss_auth->kref, gss_free_callback);
}

/*
 * gss_destroying_context will cause the RPCSEC_GSS to send a NULL RPC call
 * to the server with the GSS control procedure field set to
 * RPC_GSS_PROC_DESTROY. This should normally cause the server to release
 * all RPCSEC_GSS state associated with that context.
 */
static int
gss_destroying_context(struct rpc_cred *cred)
{
    struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
    struct gss_auth *gss_auth = container_of(cred->cr_auth, struct gss_auth, rpc_auth);
    struct rpc_task *task;

    if (gss_cred->gc_ctx == NULL ||
        test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags) == 0)
        return 0;

    gss_cred->gc_ctx->gc_proc = RPC_GSS_PROC_DESTROY;
    cred->cr_ops = &gss_nullops;

    /* Take a reference to ensure the cred will be destroyed either
     * by the RPC call or by the put_rpccred() below */
    get_rpccred(cred);

    task = rpc_call_null(gss_auth->client, cred, RPC_TASK_ASYNC|RPC_TASK_SOFT);
    if (!IS_ERR(task))
        rpc_put_task(task);

    put_rpccred(cred);
    return 1;
}

/* gss_destroy_cred (and gss_free_ctx) are used to clean up after failure
 * to create a new cred or context, so they check that things have been
 * allocated before freeing them. */
static void
gss_do_free_ctx(struct gss_cl_ctx *ctx)
{
    dprintk("RPC:       %s\n", __func__);

    gss_delete_sec_context(&ctx->gc_gss_ctx);
    kfree(ctx->gc_wire_ctx.data);
    kfree(ctx);
}

static void
gss_free_ctx_callback(struct rcu_head *head)
{
    struct gss_cl_ctx *ctx = container_of(head, struct gss_cl_ctx, gc_rcu);
    gss_do_free_ctx(ctx);
}

static void
gss_free_ctx(struct gss_cl_ctx *ctx)
{
    call_rcu(&ctx->gc_rcu, gss_free_ctx_callback);
}

static void
gss_free_cred(struct gss_cred *gss_cred)
{
    dprintk("RPC:       %s cred=%p\n", __func__, gss_cred);
    kfree(gss_cred);
}

static void
gss_free_cred_callback(struct rcu_head *head)
{
    struct gss_cred *gss_cred = container_of(head, struct gss_cred, gc_base.cr_rcu);
    gss_free_cred(gss_cred);
}

static void
gss_destroy_nullcred(struct rpc_cred *cred)
{
    struct gss_cred *gss_cred = container_of(cred, struct gss_cred, gc_base);
    struct gss_auth *gss_auth = container_of(cred->cr_auth, struct gss_auth, rpc_auth);
    struct gss_cl_ctx *ctx = gss_cred->gc_ctx;

    RCU_INIT_POINTER(gss_cred->gc_ctx, NULL);
    call_rcu(&cred->cr_rcu, gss_free_cred_callback);
    if (ctx)
        gss_put_ctx(ctx);
    kref_put(&gss_auth->kref, gss_free_callback);
}

static void
gss_destroy_cred(struct rpc_cred *cred)
{

    if (gss_destroying_context(cred))
        return;
    gss_destroy_nullcred(cred);
}

/*
 * Lookup RPCSEC_GSS cred for the current process
 */
static struct rpc_cred *
gss_lookup_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
    return rpcauth_lookup_credcache(auth, acred, flags);
}

static struct rpc_cred *
gss_create_cred(struct rpc_auth *auth, struct auth_cred *acred, int flags)
{
    struct gss_auth *gss_auth = container_of(auth, struct gss_auth, rpc_auth);
    struct gss_cred *cred = NULL;
    int err = -ENOMEM;

    dprintk("RPC:       %s for uid %d, flavor %d\n",
        __func__, acred->uid, auth->au_flavor);

    if (!(cred = kzalloc(sizeof(*cred), GFP_NOFS)))
        goto out_err;

    rpcauth_init_cred(&cred->gc_base, acred, auth, &gss_credops);
    /*
     * Note: in order to force a call to call_refresh(), we deliberately
     * fail to flag the credential as RPCAUTH_CRED_UPTODATE.
     */
    cred->gc_base.cr_flags = 1UL << RPCAUTH_CRED_NEW;
    cred->gc_service = gss_auth->service;
    cred->gc_principal = NULL;
    if (acred->machine_cred)
        cred->gc_principal = acred->principal;
    kref_get(&gss_auth->kref);
    return &cred->gc_base;

out_err:
    dprintk("RPC:       %s failed with error %d\n", __func__, err);
    return ERR_PTR(err);
}

static int
gss_cred_init(struct rpc_auth *auth, struct rpc_cred *cred)
{
    struct gss_auth *gss_auth = container_of(auth, struct gss_auth, rpc_auth);
    struct gss_cred *gss_cred = container_of(cred,struct gss_cred, gc_base);
    int err;

    do {
        err = gss_create_upcall(gss_auth, gss_cred);
    } while (err == -EAGAIN);
    return err;
}

static int
gss_match(struct auth_cred *acred, struct rpc_cred *rc, int flags)
{
    struct gss_cred *gss_cred = container_of(rc, struct gss_cred, gc_base);

    if (test_bit(RPCAUTH_CRED_NEW, &rc->cr_flags))
        goto out;
    /* Don't match with creds that have expired. */
    if (time_after(jiffies, gss_cred->gc_ctx->gc_expiry))
        return 0;
    if (!test_bit(RPCAUTH_CRED_UPTODATE, &rc->cr_flags))
        return 0;
out:
    if (acred->principal != NULL) {
        if (gss_cred->gc_principal == NULL)
            return 0;
        return strcmp(acred->principal, gss_cred->gc_principal) == 0;
    }
    if (gss_cred->gc_principal != NULL)
        return 0;
    return rc->cr_uid == acred->uid;
}

/*
* Marshal credentials.
* Maybe we should keep a cached credential for performance reasons.
*/
static __be32 *
gss_marshal(struct rpc_task *task, __be32 *p)
{
    struct rpc_rqst *req = task->tk_rqstp;
    struct rpc_cred *cred = req->rq_cred;
    struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
                         gc_base);
    struct gss_cl_ctx   *ctx = gss_cred_get_ctx(cred);
    __be32      *cred_len;
    u32             maj_stat = 0;
    struct xdr_netobj mic;
    struct kvec iov;
    struct xdr_buf  verf_buf;

    dprintk("RPC: %5u %s\n", task->tk_pid, __func__);

    *p++ = htonl(RPC_AUTH_GSS);
    cred_len = p++;

    spin_lock(&ctx->gc_seq_lock);
    req->rq_seqno = ctx->gc_seq++;
    spin_unlock(&ctx->gc_seq_lock);

    *p++ = htonl((u32) RPC_GSS_VERSION);
    *p++ = htonl((u32) ctx->gc_proc);
    *p++ = htonl((u32) req->rq_seqno);
    *p++ = htonl((u32) gss_cred->gc_service);
    p = xdr_encode_netobj(p, &ctx->gc_wire_ctx);
    *cred_len = htonl((p - (cred_len + 1)) << 2);

    /* We compute the checksum for the verifier over the xdr-encoded bytes
     * starting with the xid and ending at the end of the credential: */
    iov.iov_base = xprt_skip_transport_header(task->tk_xprt,
                    req->rq_snd_buf.head[0].iov_base);
    iov.iov_len = (u8 *)p - (u8 *)iov.iov_base;
    xdr_buf_from_iov(&iov, &verf_buf);

    /* set verifier flavor*/
    *p++ = htonl(RPC_AUTH_GSS);

    mic.data = (u8 *)(p + 1);
    maj_stat = gss_get_mic(ctx->gc_gss_ctx, &verf_buf, &mic);
    if (maj_stat == GSS_S_CONTEXT_EXPIRED) {
        clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
    } else if (maj_stat != 0) {
        printk("gss_marshal: gss_get_mic FAILED (%d)\n", maj_stat);
        goto out_put_ctx;
    }
    p = xdr_encode_opaque(p, NULL, mic.len);
    gss_put_ctx(ctx);
    return p;
out_put_ctx:
    gss_put_ctx(ctx);
    return NULL;
}

static int gss_renew_cred(struct rpc_task *task)
{
    struct rpc_cred *oldcred = task->tk_rqstp->rq_cred;
    struct gss_cred *gss_cred = container_of(oldcred,
                         struct gss_cred,
                         gc_base);
    struct rpc_auth *auth = oldcred->cr_auth;
    struct auth_cred acred = {
        .uid = oldcred->cr_uid,
        .principal = gss_cred->gc_principal,
        .machine_cred = (gss_cred->gc_principal != NULL ? 1 : 0),
    };
    struct rpc_cred *new;

    new = gss_lookup_cred(auth, &acred, RPCAUTH_LOOKUP_NEW);
    if (IS_ERR(new))
        return PTR_ERR(new);
    task->tk_rqstp->rq_cred = new;
    put_rpccred(oldcred);
    return 0;
}

static int gss_cred_is_negative_entry(struct rpc_cred *cred)
{
    if (test_bit(RPCAUTH_CRED_NEGATIVE, &cred->cr_flags)) {
        unsigned long now = jiffies;
        unsigned long begin, expire;
        struct gss_cred *gss_cred; 

        gss_cred = container_of(cred, struct gss_cred, gc_base);
        begin = gss_cred->gc_upcall_timestamp;
        expire = begin + gss_expired_cred_retry_delay * HZ;

        if (time_in_range_open(now, begin, expire))
            return 1;
    }
    return 0;
}

/*
* Refresh credentials. XXX - finish
*/
static int
gss_refresh(struct rpc_task *task)
{
    struct rpc_cred *cred = task->tk_rqstp->rq_cred;
    int ret = 0;

    if (gss_cred_is_negative_entry(cred))
        return -EKEYEXPIRED;

    if (!test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags) &&
            !test_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags)) {
        ret = gss_renew_cred(task);
        if (ret < 0)
            goto out;
        cred = task->tk_rqstp->rq_cred;
    }

    if (test_bit(RPCAUTH_CRED_NEW, &cred->cr_flags))
        ret = gss_refresh_upcall(task);
out:
    return ret;
}

/* Dummy refresh routine: used only when destroying the context */
static int
gss_refresh_null(struct rpc_task *task)
{
    return -EACCES;
}

static __be32 *
gss_validate(struct rpc_task *task, __be32 *p)
{
    struct rpc_cred *cred = task->tk_rqstp->rq_cred;
    struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
    __be32      seq;
    struct kvec iov;
    struct xdr_buf  verf_buf;
    struct xdr_netobj mic;
    u32     flav,len;
    u32     maj_stat;

    dprintk("RPC: %5u %s\n", task->tk_pid, __func__);

    flav = ntohl(*p++);
    if ((len = ntohl(*p++)) > RPC_MAX_AUTH_SIZE)
        goto out_bad;
    if (flav != RPC_AUTH_GSS)
        goto out_bad;
    seq = htonl(task->tk_rqstp->rq_seqno);
    iov.iov_base = &seq;
    iov.iov_len = sizeof(seq);
    xdr_buf_from_iov(&iov, &verf_buf);
    mic.data = (u8 *)p;
    mic.len = len;

    maj_stat = gss_verify_mic(ctx->gc_gss_ctx, &verf_buf, &mic);
    if (maj_stat == GSS_S_CONTEXT_EXPIRED)
        clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
    if (maj_stat) {
        dprintk("RPC: %5u %s: gss_verify_mic returned error 0x%08x\n",
            task->tk_pid, __func__, maj_stat);
        goto out_bad;
    }
    /* We leave it to unwrap to calculate au_rslack. For now we just
     * calculate the length of the verifier: */
    cred->cr_auth->au_verfsize = XDR_QUADLEN(len) + 2;
    gss_put_ctx(ctx);
    dprintk("RPC: %5u %s: gss_verify_mic succeeded.\n",
            task->tk_pid, __func__);
    return p + XDR_QUADLEN(len);
out_bad:
    gss_put_ctx(ctx);
    dprintk("RPC: %5u %s failed.\n", task->tk_pid, __func__);
    return NULL;
}

static void gss_wrap_req_encode(kxdreproc_t encode, struct rpc_rqst *rqstp,
                __be32 *p, void *obj)
{
    struct xdr_stream xdr;

    xdr_init_encode(&xdr, &rqstp->rq_snd_buf, p);
    encode(rqstp, &xdr, obj);
}

static inline int
gss_wrap_req_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
           kxdreproc_t encode, struct rpc_rqst *rqstp,
           __be32 *p, void *obj)
{
    struct xdr_buf  *snd_buf = &rqstp->rq_snd_buf;
    struct xdr_buf  integ_buf;
    __be32          *integ_len = NULL;
    struct xdr_netobj mic;
    u32     offset;
    __be32      *q;
    struct kvec *iov;
    u32             maj_stat = 0;
    int     status = -EIO;

    integ_len = p++;
    offset = (u8 *)p - (u8 *)snd_buf->head[0].iov_base;
    *p++ = htonl(rqstp->rq_seqno);

    gss_wrap_req_encode(encode, rqstp, p, obj);

    if (xdr_buf_subsegment(snd_buf, &integ_buf,
                offset, snd_buf->len - offset))
        return status;
    *integ_len = htonl(integ_buf.len);

    /* guess whether we're in the head or the tail: */
    if (snd_buf->page_len || snd_buf->tail[0].iov_len)
        iov = snd_buf->tail;
    else
        iov = snd_buf->head;
    p = iov->iov_base + iov->iov_len;
    mic.data = (u8 *)(p + 1);

    maj_stat = gss_get_mic(ctx->gc_gss_ctx, &integ_buf, &mic);
    status = -EIO; /* XXX? */
    if (maj_stat == GSS_S_CONTEXT_EXPIRED)
        clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
    else if (maj_stat)
        return status;
    q = xdr_encode_opaque(p, NULL, mic.len);

    offset = (u8 *)q - (u8 *)p;
    iov->iov_len += offset;
    snd_buf->len += offset;
    return 0;
}

static void
priv_release_snd_buf(struct rpc_rqst *rqstp)
{
    int i;

    for (i=0; i < rqstp->rq_enc_pages_num; i++)
        __free_page(rqstp->rq_enc_pages[i]);
    kfree(rqstp->rq_enc_pages);
}

static int
alloc_enc_pages(struct rpc_rqst *rqstp)
{
    struct xdr_buf *snd_buf = &rqstp->rq_snd_buf;
    int first, last, i;

    if (snd_buf->page_len == 0) {
        rqstp->rq_enc_pages_num = 0;
        return 0;
    }

    first = snd_buf->page_base >> PAGE_CACHE_SHIFT;
    last = (snd_buf->page_base + snd_buf->page_len - 1) >> PAGE_CACHE_SHIFT;
    rqstp->rq_enc_pages_num = last - first + 1 + 1;
    rqstp->rq_enc_pages
        = kmalloc(rqstp->rq_enc_pages_num * sizeof(struct page *),
                GFP_NOFS);
    if (!rqstp->rq_enc_pages)
        goto out;
    for (i=0; i < rqstp->rq_enc_pages_num; i++) {
        rqstp->rq_enc_pages[i] = alloc_page(GFP_NOFS);
        if (rqstp->rq_enc_pages[i] == NULL)
            goto out_free;
    }
    rqstp->rq_release_snd_buf = priv_release_snd_buf;
    return 0;
out_free:
    rqstp->rq_enc_pages_num = i;
    priv_release_snd_buf(rqstp);
out:
    return -EAGAIN;
}

static inline int
gss_wrap_req_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
          kxdreproc_t encode, struct rpc_rqst *rqstp,
          __be32 *p, void *obj)
{
    struct xdr_buf  *snd_buf = &rqstp->rq_snd_buf;
    u32     offset;
    u32             maj_stat;
    int     status;
    __be32      *opaque_len;
    struct page **inpages;
    int     first;
    int     pad;
    struct kvec *iov;
    char        *tmp;

    opaque_len = p++;
    offset = (u8 *)p - (u8 *)snd_buf->head[0].iov_base;
    *p++ = htonl(rqstp->rq_seqno);

    gss_wrap_req_encode(encode, rqstp, p, obj);

    status = alloc_enc_pages(rqstp);
    if (status)
        return status;
    first = snd_buf->page_base >> PAGE_CACHE_SHIFT;
    inpages = snd_buf->pages + first;
    snd_buf->pages = rqstp->rq_enc_pages;
    snd_buf->page_base -= first << PAGE_CACHE_SHIFT;
    /*
     * Give the tail its own page, in case we need extra space in the
     * head when wrapping:
     *
     * call_allocate() allocates twice the slack space required
     * by the authentication flavor to rq_callsize.
     * For GSS, slack is GSS_CRED_SLACK.
     */
    if (snd_buf->page_len || snd_buf->tail[0].iov_len) {
        tmp = page_address(rqstp->rq_enc_pages[rqstp->rq_enc_pages_num - 1]);
        memcpy(tmp, snd_buf->tail[0].iov_base, snd_buf->tail[0].iov_len);
        snd_buf->tail[0].iov_base = tmp;
    }
    maj_stat = gss_wrap(ctx->gc_gss_ctx, offset, snd_buf, inpages);
    /* slack space should prevent this ever happening: */
    BUG_ON(snd_buf->len > snd_buf->buflen);
    status = -EIO;
    /* We're assuming that when GSS_S_CONTEXT_EXPIRED, the encryption was
     * done anyway, so it's safe to put the request on the wire: */
    if (maj_stat == GSS_S_CONTEXT_EXPIRED)
        clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
    else if (maj_stat)
        return status;

    *opaque_len = htonl(snd_buf->len - offset);
    /* guess whether we're in the head or the tail: */
    if (snd_buf->page_len || snd_buf->tail[0].iov_len)
        iov = snd_buf->tail;
    else
        iov = snd_buf->head;
    p = iov->iov_base + iov->iov_len;
    pad = 3 - ((snd_buf->len - offset - 1) & 3);
    memset(p, 0, pad);
    iov->iov_len += pad;
    snd_buf->len += pad;

    return 0;
}

static int
gss_wrap_req(struct rpc_task *task,
         kxdreproc_t encode, void *rqstp, __be32 *p, void *obj)
{
    struct rpc_cred *cred = task->tk_rqstp->rq_cred;
    struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
            gc_base);
    struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
    int             status = -EIO;

    dprintk("RPC: %5u %s\n", task->tk_pid, __func__);
    if (ctx->gc_proc != RPC_GSS_PROC_DATA) {
        /* The spec seems a little ambiguous here, but I think that not
         * wrapping context destruction requests makes the most sense.
         */
        gss_wrap_req_encode(encode, rqstp, p, obj);
        status = 0;
        goto out;
    }
    switch (gss_cred->gc_service) {
    case RPC_GSS_SVC_NONE:
        gss_wrap_req_encode(encode, rqstp, p, obj);
        status = 0;
        break;
    case RPC_GSS_SVC_INTEGRITY:
        status = gss_wrap_req_integ(cred, ctx, encode, rqstp, p, obj);
        break;
    case RPC_GSS_SVC_PRIVACY:
        status = gss_wrap_req_priv(cred, ctx, encode, rqstp, p, obj);
        break;
    }
out:
    gss_put_ctx(ctx);
    dprintk("RPC: %5u %s returning %d\n", task->tk_pid, __func__, status);
    return status;
}

static inline int
gss_unwrap_resp_integ(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
        struct rpc_rqst *rqstp, __be32 **p)
{
    struct xdr_buf  *rcv_buf = &rqstp->rq_rcv_buf;
    struct xdr_buf integ_buf;
    struct xdr_netobj mic;
    u32 data_offset, mic_offset;
    u32 integ_len;
    u32 maj_stat;
    int status = -EIO;

    integ_len = ntohl(*(*p)++);
    if (integ_len & 3)
        return status;
    data_offset = (u8 *)(*p) - (u8 *)rcv_buf->head[0].iov_base;
    mic_offset = integ_len + data_offset;
    if (mic_offset > rcv_buf->len)
        return status;
    if (ntohl(*(*p)++) != rqstp->rq_seqno)
        return status;

    if (xdr_buf_subsegment(rcv_buf, &integ_buf, data_offset,
                mic_offset - data_offset))
        return status;

    if (xdr_buf_read_netobj(rcv_buf, &mic, mic_offset))
        return status;

    maj_stat = gss_verify_mic(ctx->gc_gss_ctx, &integ_buf, &mic);
    if (maj_stat == GSS_S_CONTEXT_EXPIRED)
        clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
    if (maj_stat != GSS_S_COMPLETE)
        return status;
    return 0;
}

static inline int
gss_unwrap_resp_priv(struct rpc_cred *cred, struct gss_cl_ctx *ctx,
        struct rpc_rqst *rqstp, __be32 **p)
{
    struct xdr_buf  *rcv_buf = &rqstp->rq_rcv_buf;
    u32 offset;
    u32 opaque_len;
    u32 maj_stat;
    int status = -EIO;

    opaque_len = ntohl(*(*p)++);
    offset = (u8 *)(*p) - (u8 *)rcv_buf->head[0].iov_base;
    if (offset + opaque_len > rcv_buf->len)
        return status;
    /* remove padding: */
    rcv_buf->len = offset + opaque_len;

    maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset, rcv_buf);
    if (maj_stat == GSS_S_CONTEXT_EXPIRED)
        clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
    if (maj_stat != GSS_S_COMPLETE)
        return status;
    if (ntohl(*(*p)++) != rqstp->rq_seqno)
        return status;

    return 0;
}

static int
gss_unwrap_req_decode(kxdrdproc_t decode, struct rpc_rqst *rqstp,
              __be32 *p, void *obj)
{
    struct xdr_stream xdr;

    xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
    return decode(rqstp, &xdr, obj);
}

static int
gss_unwrap_resp(struct rpc_task *task,
        kxdrdproc_t decode, void *rqstp, __be32 *p, void *obj)
{
    struct rpc_cred *cred = task->tk_rqstp->rq_cred;
    struct gss_cred *gss_cred = container_of(cred, struct gss_cred,
            gc_base);
    struct gss_cl_ctx *ctx = gss_cred_get_ctx(cred);
    __be32      *savedp = p;
    struct kvec *head = ((struct rpc_rqst *)rqstp)->rq_rcv_buf.head;
    int     savedlen = head->iov_len;
    int             status = -EIO;

    if (ctx->gc_proc != RPC_GSS_PROC_DATA)
        goto out_decode;
    switch (gss_cred->gc_service) {
    case RPC_GSS_SVC_NONE:
        break;
    case RPC_GSS_SVC_INTEGRITY:
        status = gss_unwrap_resp_integ(cred, ctx, rqstp, &p);
        if (status)
            goto out;
        break;
    case RPC_GSS_SVC_PRIVACY:
        status = gss_unwrap_resp_priv(cred, ctx, rqstp, &p);
        if (status)
            goto out;
        break;
    }
    /* take into account extra slack for integrity and privacy cases: */
    cred->cr_auth->au_rslack = cred->cr_auth->au_verfsize + (p - savedp)
                        + (savedlen - head->iov_len);
out_decode:
    status = gss_unwrap_req_decode(decode, rqstp, p, obj);
out:
    gss_put_ctx(ctx);
    dprintk("RPC: %5u %s returning %d\n",
        task->tk_pid, __func__, status);
    return status;
}

static const struct rpc_authops authgss_ops = {
    .owner      = THIS_MODULE,
    .au_flavor  = RPC_AUTH_GSS,
    .au_name    = "RPCSEC_GSS",
    .create     = gss_create,
    .destroy    = gss_destroy,
    .lookup_cred    = gss_lookup_cred,
    .crcreate   = gss_create_cred,
    .pipes_create   = gss_pipes_dentries_create,
    .pipes_destroy  = gss_pipes_dentries_destroy,
    .list_pseudoflavors = gss_mech_list_pseudoflavors,
};

static const struct rpc_credops gss_credops = {
    .cr_name    = "AUTH_GSS",
    .crdestroy  = gss_destroy_cred,
    .cr_init    = gss_cred_init,
    .crbind     = rpcauth_generic_bind_cred,
    .crmatch    = gss_match,
    .crmarshal  = gss_marshal,
    .crrefresh  = gss_refresh,
    .crvalidate = gss_validate,
    .crwrap_req = gss_wrap_req,
    .crunwrap_resp  = gss_unwrap_resp,
};

static const struct rpc_credops gss_nullops = {
    .cr_name    = "AUTH_GSS",
    .crdestroy  = gss_destroy_nullcred,
    .crbind     = rpcauth_generic_bind_cred,
    .crmatch    = gss_match,
    .crmarshal  = gss_marshal,
    .crrefresh  = gss_refresh_null,
    .crvalidate = gss_validate,
    .crwrap_req = gss_wrap_req,
    .crunwrap_resp  = gss_unwrap_resp,
};

static const struct rpc_pipe_ops gss_upcall_ops_v0 = {
    .upcall     = rpc_pipe_generic_upcall,
    .downcall   = gss_pipe_downcall,
    .destroy_msg    = gss_pipe_destroy_msg,
    .open_pipe  = gss_pipe_open_v0,
    .release_pipe   = gss_pipe_release,
};

static const struct rpc_pipe_ops gss_upcall_ops_v1 = {
    .upcall     = rpc_pipe_generic_upcall,
    .downcall   = gss_pipe_downcall,
    .destroy_msg    = gss_pipe_destroy_msg,
    .open_pipe  = gss_pipe_open_v1,
    .release_pipe   = gss_pipe_release,
};

static __net_init int rpcsec_gss_init_net(struct net *net)
{
    return gss_svc_init_net(net);
}

static __net_exit void rpcsec_gss_exit_net(struct net *net)
{
    gss_svc_shutdown_net(net);
}

static struct pernet_operations rpcsec_gss_net_ops = {
    .init = rpcsec_gss_init_net,
    .exit = rpcsec_gss_exit_net,
};

/*
 * Initialize RPCSEC_GSS module
 */
static int __init init_rpcsec_gss(void)
{
    int err = 0;

    err = rpcauth_register(&authgss_ops);
    if (err)
        goto out;
    err = gss_svc_init();
    if (err)
        goto out_unregister;
    err = register_pernet_subsys(&rpcsec_gss_net_ops);
    if (err)
        goto out_svc_exit;
    rpc_init_wait_queue(&pipe_version_rpc_waitqueue, "gss pipe version");
    return 0;
out_svc_exit:
    gss_svc_shutdown();
out_unregister:
    rpcauth_unregister(&authgss_ops);
out:
    return err;
}

static void __exit exit_rpcsec_gss(void)
{
    unregister_pernet_subsys(&rpcsec_gss_net_ops);
    gss_svc_shutdown();
    rpcauth_unregister(&authgss_ops);
    rcu_barrier(); /* Wait for completion of call_rcu()'s */
}

MODULE_LICENSE("GPL");
module_param_named(expired_cred_retry_delay,
           gss_expired_cred_retry_delay,
           uint, 0644);
MODULE_PARM_DESC(expired_cred_retry_delay, "Timeout (in seconds) until "
        "the RPC engine retries an expired credential");

module_init(init_rpcsec_gss)
module_exit(exit_rpcsec_gss)