src/kernel/linux/v4.14/fs/nfs/callback_xdr.c

// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/nfs/callback_xdr.c
 *
 * Copyright (C) 2004 Trond Myklebust
 *
 * NFSv4 callback encode/decode procedures
 */
#include <linux/kernel.h>
#include <linux/sunrpc/svc.h>
#include <linux/nfs4.h>
#include <linux/nfs_fs.h>
#include <linux/ratelimit.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <linux/sunrpc/bc_xprt.h>
#include "nfs4_fs.h"
#include "callback.h"
#include "internal.h"
#include "nfs4session.h"

#define CB_OP_TAGLEN_MAXSZ		(512)
#define CB_OP_HDR_RES_MAXSZ		(2 * 4) // opcode, status
#define CB_OP_GETATTR_BITMAP_MAXSZ	(4 * 4) // bitmap length, 3 bitmaps
#define CB_OP_GETATTR_RES_MAXSZ		(CB_OP_HDR_RES_MAXSZ + \
					 CB_OP_GETATTR_BITMAP_MAXSZ + \
					 /* change, size, ctime, mtime */\
					 (2 + 2 + 3 + 3) * 4)
#define CB_OP_RECALL_RES_MAXSZ		(CB_OP_HDR_RES_MAXSZ)

#if defined(CONFIG_NFS_V4_1)
#define CB_OP_LAYOUTRECALL_RES_MAXSZ	(CB_OP_HDR_RES_MAXSZ)
#define CB_OP_DEVICENOTIFY_RES_MAXSZ	(CB_OP_HDR_RES_MAXSZ)
#define CB_OP_SEQUENCE_RES_MAXSZ	(CB_OP_HDR_RES_MAXSZ + \
					 NFS4_MAX_SESSIONID_LEN + \
					 (1 + 3) * 4) // seqid, 3 slotids
#define CB_OP_RECALLANY_RES_MAXSZ	(CB_OP_HDR_RES_MAXSZ)
#define CB_OP_RECALLSLOT_RES_MAXSZ	(CB_OP_HDR_RES_MAXSZ)
#define CB_OP_NOTIFY_LOCK_RES_MAXSZ	(CB_OP_HDR_RES_MAXSZ)
#endif /* CONFIG_NFS_V4_1 */

#define NFSDBG_FACILITY NFSDBG_CALLBACK

/* Internal error code */
#define NFS4ERR_RESOURCE_HDR	11050

struct callback_op {
	__be32 (*process_op)(void *, void *, struct cb_process_state *);
	__be32 (*decode_args)(struct svc_rqst *, struct xdr_stream *, void *);
	__be32 (*encode_res)(struct svc_rqst *, struct xdr_stream *,
			const void *);
	long res_maxsize;
};

static struct callback_op callback_ops[];

static __be32 nfs4_callback_null(struct svc_rqst *rqstp)
{
	return htonl(NFS4_OK);
}

static int nfs4_decode_void(struct svc_rqst *rqstp, __be32 *p)
{
	return xdr_argsize_check(rqstp, p);
}

static int nfs4_encode_void(struct svc_rqst *rqstp, __be32 *p)
{
	return xdr_ressize_check(rqstp, p);
}

static __be32 *read_buf(struct xdr_stream *xdr, size_t nbytes)
{
	__be32 *p;

	p = xdr_inline_decode(xdr, nbytes);
	if (unlikely(p == NULL))
		printk(KERN_WARNING "NFS: NFSv4 callback reply buffer overflowed!\n");
	return p;
}

static __be32 decode_string(struct xdr_stream *xdr, unsigned int *len,
		const char **str, size_t maxlen)
{
	ssize_t err;

	err = xdr_stream_decode_opaque_inline(xdr, (void **)str, maxlen);
	if (err < 0)
		return cpu_to_be32(NFS4ERR_RESOURCE);
	*len = err;
	return 0;
}

static __be32 decode_fh(struct xdr_stream *xdr, struct nfs_fh *fh)
{
	__be32 *p;

	p = read_buf(xdr, 4);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);
	fh->size = ntohl(*p);
	if (fh->size > NFS4_FHSIZE)
		return htonl(NFS4ERR_BADHANDLE);
	p = read_buf(xdr, fh->size);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);
	memcpy(&fh->data[0], p, fh->size);
	memset(&fh->data[fh->size], 0, sizeof(fh->data) - fh->size);
	return 0;
}

static __be32 decode_bitmap(struct xdr_stream *xdr, uint32_t *bitmap)
{
	__be32 *p;
	unsigned int attrlen;

	p = read_buf(xdr, 4);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);
	attrlen = ntohl(*p);
	p = read_buf(xdr, attrlen << 2);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);
	if (likely(attrlen > 0))
		bitmap[0] = ntohl(*p++);
	if (attrlen > 1)
		bitmap[1] = ntohl(*p);
	return 0;
}

static __be32 decode_stateid(struct xdr_stream *xdr, nfs4_stateid *stateid)
{
	__be32 *p;

	p = read_buf(xdr, NFS4_STATEID_SIZE);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);
	memcpy(stateid->data, p, NFS4_STATEID_SIZE);
	return 0;
}

static __be32 decode_delegation_stateid(struct xdr_stream *xdr, nfs4_stateid *stateid)
{
	stateid->type = NFS4_DELEGATION_STATEID_TYPE;
	return decode_stateid(xdr, stateid);
}

static __be32 decode_compound_hdr_arg(struct xdr_stream *xdr, struct cb_compound_hdr_arg *hdr)
{
	__be32 *p;
	__be32 status;

	status = decode_string(xdr, &hdr->taglen, &hdr->tag, CB_OP_TAGLEN_MAXSZ);
	if (unlikely(status != 0))
		return status;
	p = read_buf(xdr, 12);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);
	hdr->minorversion = ntohl(*p++);
	/* Check for minor version support */
	if (hdr->minorversion <= NFS4_MAX_MINOR_VERSION) {
		hdr->cb_ident = ntohl(*p++); /* ignored by v4.1 and v4.2 */
	} else {
		pr_warn_ratelimited("NFS: %s: NFSv4 server callback with "
			"illegal minor version %u!\n",
			__func__, hdr->minorversion);
		return htonl(NFS4ERR_MINOR_VERS_MISMATCH);
	}
	hdr->nops = ntohl(*p);
	return 0;
}

static __be32 decode_op_hdr(struct xdr_stream *xdr, unsigned int *op)
{
	__be32 *p;
	p = read_buf(xdr, 4);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE_HDR);
	*op = ntohl(*p);
	return 0;
}

static __be32 decode_getattr_args(struct svc_rqst *rqstp,
		struct xdr_stream *xdr, void *argp)
{
	struct cb_getattrargs *args = argp;
	__be32 status;

	status = decode_fh(xdr, &args->fh);
	if (unlikely(status != 0))
		return status;
	return decode_bitmap(xdr, args->bitmap);
}

static __be32 decode_recall_args(struct svc_rqst *rqstp,
		struct xdr_stream *xdr, void *argp)
{
	struct cb_recallargs *args = argp;
	__be32 *p;
	__be32 status;

	status = decode_delegation_stateid(xdr, &args->stateid);
	if (unlikely(status != 0))
		return status;
	p = read_buf(xdr, 4);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);
	args->truncate = ntohl(*p);
	return decode_fh(xdr, &args->fh);
}

#if defined(CONFIG_NFS_V4_1)
static __be32 decode_layout_stateid(struct xdr_stream *xdr, nfs4_stateid *stateid)
{
	stateid->type = NFS4_LAYOUT_STATEID_TYPE;
	return decode_stateid(xdr, stateid);
}

static __be32 decode_layoutrecall_args(struct svc_rqst *rqstp,
				       struct xdr_stream *xdr, void *argp)
{
	struct cb_layoutrecallargs *args = argp;
	__be32 *p;
	__be32 status = 0;
	uint32_t iomode;

	p = read_buf(xdr, 4 * sizeof(uint32_t));
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_BADXDR);

	args->cbl_layout_type = ntohl(*p++);
	/* Depite the spec's xdr, iomode really belongs in the FILE switch,
	 * as it is unusable and ignored with the other types.
	 */
	iomode = ntohl(*p++);
	args->cbl_layoutchanged = ntohl(*p++);
	args->cbl_recall_type = ntohl(*p++);

	if (args->cbl_recall_type == RETURN_FILE) {
		args->cbl_range.iomode = iomode;
		status = decode_fh(xdr, &args->cbl_fh);
		if (unlikely(status != 0))
			return status;

		p = read_buf(xdr, 2 * sizeof(uint64_t));
		if (unlikely(p == NULL))
			return htonl(NFS4ERR_BADXDR);
		p = xdr_decode_hyper(p, &args->cbl_range.offset);
		p = xdr_decode_hyper(p, &args->cbl_range.length);
		return decode_layout_stateid(xdr, &args->cbl_stateid);
	} else if (args->cbl_recall_type == RETURN_FSID) {
		p = read_buf(xdr, 2 * sizeof(uint64_t));
		if (unlikely(p == NULL))
			return htonl(NFS4ERR_BADXDR);
		p = xdr_decode_hyper(p, &args->cbl_fsid.major);
		p = xdr_decode_hyper(p, &args->cbl_fsid.minor);
	} else if (args->cbl_recall_type != RETURN_ALL)
		return htonl(NFS4ERR_BADXDR);
	return 0;
}

static
__be32 decode_devicenotify_args(struct svc_rqst *rqstp,
				struct xdr_stream *xdr,
				void *argp)
{
	struct cb_devicenotifyargs *args = argp;
	__be32 *p;
	__be32 status = 0;
	u32 tmp;
	int n, i;
	args->ndevs = 0;

	/* Num of device notifications */
	p = read_buf(xdr, sizeof(uint32_t));
	if (unlikely(p == NULL)) {
		status = htonl(NFS4ERR_BADXDR);
		goto out;
	}
	n = ntohl(*p++);
	if (n <= 0)
		goto out;
	if (n > ULONG_MAX / sizeof(*args->devs)) {
		status = htonl(NFS4ERR_BADXDR);
		goto out;
	}

	args->devs = kmalloc_array(n, sizeof(*args->devs), GFP_KERNEL);
	if (!args->devs) {
		status = htonl(NFS4ERR_DELAY);
		goto out;
	}

	/* Decode each dev notification */
	for (i = 0; i < n; i++) {
		struct cb_devicenotifyitem *dev = &args->devs[i];

		p = read_buf(xdr, (4 * sizeof(uint32_t)) + NFS4_DEVICEID4_SIZE);
		if (unlikely(p == NULL)) {
			status = htonl(NFS4ERR_BADXDR);
			goto err;
		}

		tmp = ntohl(*p++);	/* bitmap size */
		if (tmp != 1) {
			status = htonl(NFS4ERR_INVAL);
			goto err;
		}
		dev->cbd_notify_type = ntohl(*p++);
		if (dev->cbd_notify_type != NOTIFY_DEVICEID4_CHANGE &&
		    dev->cbd_notify_type != NOTIFY_DEVICEID4_DELETE) {
			status = htonl(NFS4ERR_INVAL);
			goto err;
		}

		tmp = ntohl(*p++);	/* opaque size */
		if (((dev->cbd_notify_type == NOTIFY_DEVICEID4_CHANGE) &&
		     (tmp != NFS4_DEVICEID4_SIZE + 8)) ||
		    ((dev->cbd_notify_type == NOTIFY_DEVICEID4_DELETE) &&
		     (tmp != NFS4_DEVICEID4_SIZE + 4))) {
			status = htonl(NFS4ERR_INVAL);
			goto err;
		}
		dev->cbd_layout_type = ntohl(*p++);
		memcpy(dev->cbd_dev_id.data, p, NFS4_DEVICEID4_SIZE);
		p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);

		if (dev->cbd_layout_type == NOTIFY_DEVICEID4_CHANGE) {
			p = read_buf(xdr, sizeof(uint32_t));
			if (unlikely(p == NULL)) {
				status = htonl(NFS4ERR_BADXDR);
				goto err;
			}
			dev->cbd_immediate = ntohl(*p++);
		} else {
			dev->cbd_immediate = 0;
		}

		args->ndevs++;

		dprintk("%s: type %d layout 0x%x immediate %d\n",
			__func__, dev->cbd_notify_type, dev->cbd_layout_type,
			dev->cbd_immediate);
	}
out:
	dprintk("%s: status %d ndevs %d\n",
		__func__, ntohl(status), args->ndevs);
	return status;
err:
	kfree(args->devs);
	goto out;
}

static __be32 decode_sessionid(struct xdr_stream *xdr,
				 struct nfs4_sessionid *sid)
{
	__be32 *p;

	p = read_buf(xdr, NFS4_MAX_SESSIONID_LEN);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);

	memcpy(sid->data, p, NFS4_MAX_SESSIONID_LEN);
	return 0;
}

static __be32 decode_rc_list(struct xdr_stream *xdr,
			       struct referring_call_list *rc_list)
{
	__be32 *p;
	int i;
	__be32 status;

	status = decode_sessionid(xdr, &rc_list->rcl_sessionid);
	if (status)
		goto out;

	status = htonl(NFS4ERR_RESOURCE);
	p = read_buf(xdr, sizeof(uint32_t));
	if (unlikely(p == NULL))
		goto out;

	rc_list->rcl_nrefcalls = ntohl(*p++);
	if (rc_list->rcl_nrefcalls) {
		p = read_buf(xdr,
			     rc_list->rcl_nrefcalls * 2 * sizeof(uint32_t));
		if (unlikely(p == NULL))
			goto out;
		rc_list->rcl_refcalls = kmalloc_array(rc_list->rcl_nrefcalls,
						sizeof(*rc_list->rcl_refcalls),
						GFP_KERNEL);
		if (unlikely(rc_list->rcl_refcalls == NULL))
			goto out;
		for (i = 0; i < rc_list->rcl_nrefcalls; i++) {
			rc_list->rcl_refcalls[i].rc_sequenceid = ntohl(*p++);
			rc_list->rcl_refcalls[i].rc_slotid = ntohl(*p++);
		}
	}
	status = 0;

out:
	return status;
}

static __be32 decode_cb_sequence_args(struct svc_rqst *rqstp,
					struct xdr_stream *xdr,
					void *argp)
{
	struct cb_sequenceargs *args = argp;
	__be32 *p;
	int i;
	__be32 status;

	status = decode_sessionid(xdr, &args->csa_sessionid);
	if (status)
		return status;

	p = read_buf(xdr, 5 * sizeof(uint32_t));
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);

	args->csa_addr = svc_addr(rqstp);
	args->csa_sequenceid = ntohl(*p++);
	args->csa_slotid = ntohl(*p++);
	args->csa_highestslotid = ntohl(*p++);
	args->csa_cachethis = ntohl(*p++);
	args->csa_nrclists = ntohl(*p++);
	args->csa_rclists = NULL;
	if (args->csa_nrclists) {
		args->csa_rclists = kmalloc_array(args->csa_nrclists,
						  sizeof(*args->csa_rclists),
						  GFP_KERNEL);
		if (unlikely(args->csa_rclists == NULL))
			return htonl(NFS4ERR_RESOURCE);

		for (i = 0; i < args->csa_nrclists; i++) {
			status = decode_rc_list(xdr, &args->csa_rclists[i]);
			if (status) {
				args->csa_nrclists = i;
				goto out_free;
			}
		}
	}
	return 0;

out_free:
	for (i = 0; i < args->csa_nrclists; i++)
		kfree(args->csa_rclists[i].rcl_refcalls);
	kfree(args->csa_rclists);
	return status;
}

static __be32 decode_recallany_args(struct svc_rqst *rqstp,
				      struct xdr_stream *xdr,
				      void *argp)
{
	struct cb_recallanyargs *args = argp;
	uint32_t bitmap[2];
	__be32 *p, status;

	p = read_buf(xdr, 4);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_BADXDR);
	args->craa_objs_to_keep = ntohl(*p++);
	status = decode_bitmap(xdr, bitmap);
	if (unlikely(status))
		return status;
	args->craa_type_mask = bitmap[0];

	return 0;
}

static __be32 decode_recallslot_args(struct svc_rqst *rqstp,
					struct xdr_stream *xdr,
					void *argp)
{
	struct cb_recallslotargs *args = argp;
	__be32 *p;

	p = read_buf(xdr, 4);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_BADXDR);
	args->crsa_target_highest_slotid = ntohl(*p++);
	return 0;
}

static __be32 decode_lockowner(struct xdr_stream *xdr, struct cb_notify_lock_args *args)
{
	__be32		*p;
	unsigned int	len;

	p = read_buf(xdr, 12);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_BADXDR);

	p = xdr_decode_hyper(p, &args->cbnl_owner.clientid);
	len = be32_to_cpu(*p);

	p = read_buf(xdr, len);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_BADXDR);

	/* Only try to decode if the length is right */
	if (len == 20) {
		p += 2;	/* skip "lock id:" */
		args->cbnl_owner.s_dev = be32_to_cpu(*p++);
		xdr_decode_hyper(p, &args->cbnl_owner.id);
		args->cbnl_valid = true;
	} else {
		args->cbnl_owner.s_dev = 0;
		args->cbnl_owner.id = 0;
		args->cbnl_valid = false;
	}
	return 0;
}

static __be32 decode_notify_lock_args(struct svc_rqst *rqstp,
		struct xdr_stream *xdr, void *argp)
{
	struct cb_notify_lock_args *args = argp;
	__be32 status;

	status = decode_fh(xdr, &args->cbnl_fh);
	if (unlikely(status != 0))
		return status;
	return decode_lockowner(xdr, args);
}

#endif /* CONFIG_NFS_V4_1 */

static __be32 encode_string(struct xdr_stream *xdr, unsigned int len, const char *str)
{
	if (unlikely(xdr_stream_encode_opaque(xdr, str, len) < 0))
		return cpu_to_be32(NFS4ERR_RESOURCE);
	return 0;
}

#define CB_SUPPORTED_ATTR0 (FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE)
#define CB_SUPPORTED_ATTR1 (FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY)
static __be32 encode_attr_bitmap(struct xdr_stream *xdr, const uint32_t *bitmap, __be32 **savep)
{
	__be32 bm[2];
	__be32 *p;

	bm[0] = htonl(bitmap[0] & CB_SUPPORTED_ATTR0);
	bm[1] = htonl(bitmap[1] & CB_SUPPORTED_ATTR1);
	if (bm[1] != 0) {
		p = xdr_reserve_space(xdr, 16);
		if (unlikely(p == NULL))
			return htonl(NFS4ERR_RESOURCE);
		*p++ = htonl(2);
		*p++ = bm[0];
		*p++ = bm[1];
	} else if (bm[0] != 0) {
		p = xdr_reserve_space(xdr, 12);
		if (unlikely(p == NULL))
			return htonl(NFS4ERR_RESOURCE);
		*p++ = htonl(1);
		*p++ = bm[0];
	} else {
		p = xdr_reserve_space(xdr, 8);
		if (unlikely(p == NULL))
			return htonl(NFS4ERR_RESOURCE);
		*p++ = htonl(0);
	}
	*savep = p;
	return 0;
}

static __be32 encode_attr_change(struct xdr_stream *xdr, const uint32_t *bitmap, uint64_t change)
{
	__be32 *p;

	if (!(bitmap[0] & FATTR4_WORD0_CHANGE))
		return 0;
	p = xdr_reserve_space(xdr, 8);
	if (unlikely(!p))
		return htonl(NFS4ERR_RESOURCE);
	p = xdr_encode_hyper(p, change);
	return 0;
}

static __be32 encode_attr_size(struct xdr_stream *xdr, const uint32_t *bitmap, uint64_t size)
{
	__be32 *p;

	if (!(bitmap[0] & FATTR4_WORD0_SIZE))
		return 0;
	p = xdr_reserve_space(xdr, 8);
	if (unlikely(!p))
		return htonl(NFS4ERR_RESOURCE);
	p = xdr_encode_hyper(p, size);
	return 0;
}

static __be32 encode_attr_time(struct xdr_stream *xdr, const struct timespec *time)
{
	__be32 *p;

	p = xdr_reserve_space(xdr, 12);
	if (unlikely(!p))
		return htonl(NFS4ERR_RESOURCE);
	p = xdr_encode_hyper(p, time->tv_sec);
	*p = htonl(time->tv_nsec);
	return 0;
}

static __be32 encode_attr_ctime(struct xdr_stream *xdr, const uint32_t *bitmap, const struct timespec *time)
{
	if (!(bitmap[1] & FATTR4_WORD1_TIME_METADATA))
		return 0;
	return encode_attr_time(xdr,time);
}

static __be32 encode_attr_mtime(struct xdr_stream *xdr, const uint32_t *bitmap, const struct timespec *time)
{
	if (!(bitmap[1] & FATTR4_WORD1_TIME_MODIFY))
		return 0;
	return encode_attr_time(xdr,time);
}

static __be32 encode_compound_hdr_res(struct xdr_stream *xdr, struct cb_compound_hdr_res *hdr)
{
	__be32 status;

	hdr->status = xdr_reserve_space(xdr, 4);
	if (unlikely(hdr->status == NULL))
		return htonl(NFS4ERR_RESOURCE);
	status = encode_string(xdr, hdr->taglen, hdr->tag);
	if (unlikely(status != 0))
		return status;
	hdr->nops = xdr_reserve_space(xdr, 4);
	if (unlikely(hdr->nops == NULL))
		return htonl(NFS4ERR_RESOURCE);
	return 0;
}

static __be32 encode_op_hdr(struct xdr_stream *xdr, uint32_t op, __be32 res)
{
	__be32 *p;
	
	p = xdr_reserve_space(xdr, 8);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE_HDR);
	*p++ = htonl(op);
	*p = res;
	return 0;
}

static __be32 encode_getattr_res(struct svc_rqst *rqstp, struct xdr_stream *xdr,
		const void *resp)
{
	const struct cb_getattrres *res = resp;
	__be32 *savep = NULL;
	__be32 status = res->status;
	
	if (unlikely(status != 0))
		goto out;
	status = encode_attr_bitmap(xdr, res->bitmap, &savep);
	if (unlikely(status != 0))
		goto out;
	status = encode_attr_change(xdr, res->bitmap, res->change_attr);
	if (unlikely(status != 0))
		goto out;
	status = encode_attr_size(xdr, res->bitmap, res->size);
	if (unlikely(status != 0))
		goto out;
	status = encode_attr_ctime(xdr, res->bitmap, &res->ctime);
	if (unlikely(status != 0))
		goto out;
	status = encode_attr_mtime(xdr, res->bitmap, &res->mtime);
	*savep = htonl((unsigned int)((char *)xdr->p - (char *)(savep+1)));
out:
	return status;
}

#if defined(CONFIG_NFS_V4_1)

static __be32 encode_sessionid(struct xdr_stream *xdr,
				 const struct nfs4_sessionid *sid)
{
	__be32 *p;

	p = xdr_reserve_space(xdr, NFS4_MAX_SESSIONID_LEN);
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);

	memcpy(p, sid, NFS4_MAX_SESSIONID_LEN);
	return 0;
}

static __be32 encode_cb_sequence_res(struct svc_rqst *rqstp,
				       struct xdr_stream *xdr,
				       const void *resp)
{
	const struct cb_sequenceres *res = resp;
	__be32 *p;
	__be32 status = res->csr_status;

	if (unlikely(status != 0))
		return status;

	status = encode_sessionid(xdr, &res->csr_sessionid);
	if (status)
		return status;

	p = xdr_reserve_space(xdr, 4 * sizeof(uint32_t));
	if (unlikely(p == NULL))
		return htonl(NFS4ERR_RESOURCE);

	*p++ = htonl(res->csr_sequenceid);
	*p++ = htonl(res->csr_slotid);
	*p++ = htonl(res->csr_highestslotid);
	*p++ = htonl(res->csr_target_highestslotid);
	return 0;
}

static __be32
preprocess_nfs41_op(int nop, unsigned int op_nr, struct callback_op **op)
{
	if (op_nr == OP_CB_SEQUENCE) {
		if (nop != 0)
			return htonl(NFS4ERR_SEQUENCE_POS);
	} else {
		if (nop == 0)
			return htonl(NFS4ERR_OP_NOT_IN_SESSION);
	}

	switch (op_nr) {
	case OP_CB_GETATTR:
	case OP_CB_RECALL:
	case OP_CB_SEQUENCE:
	case OP_CB_RECALL_ANY:
	case OP_CB_RECALL_SLOT:
	case OP_CB_LAYOUTRECALL:
	case OP_CB_NOTIFY_DEVICEID:
	case OP_CB_NOTIFY_LOCK:
		*op = &callback_ops[op_nr];
		break;

	case OP_CB_NOTIFY:
	case OP_CB_PUSH_DELEG:
	case OP_CB_RECALLABLE_OBJ_AVAIL:
	case OP_CB_WANTS_CANCELLED:
		return htonl(NFS4ERR_NOTSUPP);

	default:
		return htonl(NFS4ERR_OP_ILLEGAL);
	}

	return htonl(NFS_OK);
}

static void nfs4_callback_free_slot(struct nfs4_session *session,
		struct nfs4_slot *slot)
{
	struct nfs4_slot_table *tbl = &session->bc_slot_table;

	spin_lock(&tbl->slot_tbl_lock);
	/*
	 * Let the state manager know callback processing done.
	 * A single slot, so highest used slotid is either 0 or -1
	 */
	nfs4_free_slot(tbl, slot);
	spin_unlock(&tbl->slot_tbl_lock);
}

static void nfs4_cb_free_slot(struct cb_process_state *cps)
{
	if (cps->slot) {
		nfs4_callback_free_slot(cps->clp->cl_session, cps->slot);
		cps->slot = NULL;
	}
}

#else /* CONFIG_NFS_V4_1 */

static __be32
preprocess_nfs41_op(int nop, unsigned int op_nr, struct callback_op **op)
{
	return htonl(NFS4ERR_MINOR_VERS_MISMATCH);
}

static void nfs4_cb_free_slot(struct cb_process_state *cps)
{
}
#endif /* CONFIG_NFS_V4_1 */

#ifdef CONFIG_NFS_V4_2
static __be32
preprocess_nfs42_op(int nop, unsigned int op_nr, struct callback_op **op)
{
	__be32 status = preprocess_nfs41_op(nop, op_nr, op);
	if (status != htonl(NFS4ERR_OP_ILLEGAL))
		return status;

	if (op_nr == OP_CB_OFFLOAD)
		return htonl(NFS4ERR_NOTSUPP);
	return htonl(NFS4ERR_OP_ILLEGAL);
}
#else /* CONFIG_NFS_V4_2 */
static __be32
preprocess_nfs42_op(int nop, unsigned int op_nr, struct callback_op **op)
{
	return htonl(NFS4ERR_MINOR_VERS_MISMATCH);
}
#endif /* CONFIG_NFS_V4_2 */

static __be32
preprocess_nfs4_op(unsigned int op_nr, struct callback_op **op)
{
	switch (op_nr) {
	case OP_CB_GETATTR:
	case OP_CB_RECALL:
		*op = &callback_ops[op_nr];
		break;
	default:
		return htonl(NFS4ERR_OP_ILLEGAL);
	}

	return htonl(NFS_OK);
}

static __be32 process_op(int nop, struct svc_rqst *rqstp,
		struct xdr_stream *xdr_in, void *argp,
		struct xdr_stream *xdr_out, void *resp,
		struct cb_process_state *cps)
{
	struct callback_op *op = &callback_ops[0];
	unsigned int op_nr;
	__be32 status;
	long maxlen;
	__be32 res;

	status = decode_op_hdr(xdr_in, &op_nr);
	if (unlikely(status))
		return status;

	switch (cps->minorversion) {
	case 0:
		status = preprocess_nfs4_op(op_nr, &op);
		break;
	case 1:
		status = preprocess_nfs41_op(nop, op_nr, &op);
		break;
	case 2:
		status = preprocess_nfs42_op(nop, op_nr, &op);
		break;
	default:
		status = htonl(NFS4ERR_MINOR_VERS_MISMATCH);
	}

	if (status == htonl(NFS4ERR_OP_ILLEGAL))
		op_nr = OP_CB_ILLEGAL;
	if (status)
		goto encode_hdr;

	if (cps->drc_status) {
		status = cps->drc_status;
		goto encode_hdr;
	}

	maxlen = xdr_out->end - xdr_out->p;
	if (maxlen > 0 && maxlen < PAGE_SIZE) {
		status = op->decode_args(rqstp, xdr_in, argp);
		if (likely(status == 0))
			status = op->process_op(argp, resp, cps);
	} else
		status = htonl(NFS4ERR_RESOURCE);

encode_hdr:
	res = encode_op_hdr(xdr_out, op_nr, status);
	if (unlikely(res))
		return res;
	if (op->encode_res != NULL && status == 0)
		status = op->encode_res(rqstp, xdr_out, resp);
	return status;
}

/*
 * Decode, process and encode a COMPOUND
 */
static __be32 nfs4_callback_compound(struct svc_rqst *rqstp)
{
	struct cb_compound_hdr_arg hdr_arg = { 0 };
	struct cb_compound_hdr_res hdr_res = { NULL };
	struct xdr_stream xdr_in, xdr_out;
	__be32 *p, status;
	struct cb_process_state cps = {
		.drc_status = 0,
		.clp = NULL,
		.net = SVC_NET(rqstp),
	};
	unsigned int nops = 0;

	xdr_init_decode(&xdr_in, &rqstp->rq_arg, rqstp->rq_arg.head[0].iov_base);

	p = (__be32*)((char *)rqstp->rq_res.head[0].iov_base + rqstp->rq_res.head[0].iov_len);
	xdr_init_encode(&xdr_out, &rqstp->rq_res, p);

	status = decode_compound_hdr_arg(&xdr_in, &hdr_arg);
	if (status == htonl(NFS4ERR_RESOURCE))
		return rpc_garbage_args;

	if (hdr_arg.minorversion == 0) {
		cps.clp = nfs4_find_client_ident(SVC_NET(rqstp), hdr_arg.cb_ident);
		if (!cps.clp || !check_gss_callback_principal(cps.clp, rqstp)) {
			if (cps.clp)
				nfs_put_client(cps.clp);
			goto out_invalidcred;
		}
	}

	cps.minorversion = hdr_arg.minorversion;
	hdr_res.taglen = hdr_arg.taglen;
	hdr_res.tag = hdr_arg.tag;
	if (encode_compound_hdr_res(&xdr_out, &hdr_res) != 0) {
		if (cps.clp)
			nfs_put_client(cps.clp);
		return rpc_system_err;
	}
	while (status == 0 && nops != hdr_arg.nops) {
		status = process_op(nops, rqstp, &xdr_in,
				    rqstp->rq_argp, &xdr_out, rqstp->rq_resp,
				    &cps);
		nops++;
	}

	/* Buffer overflow in decode_ops_hdr or encode_ops_hdr. Return
	* resource error in cb_compound status without returning op */
	if (unlikely(status == htonl(NFS4ERR_RESOURCE_HDR))) {
		status = htonl(NFS4ERR_RESOURCE);
		nops--;
	}

	*hdr_res.status = status;
	*hdr_res.nops = htonl(nops);
	nfs4_cb_free_slot(&cps);
	nfs_put_client(cps.clp);
	return rpc_success;

out_invalidcred:
	pr_warn_ratelimited("NFS: NFSv4 callback contains invalid cred\n");
	return rpc_autherr_badcred;
}

/*
 * Define NFS4 callback COMPOUND ops.
 */
static struct callback_op callback_ops[] = {
	[0] = {
		.res_maxsize = CB_OP_HDR_RES_MAXSZ,
	},
	[OP_CB_GETATTR] = {
		.process_op = nfs4_callback_getattr,
		.decode_args = decode_getattr_args,
		.encode_res = encode_getattr_res,
		.res_maxsize = CB_OP_GETATTR_RES_MAXSZ,
	},
	[OP_CB_RECALL] = {
		.process_op = nfs4_callback_recall,
		.decode_args = decode_recall_args,
		.res_maxsize = CB_OP_RECALL_RES_MAXSZ,
	},
#if defined(CONFIG_NFS_V4_1)
	[OP_CB_LAYOUTRECALL] = {
		.process_op = nfs4_callback_layoutrecall,
		.decode_args = decode_layoutrecall_args,
		.res_maxsize = CB_OP_LAYOUTRECALL_RES_MAXSZ,
	},
	[OP_CB_NOTIFY_DEVICEID] = {
		.process_op = nfs4_callback_devicenotify,
		.decode_args = decode_devicenotify_args,
		.res_maxsize = CB_OP_DEVICENOTIFY_RES_MAXSZ,
	},
	[OP_CB_SEQUENCE] = {
		.process_op = nfs4_callback_sequence,
		.decode_args = decode_cb_sequence_args,
		.encode_res = encode_cb_sequence_res,
		.res_maxsize = CB_OP_SEQUENCE_RES_MAXSZ,
	},
	[OP_CB_RECALL_ANY] = {
		.process_op = nfs4_callback_recallany,
		.decode_args = decode_recallany_args,
		.res_maxsize = CB_OP_RECALLANY_RES_MAXSZ,
	},
	[OP_CB_RECALL_SLOT] = {
		.process_op = nfs4_callback_recallslot,
		.decode_args = decode_recallslot_args,
		.res_maxsize = CB_OP_RECALLSLOT_RES_MAXSZ,
	},
	[OP_CB_NOTIFY_LOCK] = {
		.process_op = nfs4_callback_notify_lock,
		.decode_args = decode_notify_lock_args,
		.res_maxsize = CB_OP_NOTIFY_LOCK_RES_MAXSZ,
	},
#endif /* CONFIG_NFS_V4_1 */
};

/*
 * Define NFS4 callback procedures
 */
static const struct svc_procedure nfs4_callback_procedures1[] = {
	[CB_NULL] = {
		.pc_func = nfs4_callback_null,
		.pc_decode = nfs4_decode_void,
		.pc_encode = nfs4_encode_void,
		.pc_xdrressize = 1,
	},
	[CB_COMPOUND] = {
		.pc_func = nfs4_callback_compound,
		.pc_encode = nfs4_encode_void,
		.pc_argsize = 256,
		.pc_ressize = 256,
		.pc_xdrressize = NFS4_CALLBACK_BUFSIZE,
	}
};

static unsigned int nfs4_callback_count1[ARRAY_SIZE(nfs4_callback_procedures1)];
const struct svc_version nfs4_callback_version1 = {
	.vs_vers = 1,
	.vs_nproc = ARRAY_SIZE(nfs4_callback_procedures1),
	.vs_proc = nfs4_callback_procedures1,
	.vs_count = nfs4_callback_count1,
	.vs_xdrsize = NFS4_CALLBACK_XDRSIZE,
	.vs_dispatch = NULL,
	.vs_hidden = true,
	.vs_need_cong_ctrl = true,
};

static unsigned int nfs4_callback_count4[ARRAY_SIZE(nfs4_callback_procedures1)];
const struct svc_version nfs4_callback_version4 = {
	.vs_vers = 4,
	.vs_nproc = ARRAY_SIZE(nfs4_callback_procedures1),
	.vs_proc = nfs4_callback_procedures1,
	.vs_count = nfs4_callback_count4,
	.vs_xdrsize = NFS4_CALLBACK_XDRSIZE,
	.vs_dispatch = NULL,
	.vs_hidden = true,
	.vs_need_cong_ctrl = true,
};