NSM: move to xdr_stream-based XDR encoders and decoders

Introduce xdr_stream-based XDR encoder and decoder functions, which are
more careful about preventing RPC buffer overflows.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/lockd/mon.c

@@ -193,21 +193,26 @@ nsm_create(void)
  * Status Monitor wire protocol.
  */
 
-static __be32 *xdr_encode_nsm_string(__be32 *p, char *string)
+static int encode_nsm_string(struct xdr_stream *xdr, const char *string)
 {
-	size_t len = strlen(string);
-
-	if (len > SM_MAXSTRLEN)
-		len = SM_MAXSTRLEN;
-	return xdr_encode_opaque(p, string, len);
+	const u32 len = strlen(string);
+	__be32 *p;
+
+	if (unlikely(len > SM_MAXSTRLEN))
+		return -EIO;
+	p = xdr_reserve_space(xdr, sizeof(u32) + len);
+	if (unlikely(p == NULL))
+		return -EIO;
+	xdr_encode_opaque(p, string, len);
+	return 0;
 }
 
 /*
  * "mon_name" specifies the host to be monitored.
  */
-static __be32 *xdr_encode_mon_name(__be32 *p, struct nsm_args *argp)
+static int encode_mon_name(struct xdr_stream *xdr, const struct nsm_args *argp)
 {
-	return xdr_encode_nsm_string(p, argp->mon_name);
+	return encode_nsm_string(xdr, argp->mon_name);
 }
 
 /*
@@ -216,30 +221,35 @@ static __be32 *xdr_encode_mon_name(__be32 *p, struct nsm_args *argp)
  * (via the NLMPROC_SM_NOTIFY call) that the state of host "mon_name"
  * has changed.
  */
-static __be32 *xdr_encode_my_id(__be32 *p, struct nsm_args *argp)
+static int encode_my_id(struct xdr_stream *xdr, const struct nsm_args *argp)
 {
-	p = xdr_encode_nsm_string(p, utsname()->nodename);
-	if (!p)
-		return ERR_PTR(-EIO);
-
+	int status;
+	__be32 *p;
+
+	status = encode_nsm_string(xdr, utsname()->nodename);
+	if (unlikely(status != 0))
+		return status;
+	p = xdr_reserve_space(xdr, 3 * sizeof(u32));
+	if (unlikely(p == NULL))
+		return -EIO;
 	*p++ = htonl(argp->prog);
 	*p++ = htonl(argp->vers);
 	*p++ = htonl(argp->proc);
-
-	return p;
+	return 0;
 }
 
 /*
  * The "mon_id" argument specifies the non-private arguments
  * of an NSMPROC_MON or NSMPROC_UNMON call.
  */
-static __be32 *xdr_encode_mon_id(__be32 *p, struct nsm_args *argp)
+static int encode_mon_id(struct xdr_stream *xdr, const struct nsm_args *argp)
 {
-	p = xdr_encode_mon_name(p, argp);
-	if (!p)
-		return ERR_PTR(-EIO);
+	int status;
 
-	return xdr_encode_my_id(p, argp);
+	status = encode_mon_name(xdr, argp);
+	if (unlikely(status != 0))
+		return status;
+	return encode_my_id(xdr, argp);
 }
 
 /*
@@ -250,55 +260,71 @@ static __be32 *xdr_encode_mon_id(__be32 *p, struct nsm_args *argp)
  * Linux provides the raw IP address of the monitored host,
  * left in network byte order.
  */
-static __be32 *xdr_encode_priv(__be32 *p, struct nsm_args *argp)
+static int encode_priv(struct xdr_stream *xdr, const struct nsm_args *argp)
 {
+	__be32 *p;
+
+	p = xdr_reserve_space(xdr, SM_PRIV_SIZE);
+	if (unlikely(p == NULL))
+		return -EIO;
 	*p++ = argp->addr;
 	*p++ = 0;
 	*p++ = 0;
 	*p++ = 0;
-
-	return p;
+	return 0;
 }
 
-static int
-xdr_encode_mon(struct rpc_rqst *rqstp, __be32 *p, struct nsm_args *argp)
+static int xdr_enc_mon(struct rpc_rqst *req, __be32 *p,
+		       const struct nsm_args *argp)
 {
-	p = xdr_encode_mon_id(p, argp);
-	if (IS_ERR(p))
-		return PTR_ERR(p);
-
-	p = xdr_encode_priv(p, argp);
-	if (IS_ERR(p))
-		return PTR_ERR(p);
+	struct xdr_stream xdr;
+	int status;
 
-	rqstp->rq_slen = xdr_adjust_iovec(rqstp->rq_svec, p);
-	return 0;
+	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
+	status = encode_mon_id(&xdr, argp);
+	if (unlikely(status))
+		return status;
+	return encode_priv(&xdr, argp);
 }
 
-static int
-xdr_encode_unmon(struct rpc_rqst *rqstp, __be32 *p, struct nsm_args *argp)
+static int xdr_enc_unmon(struct rpc_rqst *req, __be32 *p,
+			 const struct nsm_args *argp)
 {
-	p = xdr_encode_mon_id(p, argp);
-	if (IS_ERR(p))
-		return PTR_ERR(p);
-	rqstp->rq_slen = xdr_adjust_iovec(rqstp->rq_svec, p);
-	return 0;
+	struct xdr_stream xdr;
+
+	xdr_init_encode(&xdr, &req->rq_snd_buf, p);
+	return encode_mon_id(&xdr, argp);
 }
 
-static int
-xdr_decode_stat_res(struct rpc_rqst *rqstp, __be32 *p, struct nsm_res *resp)
+static int xdr_dec_stat_res(struct rpc_rqst *rqstp, __be32 *p,
+			    struct nsm_res *resp)
 {
+	struct xdr_stream xdr;
+
+	xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
+	p = xdr_inline_decode(&xdr, 2 * sizeof(u32));
+	if (unlikely(p == NULL))
+		return -EIO;
 	resp->status = ntohl(*p++);
-	resp->state = ntohl(*p++);
-	dprintk("nsm: xdr_decode_stat_res status %d state %d\n",
+	resp->state = ntohl(*p);
+
+	dprintk("lockd: xdr_dec_stat_res status %d state %d\n",
 			resp->status, resp->state);
 	return 0;
 }
 
-static int
-xdr_decode_stat(struct rpc_rqst *rqstp, __be32 *p, struct nsm_res *resp)
+static int xdr_dec_stat(struct rpc_rqst *rqstp, __be32 *p,
+			struct nsm_res *resp)
 {
-	resp->state = ntohl(*p++);
+	struct xdr_stream xdr;
+
+	xdr_init_decode(&xdr, &rqstp->rq_rcv_buf, p);
+	p = xdr_inline_decode(&xdr, sizeof(u32));
+	if (unlikely(p == NULL))
+		return -EIO;
+	resp->state = ntohl(*p);
+
+	dprintk("lockd: xdr_dec_stat state %d\n", resp->state);
 	return 0;
 }
 
@@ -314,8 +340,8 @@ xdr_decode_stat(struct rpc_rqst *rqstp, __be32 *p, struct nsm_res *resp)
 static struct rpc_procinfo	nsm_procedures[] = {
 [NSMPROC_MON] = {
 		.p_proc		= NSMPROC_MON,
-		.p_encode	= (kxdrproc_t) xdr_encode_mon,
-		.p_decode	= (kxdrproc_t) xdr_decode_stat_res,
+		.p_encode	= (kxdrproc_t)xdr_enc_mon,
+		.p_decode	= (kxdrproc_t)xdr_dec_stat_res,
 		.p_arglen	= SM_mon_sz,
 		.p_replen	= SM_monres_sz,
 		.p_statidx	= NSMPROC_MON,
@@ -323,8 +349,8 @@ static struct rpc_procinfo	nsm_procedures[] = {
 	},
 [NSMPROC_UNMON] = {
 		.p_proc		= NSMPROC_UNMON,
-		.p_encode	= (kxdrproc_t) xdr_encode_unmon,
-		.p_decode	= (kxdrproc_t) xdr_decode_stat,
+		.p_encode	= (kxdrproc_t)xdr_enc_unmon,
+		.p_decode	= (kxdrproc_t)xdr_dec_stat,
 		.p_arglen	= SM_mon_id_sz,
 		.p_replen	= SM_unmonres_sz,
 		.p_statidx	= NSMPROC_UNMON,