[PATCH v2 095/118] NFSD: Update the SYMLINK3args decoder to use struct xdr_stream

[Chuck Lever <chuck.lever@oracle.com>]

Similar to the WRITE decoder, code that checks the sanity of the
payload size is re-wired to work with xdr_stream infrastructure.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs3xdr.c |   33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index ec4778f01472..6dfab4bd6c2c 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -623,26 +623,29 @@ nfs3svc_decode_mkdirargs(struct svc_rqst *rqstp, __be32 *p)
 int
 nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, __be32 *p)
 {
+	struct xdr_stream *xdr = &rqstp->rq_xdr_stream;
 	struct nfsd3_symlinkargs *args = rqstp->rq_argp;
-	char *base = (char *)p;
-	size_t dlen;
+	struct kvec *head = rqstp->rq_arg.head;
+	struct kvec *tail = rqstp->rq_arg.tail;
+	size_t remaining;
 
-	if (!(p = decode_fh(p, &args->ffh)) ||
-	    !(p = decode_filename(p, &args->fname, &args->flen)))
-		return 0;
-	p = decode_sattr3(p, &args->attrs, nfsd_user_namespace(rqstp));
+	if (!svcxdr_decode_diropargs3(xdr, &args->ffh, &args->fname, &args->flen))
+		return XDR_DECODE_FAILED;
+	if (!svcxdr_decode_sattr3(rqstp, xdr, &args->attrs))
+		return XDR_DECODE_FAILED;
+	if (xdr_stream_decode_u32(xdr, &args->tlen) < 0)
+		return XDR_DECODE_FAILED;
 
-	args->tlen = ntohl(*p++);
+	/* request sanity */
+	remaining = head->iov_len + rqstp->rq_arg.page_len + tail->iov_len;
+	remaining -= xdr_stream_pos(xdr);
+	if (remaining < xdr_align_size(args->tlen))
+		return XDR_DECODE_FAILED;
 
-	args->first.iov_base = p;
-	args->first.iov_len = rqstp->rq_arg.head[0].iov_len;
-	args->first.iov_len -= (char *)p - base;
+	args->first.iov_base = xdr->p;
+	args->first.iov_len = head->iov_len - xdr_stream_pos(xdr);
 
-	dlen = args->first.iov_len + rqstp->rq_arg.page_len +
-	       rqstp->rq_arg.tail[0].iov_len;
-	if (dlen < XDR_QUADLEN(args->tlen) << 2)
-		return 0;
-	return 1;
+	return XDR_DECODE_DONE;
 }
 
 int