Re: [PATCH v1 07/42] NFSD: Update WRITE3arg decoder to use struct xdr_stream

[bfields@fieldses.org (J. Bruce Fields)]

On Tue, Jan 05, 2021 at 10:30:18AM -0500, Chuck Lever wrote:
> As part of the update, open code that sanity-checks the size of the
> data payload against the length of the RPC Call message has to be
> re-implemented to use xdr_stream infrastructure.

I'm having a little trouble parsing that.  Did you mean "write code"?

--b.

> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  fs/nfsd/nfs3xdr.c |   51 ++++++++++++++++++++-------------------------------
>  1 file changed, 20 insertions(+), 31 deletions(-)
> 
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index ff98eae5db81..0aafb096de91 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -405,52 +405,41 @@ nfs3svc_decode_readargs(struct svc_rqst *rqstp, __be32 *p)
>  int
>  nfs3svc_decode_writeargs(struct svc_rqst *rqstp, __be32 *p)
>  {
> +	struct xdr_stream *xdr = &rqstp->rq_arg_stream;
>  	struct nfsd3_writeargs *args = rqstp->rq_argp;
> -	unsigned int len, hdr, dlen;
>  	u32 max_blocksize = svc_max_payload(rqstp);
>  	struct kvec *head = rqstp->rq_arg.head;
>  	struct kvec *tail = rqstp->rq_arg.tail;
> +	size_t remaining;
>  
> -	p = decode_fh(p, &args->fh);
> -	if (!p)
> +	if (!svcxdr_decode_nfs_fh3(xdr, &args->fh))
>  		return 0;
> -	p = xdr_decode_hyper(p, &args->offset);
> -
> -	args->count = ntohl(*p++);
> -	args->stable = ntohl(*p++);
> -	len = args->len = ntohl(*p++);
> -	if ((void *)p > head->iov_base + head->iov_len)
> +	if (xdr_stream_decode_u64(xdr, &args->offset) < 0)
>  		return 0;
> -	/*
> -	 * The count must equal the amount of data passed.
> -	 */
> -	if (args->count != args->len)
> +	if (xdr_stream_decode_u32(xdr, &args->count) < 0)
> +		return 0;
> +	if (xdr_stream_decode_u32(xdr, &args->stable) < 0)
>  		return 0;
>  
> -	/*
> -	 * Check to make sure that we got the right number of
> -	 * bytes.
> -	 */
> -	hdr = (void*)p - head->iov_base;
> -	dlen = head->iov_len + rqstp->rq_arg.page_len + tail->iov_len - hdr;
> -	/*
> -	 * Round the length of the data which was specified up to
> -	 * the next multiple of XDR units and then compare that
> -	 * against the length which was actually received.
> -	 * Note that when RPCSEC/GSS (for example) is used, the
> -	 * data buffer can be padded so dlen might be larger
> -	 * than required.  It must never be smaller.
> -	 */
> -	if (dlen < XDR_QUADLEN(len)*4)
> +	/* opaque data */
> +	if (xdr_stream_decode_u32(xdr, &args->len) < 0)
>  		return 0;
>  
> +	/* request sanity */
> +	if (args->count != args->len)
> +		return 0;
> +	remaining = head->iov_len + rqstp->rq_arg.page_len + tail->iov_len;
> +	remaining -= xdr_stream_pos(xdr);
> +	if (remaining < xdr_align_size(args->len))
> +		return 0;
>  	if (args->count > max_blocksize) {
>  		args->count = max_blocksize;
> -		len = args->len = max_blocksize;
> +		args->len = max_blocksize;
>  	}
>  
> -	args->first.iov_base = (void *)p;
> -	args->first.iov_len = head->iov_len - hdr;
> +	args->first.iov_base = xdr->p;
> +	args->first.iov_len = head->iov_len - xdr_stream_pos(xdr);
> +
>  	return 1;
>  }
>  
>