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

J. Bruce Fields
2021-01-22T19:40:01Z

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;
> }
>
>