Re: [PATCH v2 4/7] NFSD: Use xdr_inline_decode() to decode NFSv3 symlinks

[Jeff Layton <jlayton@kernel.org>]

On Sun, 2022-08-28 at 14:50 -0400, Chuck Lever wrote:
> Replace the check for buffer over/underflow with a helper that is
> commonly used for this purpose. The helper also sets xdr->nwords
> correctly after successfully linearizing the symlink argument into
> the stream's scratch buffer.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  fs/nfsd/nfs3xdr.c |   14 +++-----------
>  1 file changed, 3 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
> index 0293b8d65f10..71e32cf28885 100644
> --- a/fs/nfsd/nfs3xdr.c
> +++ b/fs/nfsd/nfs3xdr.c
> @@ -616,8 +616,6 @@ nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
>  {
>  	struct nfsd3_symlinkargs *args = rqstp->rq_argp;
>  	struct kvec *head = rqstp->rq_arg.head;
> -	struct kvec *tail = rqstp->rq_arg.tail;
> -	size_t remaining;
>  
>  	if (!svcxdr_decode_diropargs3(xdr, &args->ffh, &args->fname, &args->flen))
>  		return false;
> @@ -626,16 +624,10 @@ nfs3svc_decode_symlinkargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
>  	if (xdr_stream_decode_u32(xdr, &args->tlen) < 0)
>  		return false;
>  
> -	/* 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 false;
> -
> -	args->first.iov_base = xdr->p;
> +	/* symlink_data */
>  	args->first.iov_len = head->iov_len - xdr_stream_pos(xdr);
> -
> -	return true;
> +	args->first.iov_base = xdr_inline_decode(xdr, args->tlen);
> +	return args->first.iov_base != NULL;
>  }
>  
>  bool
> 
> 

Reviewed-by: Jeff Layton <jlayton@kernel.org>