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Subject: Re: [PATCH v2 4/7] NFSD: Use xdr_inline_decode() to decode NFSv3
 symlinks
From:   Jeff Layton <jlayton@kernel.org>
To:     Chuck Lever <chuck.lever@oracle.com>, linux-nfs@vger.kernel.org
Date:   Mon, 29 Aug 2022 09:48:28 -0400
In-Reply-To: <166171264105.21449.17586756015319208200.stgit@manet.1015granger.net>
References: <166171174172.21449.5036120183381273656.stgit@manet.1015granger.net>
         <166171264105.21449.17586756015319208200.stgit@manet.1015granger.net>
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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.
>=20
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  fs/nfsd/nfs3xdr.c |   14 +++-----------
>  1 file changed, 3 insertions(+), 11 deletions(-)
>=20
> 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, st=
ruct xdr_stream *xdr)
>  {
>  	struct nfsd3_symlinkargs *args =3D rqstp->rq_argp;
>  	struct kvec *head =3D rqstp->rq_arg.head;
> -	struct kvec *tail =3D rqstp->rq_arg.tail;
> -	size_t remaining;
> =20
>  	if (!svcxdr_decode_diropargs3(xdr, &args->ffh, &args->fname, &args->fle=
n))
>  		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;
> =20
> -	/* request sanity */
> -	remaining =3D head->iov_len + rqstp->rq_arg.page_len + tail->iov_len;
> -	remaining -=3D xdr_stream_pos(xdr);
> -	if (remaining < xdr_align_size(args->tlen))
> -		return false;
> -
> -	args->first.iov_base =3D xdr->p;
> +	/* symlink_data */
>  	args->first.iov_len =3D head->iov_len - xdr_stream_pos(xdr);
> -
> -	return true;
> +	args->first.iov_base =3D xdr_inline_decode(xdr, args->tlen);
> +	return args->first.iov_base !=3D NULL;
>  }
> =20
>  bool
>=20
>=20

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