Re: [PATCH] svcrpc: explicitly reject compounds that are not padded out to 4-byte multiple

From: "J. Bruce Fields" <bfields@fieldses.org>
To: Jeff Layton <jlayton@redhat.com>
Cc: linux-nfs@vger.kernel.org
Subject: Re: [PATCH] svcrpc: explicitly reject compounds that are not padded out to 4-byte multiple
Date: Mon, 10 Mar 2014 15:48:33 -0400	[thread overview]
Message-ID: <20140310194833.GG28006@fieldses.org> (raw)
In-Reply-To: <1394465695-727-1-git-send-email-jlayton@redhat.com>

On Mon, Mar 10, 2014 at 11:34:55AM -0400, Jeff Layton wrote:
> We have a WARN_ON in the nfsd4_decode_write() that tells us when the
> client has sent a request that is not padded out properly according to
> RFC4506. A WARN_ON really isn't appropriate in this case though since
> this indicates a client bug, not a server one.
> 
> Move this check out to the top-level compound decoder and have it just
> explicitly return an error. Also add a dprintk() that shows the client
> address and xid to help track down clients and frames that trigger it.

OK, thanks.--b.

> 
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
>  fs/nfsd/nfs4xdr.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 63f2395c57ed..3a491dade169 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -1222,7 +1222,6 @@ nfsd4_decode_write(struct nfsd4_compoundargs *argp, struct nfsd4_write *write)
>  	}
>  	write->wr_head.iov_base = p;
>  	write->wr_head.iov_len = avail;
> -	WARN_ON(avail != (XDR_QUADLEN(avail) << 2));
>  	write->wr_pagelist = argp->pagelist;
>  
>  	len = XDR_QUADLEN(write->wr_buflen) << 2;
> @@ -3691,6 +3690,12 @@ int nfsd4_release_compoundargs(void *rq, __be32 *p, void *resp)
>  int
>  nfs4svc_decode_compoundargs(struct svc_rqst *rqstp, __be32 *p, struct nfsd4_compoundargs *args)
>  {
> +	if (rqstp->rq_arg.head[0].iov_len % 4) {
> +		/* client is nuts */
> +		dprintk("%s: compound not properly padded! (peeraddr=%pISc xid=0x%x)",
> +			__func__, svc_addr(rqstp), be32_to_cpu(rqstp->rq_xid));
> +		return 0;
> +	}
>  	args->p = p;
>  	args->end = rqstp->rq_arg.head[0].iov_base + rqstp->rq_arg.head[0].iov_len;
>  	args->pagelist = rqstp->rq_arg.pages;
> -- 
> 1.8.5.3
> 