Hi Ben,
I've hit a few problems with this patch after it went upstream.
On Fri, Nov 20, 2015 at 6:55 AM, Benjamin Coddington
<bcodding@xxxxxxxxxx> wrote:
> A truncated cb_compound request will cause the client to decode null or
> data from a previous callback for nfs4.1 backchannel case, or uninitialized
> data for the nfs4.0 case. This is because the path through
> svc_process_common() advances the request's iov_base and decrements iov_len
> without adjusting the overall xdr_buf's len field. That causes
> xdr_init_decode() to set up the xdr_stream with an incorrect length in
> nfs4_callback_compound().
>
> Fixing this for the nfs4.1 backchannel case first requires setting the
> correct iov_len and page_len based on the length of received data in the
> same manner as the nfs4.0 case.
>
> Then the request's xdr_buf length can be adjusted for both cases based upon
> the remaining iov_len and page_len.
>
> Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
> ---
> fs/nfs/callback_xdr.c | 7 +++++--
> net/sunrpc/backchannel_rqst.c | 8 ++++++++
> net/sunrpc/svc.c | 1 +
> 3 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
> index 6b1697a..1c8213e 100644
> --- a/fs/nfs/callback_xdr.c
> +++ b/fs/nfs/callback_xdr.c
> @@ -76,7 +76,8 @@ static __be32 *read_buf(struct xdr_stream *xdr, int nbytes)
>
> p = xdr_inline_decode(xdr, nbytes);
> if (unlikely(p == NULL))
> - printk(KERN_WARNING "NFS: NFSv4 callback reply buffer overflowed!\n");
> + printk(KERN_WARNING "NFS: NFSv4 callback reply buffer overflowed "
> + "or truncated request.\n");
> return p;
> }
>
> @@ -892,6 +893,7 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r
> struct cb_compound_hdr_arg hdr_arg = { 0 };
> struct cb_compound_hdr_res hdr_res = { NULL };
> struct xdr_stream xdr_in, xdr_out;
> + struct xdr_buf *rq_arg = &rqstp->rq_arg;
> __be32 *p, status;
> struct cb_process_state cps = {
> .drc_status = 0,
> @@ -903,7 +905,8 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r
>
> dprintk("%s: start\n", __func__);
>
> - xdr_init_decode(&xdr_in, &rqstp->rq_arg, rqstp->rq_arg.head[0].iov_base);
> + rq_arg->len = rq_arg->head[0].iov_len + rq_arg->page_len;
This is redundant.
> + xdr_init_decode(&xdr_in, rq_arg, rq_arg->head[0].iov_base);
>
> p = (__be32*)((char *)rqstp->rq_res.head[0].iov_base + rqstp->rq_res.head[0].iov_len);
> xdr_init_encode(&xdr_out, &rqstp->rq_res, p);
> diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
> index 6255d14..d92cee1 100644
> --- a/net/sunrpc/backchannel_rqst.c
> +++ b/net/sunrpc/backchannel_rqst.c
> @@ -333,12 +333,20 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
> {
> struct rpc_xprt *xprt = req->rq_xprt;
> struct svc_serv *bc_serv = xprt->bc_serv;
> + struct xdr_buf *rq_rcv_buf = &req->rq_rcv_buf;
>
> spin_lock(&xprt->bc_pa_lock);
> list_del(&req->rq_bc_pa_list);
> xprt_dec_alloc_count(xprt, 1);
> spin_unlock(&xprt->bc_pa_lock);
>
> + if (copied <= rq_rcv_buf->head[0].iov_len) {
> + rq_rcv_buf->head[0].iov_len = copied;
> + rq_rcv_buf->page_len = 0;
> + } else {
> + rq_rcv_buf->page_len = copied - rq_rcv_buf->head[0].iov_len;
> + }
> +
There is a problem with this approach: req->rq_rcv_buf is never reset,
and so NFSv4 callbacks are now broken.
The correct fix for this issue is to do the above adjustment in
bc_svc_process(), so that it only applies to the resulting
rqstp->rq_arg.
> req->rq_private_buf.len = copied;
> set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
>
> diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> index a8f579d..af9f987 100644
> --- a/net/sunrpc/svc.c
> +++ b/net/sunrpc/svc.c
> @@ -1363,6 +1363,7 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req,
> memcpy(&rqstp->rq_addr, &req->rq_xprt->addr, rqstp->rq_addrlen);
> memcpy(&rqstp->rq_arg, &req->rq_rcv_buf, sizeof(rqstp->rq_arg));
> memcpy(&rqstp->rq_res, &req->rq_snd_buf, sizeof(rqstp->rq_res));
> + rqstp->rq_arg.len = req->rq_private_buf.len;
Cheers
Trond
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