This is a latent bug. xdr_stream_pos works by subtracting
xdr_stream::nwords from xdr_buf::len. But xdr_stream::nwords is not
initialized by xdr_init_encode().
It works today only because all fields in rpcrdma_req::rl_stream
are initialized to zero by rpcrdma_req_create, making the
subtraction in xdr_stream_pos always a no-op.
I found this issue via code inspection. It was introduced by commit
39f4cd9e9982 ("xprtrdma: Harden chunk list encoding against send
buffer overflow"), but the code has changed enough since then that
this fix can't be automatically applied to stable.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
include/trace/events/rpcrdma.h | 9 +++++----
net/sunrpc/xprtrdma/rpc_rdma.c | 6 +++---
2 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/include/trace/events/rpcrdma.h b/include/trace/events/rpcrdma.h
index f0678e3..59492a93 100644
--- a/include/trace/events/rpcrdma.h
+++ b/include/trace/events/rpcrdma.h
@@ -470,13 +470,12 @@
TRACE_EVENT(xprtrdma_marshal,
TP_PROTO(
- const struct rpc_rqst *rqst,
- unsigned int hdrlen,
+ const struct rpcrdma_req *req,
unsigned int rtype,
unsigned int wtype
),
- TP_ARGS(rqst, hdrlen, rtype, wtype),
+ TP_ARGS(req, rtype, wtype),
TP_STRUCT__entry(
__field(unsigned int, task_id)
@@ -491,10 +490,12 @@
),
TP_fast_assign(
+ const struct rpc_rqst *rqst = &req->rl_slot;
+
__entry->task_id = rqst->rq_task->tk_pid;
__entry->client_id = rqst->rq_task->tk_client->cl_clid;
__entry->xid = be32_to_cpu(rqst->rq_xid);
- __entry->hdrlen = hdrlen;
+ __entry->hdrlen = req->rl_hdrbuf.len;
__entry->headlen = rqst->rq_snd_buf.head[0].iov_len;
__entry->pagelen = rqst->rq_snd_buf.page_len;
__entry->taillen = rqst->rq_snd_buf.tail[0].iov_len;
diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 85115a2..97bfb80 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -867,12 +867,12 @@ static bool rpcrdma_prepare_msg_sges(struct rpcrdma_xprt *r_xprt,
if (ret)
goto out_err;
- trace_xprtrdma_marshal(rqst, xdr_stream_pos(xdr), rtype, wtype);
-
- ret = rpcrdma_prepare_send_sges(r_xprt, req, xdr_stream_pos(xdr),
+ ret = rpcrdma_prepare_send_sges(r_xprt, req, req->rl_hdrbuf.len,
&rqst->rq_snd_buf, rtype);
if (ret)
goto out_err;
+
+ trace_xprtrdma_marshal(req, rtype, wtype);
return 0;
out_err:
