SUNRPC: Fix locking around callback channel reply receive

Both xprt_lookup_rqst() and xprt_complete_rqst() require that you
take the transport lock in order to avoid races with xprt_transmit().

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: stable@vger.kernel.org
Reviewed-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 16 insertions, 11 deletions

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 3f959c681885..f9c052d508f0 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1019,17 +1019,12 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
         xid = *p++;
         calldir = *p;
 
-        if (bc_xprt)
-                req = xprt_lookup_rqst(bc_xprt, xid);
-
-        if (!req) {
-                printk(KERN_NOTICE
-                        "%s: Got unrecognized reply: "
-                        "calldir 0x%x xpt_bc_xprt %p xid %08x\n",
-                        __func__, ntohl(calldir),
-                        bc_xprt, ntohl(xid));
+        if (!bc_xprt)
                 return -EAGAIN;
-        }
+        spin_lock_bh(&bc_xprt->transport_lock);
+        req = xprt_lookup_rqst(bc_xprt, xid);
+        if (!req)
+                goto unlock_notfound;
 
         memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
         /*
@@ -1040,11 +1035,21 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
         dst = &req->rq_private_buf.head[0];
         src = &rqstp->rq_arg.head[0];
         if (dst->iov_len < src->iov_len)
-                return -EAGAIN; /* whatever; just giving up. */
+                goto unlock_eagain; /* whatever; just giving up. */
         memcpy(dst->iov_base, src->iov_base, src->iov_len);
         xprt_complete_rqst(req->rq_task, rqstp->rq_arg.len);
         rqstp->rq_arg.len = 0;
+        spin_unlock_bh(&bc_xprt->transport_lock);
         return 0;
+unlock_notfound:
+        printk(KERN_NOTICE
+                "%s: Got unrecognized reply: "
+                "calldir 0x%x xpt_bc_xprt %p xid %08x\n",
+                __func__, ntohl(calldir),
+                bc_xprt, ntohl(xid));
+unlock_eagain:
+        spin_unlock_bh(&bc_xprt->transport_lock);
+        return -EAGAIN;
 }
 
 static int copy_pages_to_kvecs(struct kvec *vec, struct page **pages, int len)