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>

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 3f959c6..f9c052d 100644 (file)
--- 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)