nbd: Fully initialize client in case of failed negotiation
If a non-NBD client connects to qemu-nbd, we would end up with
a SIGSEGV in nbd_client_put() because we were trying to
unregister the client's association to the export, even though
we skipped inserting the client into that list. Easy trigger
in two terminals:
$ qemu-nbd -p 30001 --format=raw file
$ nmap 127.0.0.1 -p 30001
nmap claims that it thinks it connected to a pago-services1
server (which probably means nmap could be updated to learn the
NBD protocol and give a more accurate diagnosis of the open
port - but that's not our problem), then terminates immediately,
so our call to nbd_negotiate() fails. The fix is to reorder
nbd_co_client_start() to ensure that all initialization occurs
before we ever try talking to a client in nbd_negotiate(), so
that the teardown sequence on negotiation failure doesn't fault
while dereferencing a half-initialized object.
While debugging this, I also noticed that nbd_update_server_watch()
called by nbd_client_closed() was still adding a channel to accept
the next client, even when the state was no longer RUNNING. That
is fixed by making nbd_can_accept() pay attention to the current
state.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1451614
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170527030421.28366-1-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/qemu-nbd.c b/qemu-nbd.c
index f60842f..651f85e 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -325,7 +325,7 @@
static int nbd_can_accept(void)
{
- return nb_fds < shared;
+ return state == RUNNING && nb_fds < shared;
}
static void nbd_export_closed(NBDExport *exp)
