From df8ad9f128c15aa0a0ebc7b24e9a22c9775b67af Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Fri, 26 May 2017 22:04:21 -0500 Subject: 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 Message-Id: <20170527030421.28366-1-eblake@redhat.com> Signed-off-by: Paolo Bonzini --- qemu-nbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'qemu-nbd.c') diff --git a/qemu-nbd.c b/qemu-nbd.c index f60842fd86..651f85ecc1 100644 --- a/qemu-nbd.c +++ b/qemu-nbd.c @@ -325,7 +325,7 @@ out: static int nbd_can_accept(void) { - return nb_fds < shared; + return state == RUNNING && nb_fds < shared; } static void nbd_export_closed(NBDExport *exp) -- cgit v1.2.3-55-g7522