From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47242) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eMySX-0003bq-0U for qemu-devel@nongnu.org; Thu, 07 Dec 2017 10:51:37 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eMyST-0008B8-Ux for qemu-devel@nongnu.org; Thu, 07 Dec 2017 10:51:36 -0500 Received: from [195.214.232.25] (port=1321 helo=relay.sw.ru) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eMyST-00089L-KF for qemu-devel@nongnu.org; Thu, 07 Dec 2017 10:51:33 -0500 From: Vladimir Sementsov-Ogievskiy Date: Thu, 7 Dec 2017 18:50:57 +0300 Message-Id: <20171207155102.66622-2-vsementsov@virtuozzo.com> In-Reply-To: <20171207155102.66622-1-vsementsov@virtuozzo.com> References: <20171207155102.66622-1-vsementsov@virtuozzo.com> Subject: [Qemu-devel] [PATCH v2 1/6] nbd/server: add additional assert to nbd_export_put List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: armbru@redhat.com, dgilbert@redhat.com, pbonzini@redhat.com, eblake@redhat.com, mreitz@redhat.com, kwolf@redhat.com, vsementsov@virtuozzo.com, den@openvz.org This place is not obvious, nbd_export_close may theoretically reduce refcount to 0. It may happen if someone calls nbd_export_put on named export not through nbd_export_set_name when refcount is 1. Signed-off-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Eric Blake Reviewed-by: Max Reitz --- nbd/server.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/nbd/server.c b/nbd/server.c index 92c0fdd03b..e817c48087 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -1190,6 +1190,12 @@ void nbd_export_put(NBDExport *exp) nbd_export_close(exp); } + /* nbd_export_close() may theoretically reduce refcount to 0. It may happen + * if someone calls nbd_export_put() on named export not through + * nbd_export_set_name() when refcount is 1. So, let's assert that + * it is > 0. + */ + assert(exp->refcount > 0); if (--exp->refcount == 0) { assert(exp->name == NULL); assert(exp->description == NULL); -- 2.11.1