From: "J. Bruce Fields" Subject: Re: [PATCH] NLM: hold BKL when clearing global lockd task and serv vars Date: Mon, 7 Apr 2008 13:56:15 -0400 Message-ID: <20080407175615.GD3305@fieldses.org> References: <1207575514-6703-1-git-send-email-jlayton@redhat.com> <1207575514-6703-2-git-send-email-jlayton@redhat.com> <20080407164500.GA17728@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jeff Layton , trond.myklebust@fys.uio.no, nfsv4@linux-nfs.org, linux-nfs@vger.kernel.org To: Christoph Hellwig Return-path: Received: from mail.fieldses.org ([66.93.2.214]:34085 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751719AbYDGR4b (ORCPT ); Mon, 7 Apr 2008 13:56:31 -0400 In-Reply-To: <20080407164500.GA17728@infradead.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Mon, Apr 07, 2008 at 12:45:01PM -0400, Christoph Hellwig wrote: > On Mon, Apr 07, 2008 at 09:38:34AM -0400, Jeff Layton wrote: > > The global task and serv pointers for lockd are normally protected by > > the nlmsvc_mutex. The exception is when the lockd exits abnormally. When > > this occurs, these variables are cleared without any locking. > > Shouldn't we get rid of the case where it exits abnormally instead? I tried to figure out when this could actually occur (when can svc_recv() return an error other than -EINTR or -EAGAIN?), and got lost in sock_recvmsg(): - svc_recv() itself returns only -EAGAIN or the return from ->xpo_recvfrom(). - the only xpo_recvfrom() that's interesting is svc_tcp_recvfrom(), which can return the error it gets from svc_recvfrom(), which can return the error from kernel_recvmsg(), which gets its return from sock_recvmsg(). Since __sock_recvmsg() has a security hook, it looks like we can end up with an -EACCES from selinux? So one case would be selinux deciding we weren't allowed to receive packets from this socket. Huh. --b.