From: Jeff Layton Subject: [PATCH 5/5] NLM: have nlm_shutdown_hosts kill off all NLM RPC tasks Date: Thu, 10 Jan 2008 13:01:36 -0500 Message-ID: <1199988096-19700-6-git-send-email-jlayton@redhat.com> References: <1199988096-19700-1-git-send-email-jlayton@redhat.com> <1199988096-19700-2-git-send-email-jlayton@redhat.com> <1199988096-19700-3-git-send-email-jlayton@redhat.com> <1199988096-19700-4-git-send-email-jlayton@redhat.com> <1199988096-19700-5-git-send-email-jlayton@redhat.com> Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org To: akpm@linux-foundation.org, neilb@suse.de Return-path: Received: from mx1.redhat.com ([66.187.233.31]:42079 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755491AbYAJSCV (ORCPT ); Thu, 10 Jan 2008 13:02:21 -0500 In-Reply-To: <1199988096-19700-5-git-send-email-jlayton@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: The main problem is this: When a lock that a client is blocking on comes free, lockd does this in nlmsvc_grant_blocked(): nlm_async_call(block->b_call, NLMPROC_GRANTED_MSG, &nlmsvc_grant_ops); the callback from this call is nlmsvc_grant_callback(). That function does this at the end to wake up lockd: svc_wake_up(block->b_daemon); However there is no guarantee that lockd will be up when this happens. If someone shuts down or restarts lockd before the async call completes, then the b_daemon pointer will point to freed memory and the kernel may oops. If we're shutting down all the nlm_hosts anyway, then it doesn't make sense to allow RPC calls to linger. Allowing them to do so can mean that the RPC calls can outlive the currently running lockd and can lead to the above use after free situation and possibly others. Signed-off-by: Jeff Layton --- fs/lockd/host.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/fs/lockd/host.c b/fs/lockd/host.c index 572601e..8771484 100644 --- a/fs/lockd/host.c +++ b/fs/lockd/host.c @@ -377,8 +377,10 @@ nlm_shutdown_hosts(void) /* First, make all hosts eligible for gc */ dprintk("lockd: nuking all hosts...\n"); for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) { - hlist_for_each_entry(host, pos, chain, h_hash) + hlist_for_each_entry(host, pos, chain, h_hash) { host->h_expires = jiffies - 1; + rpc_killall_tasks(host->h_rpcclnt); + } } /* Then, perform a garbage collection pass */ -- 1.5.3.7