From: Benny Halevy Subject: Re: [PATCH version2] nfsd41: Fix a crash when a callback is retried Date: Thu, 01 Jul 2010 21:28:59 +0300 Message-ID: <4C2CDE6B.2050702@panasas.com> References: <4C28DCE0.7050201@panasas.com> <4C29DA23.90200@panasas.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: "J. Bruce Fields" , "Labiaga, Ricardo" , NFS list To: Boaz Harrosh Return-path: Received: from daytona.panasas.com ([67.152.220.89]:60284 "EHLO daytona.int.panasas.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758157Ab0GAS3B (ORCPT ); Thu, 1 Jul 2010 14:29:01 -0400 In-Reply-To: <4C29DA23.90200@panasas.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Jun. 29, 2010, 14:33 +0300, Boaz Harrosh wrote: > > If a callback is retried at nfsd4_cb_recall_done() do to > some error. The returned rpc reply would then crash here: > > @@ -514,6 +514,7 @@ decode_cb_sequence(struct xdr_stream *xdr, struct nfsd4_cb_sequence *res, > u32 dummy; > __be32 *p; > > + BUG_ON(!res); > if (res->cbs_minorversion == 0) > return 0; > > [BUG_ON added for demonstration] > > This is because the nfsd4_cb_done_sequence() has NULLed out > the task->tk_msg.rpc_resp pointer. > > Also eventually the rpc would use the new slot without making > sure it is free by calling nfsd41_cb_setup_sequence(). > > This problem was introduced by a 4.1 protocol addition patch: > [0421b5c5] nfsd41: Backchannel: Implement cb_recall over NFSv4.1 > > Which was overlooking the possibility of an RPC callback retries. > For not-4.1 case redoing the _prepare is harmless. > > Signed-off-by: Boaz Harrosh Merged at pnfs-all-2.6.35-rc3-2010-07-01 Thanks! Benny > --- > fs/nfsd/nfs4callback.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c > index f3b5015..3bbeae8 100644 > --- a/fs/nfsd/nfs4callback.c > +++ b/fs/nfsd/nfs4callback.c > @@ -913,7 +913,7 @@ static void nfsd4_cb_recall_done(struct rpc_task *task, void *calldata) > if (dp->dl_retries--) { > rpc_delay(task, 2*HZ); > task->tk_status = 0; > - rpc_restart_call(task); > + rpc_restart_call_prepare(task); > return; > } else { > atomic_set(&clp->cl_cb_set, 0);