From: Boaz Harrosh Subject: [PATCH version2] nfsd41: Fix a crash when a callback is retried Date: Tue, 29 Jun 2010 14:33:55 +0300 Message-ID: <4C29DA23.90200@panasas.com> References: <4C28DCE0.7050201@panasas.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: "J. Bruce Fields" , Benny Halevy , "Labiaga, Ricardo" , NFS list Return-path: Received: from daytona.panasas.com ([67.152.220.89]:54248 "EHLO daytona.int.panasas.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751761Ab0F2Ld6 (ORCPT ); Tue, 29 Jun 2010 07:33:58 -0400 In-Reply-To: <4C28DCE0.7050201@panasas.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: 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 --- 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); -- 1.6.6.1