From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760150Ab3LFX1F (ORCPT ); Fri, 6 Dec 2013 18:27:05 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:48996 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162436Ab3LFXUo (ORCPT ); Fri, 6 Dec 2013 18:20:44 -0500 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Trond Myklebust , Kamal Mostafa Subject: [PATCH 3.8 099/152] SUNRPC: Avoid deep recursion in rpc_release_client Date: Fri, 6 Dec 2013 15:10:23 -0800 Message-Id: <1386371476-2477-100-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1386371476-2477-1-git-send-email-kamal@canonical.com> References: <1386371476-2477-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8.13.14 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Trond Myklebust commit d07ba8422f1e58be94cc98a1f475946dc1b89f1b upstream. In cases where an rpc client has a parent hierarchy, then rpc_free_client may end up calling rpc_release_client() on the parent, thus recursing back into rpc_free_client. If the hierarchy is deep enough, then we can get into situations where the stack simply overflows. The fix is to have rpc_release_client() loop so that it can take care of the parent rpc client hierarchy without needing to recurse. Reported-by: Jeff Layton Reported-by: Weston Andros Adamson Reported-by: Bruce Fields Link: http://lkml.kernel.org/r/2C73011F-0939-434C-9E4D-13A1EB1403D7@netapp.com Signed-off-by: Trond Myklebust Signed-off-by: Kamal Mostafa --- net/sunrpc/clnt.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index 1a3bd4d..d8b6ad9 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -624,14 +624,16 @@ EXPORT_SYMBOL_GPL(rpc_shutdown_client); /* * Free an RPC client */ -static void +static struct rpc_clnt * rpc_free_client(struct rpc_clnt *clnt) { + struct rpc_clnt *parent = NULL; + dprintk_rcu("RPC: destroying %s client for %s\n", clnt->cl_protname, rcu_dereference(clnt->cl_xprt)->servername); if (clnt->cl_parent != clnt) - rpc_release_client(clnt->cl_parent); + parent = clnt->cl_parent; rpc_clnt_remove_pipedir(clnt); rpc_unregister_client(clnt); rpc_free_iostats(clnt->cl_metrics); @@ -640,18 +642,17 @@ rpc_free_client(struct rpc_clnt *clnt) xprt_put(rcu_dereference_raw(clnt->cl_xprt)); rpciod_down(); kfree(clnt); + return parent; } /* * Free an RPC client */ -static void +static struct rpc_clnt * rpc_free_auth(struct rpc_clnt *clnt) { - if (clnt->cl_auth == NULL) { - rpc_free_client(clnt); - return; - } + if (clnt->cl_auth == NULL) + return rpc_free_client(clnt); /* * Note: RPCSEC_GSS may need to send NULL RPC calls in order to @@ -662,7 +663,8 @@ rpc_free_auth(struct rpc_clnt *clnt) rpcauth_release(clnt->cl_auth); clnt->cl_auth = NULL; if (atomic_dec_and_test(&clnt->cl_count)) - rpc_free_client(clnt); + return rpc_free_client(clnt); + return NULL; } /* @@ -673,10 +675,13 @@ rpc_release_client(struct rpc_clnt *clnt) { dprintk("RPC: rpc_release_client(%p)\n", clnt); - if (list_empty(&clnt->cl_tasks)) - wake_up(&destroy_wait); - if (atomic_dec_and_test(&clnt->cl_count)) - rpc_free_auth(clnt); + do { + if (list_empty(&clnt->cl_tasks)) + wake_up(&destroy_wait); + if (!atomic_dec_and_test(&clnt->cl_count)) + break; + clnt = rpc_free_auth(clnt); + } while (clnt != NULL); } /** -- 1.8.3.2