From patchwork Tue Jun 28 18:07:10 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 12898644 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 09679CCA479 for ; Tue, 28 Jun 2022 18:07:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233960AbiF1SHR (ORCPT ); Tue, 28 Jun 2022 14:07:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233856AbiF1SHQ (ORCPT ); Tue, 28 Jun 2022 14:07:16 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 41D211EACC; Tue, 28 Jun 2022 11:07:15 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id A4FBACE21BF; Tue, 28 Jun 2022 18:07:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9D353C3411D; Tue, 28 Jun 2022 18:07:11 +0000 (UTC) Subject: [PATCH v2 13/31] NFSD: WARN when freeing an item still linked via nf_lru From: Chuck Lever To: linux-nfs@vger.kernel.org, netdev@vger.kernel.org Cc: david@fromorbit.com, jlayton@redhat.com, tgraf@suug.ch Date: Tue, 28 Jun 2022 14:07:10 -0400 Message-ID: <165643963066.84360.17047678502830993413.stgit@manet.1015granger.net> In-Reply-To: <165643915086.84360.2809940286726976517.stgit@manet.1015granger.net> References: <165643915086.84360.2809940286726976517.stgit@manet.1015granger.net> User-Agent: StGit/1.5.dev2+g9ce680a5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Add a guardrail to prevent freeing memory that is still on a list. This includes either a dispose list or the LRU list. This is the sign of a bug, but this class of bugs can be detected so that they don't endanger system stability, especially while debugging. Signed-off-by: Chuck Lever --- fs/nfsd/filecache.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 3055a04eeabe..8ade3699664c 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -220,6 +220,14 @@ nfsd_file_free(struct nfsd_file *nf) fput(nf->nf_file); flush = true; } + + /* + * If this item is still linked via nf_lru, that's a bug. + * WARN and leak it to preserve system stability. + */ + if (WARN_ON_ONCE(!list_empty(&nf->nf_lru))) + return flush; + call_rcu(&nf->nf_rcu, nfsd_file_slab_free); return flush; } @@ -349,7 +357,7 @@ nfsd_file_dispose_list(struct list_head *dispose) while(!list_empty(dispose)) { nf = list_first_entry(dispose, struct nfsd_file, nf_lru); - list_del(&nf->nf_lru); + list_del_init(&nf->nf_lru); nfsd_file_flush(nf); nfsd_file_put_noref(nf); } @@ -363,7 +371,7 @@ nfsd_file_dispose_list_sync(struct list_head *dispose) while(!list_empty(dispose)) { nf = list_first_entry(dispose, struct nfsd_file, nf_lru); - list_del(&nf->nf_lru); + list_del_init(&nf->nf_lru); nfsd_file_flush(nf); if (!refcount_dec_and_test(&nf->nf_ref)) continue;