From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54A7BC31E45 for ; Thu, 13 Jun 2019 16:12:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2A0A220665 for ; Thu, 13 Jun 2019 16:12:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560442370; bh=R+J2GFuWWAezQyQpmaUHq2znXbw+AdAzBsI4QI5nUWc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rMNMcFXird478XawDSFJDX8P2eeojb81gs+pLs5t5knCEGvcCbusVa953Yd5Z1WwE 8n6ucIEUT92jQy+ZAT7Ru2Y4y1tCNTrIO4aMOOqRwnziZ/gPIgSrDr4J7YUqfHSD+U uqy+0Xkf+KlsUBkwhvYHMhN/5bwsRYuT/P97t3xE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391672AbfFMQMn (ORCPT ); Thu, 13 Jun 2019 12:12:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:60242 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731220AbfFMInI (ORCPT ); Thu, 13 Jun 2019 04:43:08 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ACB4820851; Thu, 13 Jun 2019 08:43:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1560415387; bh=R+J2GFuWWAezQyQpmaUHq2znXbw+AdAzBsI4QI5nUWc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Gsxc4NkMoH5iSllwy4WkSOOKTmQCkur2mPeZ0Qlig9n2bjcSTD1gghSvk6XjNEyf6 VrkDo3OLdyjW8iNMeLiRjAvZE2WN6INskzszHjJPrvh8fTMEsxU7F5du6dZJkRBEER ZTY8mk/plD/5EsuNQCRdn9bcEF4L+3mOhgh1oVsE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "J. Bruce Fields" , Sasha Levin Subject: [PATCH 4.19 067/118] nfsd: allow fh_want_write to be called twice Date: Thu, 13 Jun 2019 10:33:25 +0200 Message-Id: <20190613075647.736790333@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190613075643.642092651@linuxfoundation.org> References: <20190613075643.642092651@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit 0b8f62625dc309651d0efcb6a6247c933acd8b45 ] A fuzzer recently triggered lockdep warnings about potential sb_writers deadlocks caused by fh_want_write(). Looks like we aren't careful to pair each fh_want_write() with an fh_drop_write(). It's not normally a problem since fh_put() will call fh_drop_write() for us. And was OK for NFSv3 where we'd do one operation that might call fh_want_write(), and then put the filehandle. But an NFSv4 protocol fuzzer can do weird things like call unlink twice in a compound, and then we get into trouble. I'm a little worried about this approach of just leaving everything to fh_put(). But I think there are probably a lot of fh_want_write()/fh_drop_write() imbalances so for now I think we need it to be more forgiving. Signed-off-by: J. Bruce Fields Signed-off-by: Sasha Levin --- fs/nfsd/vfs.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/nfsd/vfs.h b/fs/nfsd/vfs.h index a7e107309f76..db351247892d 100644 --- a/fs/nfsd/vfs.h +++ b/fs/nfsd/vfs.h @@ -120,8 +120,11 @@ void nfsd_put_raparams(struct file *file, struct raparms *ra); static inline int fh_want_write(struct svc_fh *fh) { - int ret = mnt_want_write(fh->fh_export->ex_path.mnt); + int ret; + if (fh->fh_want_write) + return 0; + ret = mnt_want_write(fh->fh_export->ex_path.mnt); if (!ret) fh->fh_want_write = true; return ret; -- 2.20.1