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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 554C5C4360C for ; Sun, 29 Sep 2019 13:57:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C505218AC for ; Sun, 29 Sep 2019 13:57:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569765421; bh=zBIgDdIM5oBN2pRQk15Qm3YAgRhv9IwZ7wotxvqQnIQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=oEBaie6aVBAyxw7f4QDDszLWAiTMP6j4J6QYwboSfBplaF1bl8Q01q5WOj7K+UDua 625ZyPzID+99TXKlEcABJloZV8YS0i4gW+pNhwczbQLQqWGCnnMMH5u+jwJhv3MBH0 l/GX/V+iTtwTlredI4CvOwWJSLZIRnMLv6nAfAFU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729088AbfI2N47 (ORCPT ); Sun, 29 Sep 2019 09:56:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:37082 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725974AbfI2N46 (ORCPT ); Sun, 29 Sep 2019 09:56:58 -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 0843421882; Sun, 29 Sep 2019 13:56:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569765417; bh=zBIgDdIM5oBN2pRQk15Qm3YAgRhv9IwZ7wotxvqQnIQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=meayJ8swhzsvhIh9tnQbkRZ46EKwS3obVC5rrDw3WrZem/jnqycBkuE5IS5lGYDnO +ka0ffWoAOvsco/PitndfrQz7z2w1AtRidtWn4zecsBUvg5LUBPOu4XFb+/XHE324+ +nx76KH6MR4N/DabTcuqx8gUMQOzdw2SSyPBVcs4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Aurelien Aptel , Pavel Shilovsky , Steve French Subject: [PATCH 4.19 14/63] CIFS: fix deadlock in cached root handling Date: Sun, 29 Sep 2019 15:53:47 +0200 Message-Id: <20190929135033.649952261@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190929135031.382429403@linuxfoundation.org> References: <20190929135031.382429403@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Aurelien Aptel commit 7e5a70ad88b1e6f6d9b934b2efb41afff496820f upstream. Prevent deadlock between open_shroot() and cifs_mark_open_files_invalid() by releasing the lock before entering SMB2_open, taking it again after and checking if we still need to use the result. Link: https://lore.kernel.org/linux-cifs/684ed01c-cbca-2716-bc28-b0a59a0f8521@prodrive-technologies.com/T/#u Fixes: 3d4ef9a15343 ("smb3: fix redundant opens on root") Signed-off-by: Aurelien Aptel Reviewed-by: Pavel Shilovsky Signed-off-by: Steve French CC: Stable Signed-off-by: Greg Kroah-Hartman --- fs/cifs/smb2ops.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -553,7 +553,50 @@ int open_shroot(unsigned int xid, struct oparams.fid = pfid; oparams.reconnect = false; + /* + * We do not hold the lock for the open because in case + * SMB2_open needs to reconnect, it will end up calling + * cifs_mark_open_files_invalid() which takes the lock again + * thus causing a deadlock + */ + mutex_unlock(&tcon->crfid.fid_mutex); rc = SMB2_open(xid, &oparams, &srch_path, &oplock, NULL, NULL, NULL); + mutex_lock(&tcon->crfid.fid_mutex); + + /* + * Now we need to check again as the cached root might have + * been successfully re-opened from a concurrent process + */ + + if (tcon->crfid.is_valid) { + /* work was already done */ + + /* stash fids for close() later */ + struct cifs_fid fid = { + .persistent_fid = pfid->persistent_fid, + .volatile_fid = pfid->volatile_fid, + }; + + /* + * Caller expects this func to set pfid to a valid + * cached root, so we copy the existing one and get a + * reference + */ + memcpy(pfid, tcon->crfid.fid, sizeof(*pfid)); + kref_get(&tcon->crfid.refcount); + + mutex_unlock(&tcon->crfid.fid_mutex); + + if (rc == 0) { + /* close extra handle outside of critical section */ + SMB2_close(xid, tcon, fid.persistent_fid, + fid.volatile_fid); + } + return 0; + } + + /* Cached root is still invalid, continue normaly */ + if (rc == 0) { memcpy(tcon->crfid.fid, pfid, sizeof(struct cifs_fid)); tcon->crfid.tcon = tcon; @@ -561,6 +604,7 @@ int open_shroot(unsigned int xid, struct kref_init(&tcon->crfid.refcount); kref_get(&tcon->crfid.refcount); } + mutex_unlock(&tcon->crfid.fid_mutex); return rc; }