From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-1431546-1518324299-2-2466415216288647618 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1518324298; b=dYyhBlyeNrRFxsBOMJM2L1M0W2D63UBKjrS3NIgNSB4uECx mEUEHXUCQSbiMNqupU5PMssPJ0cPX/hdlLALNLHz4mSXckf6Ia9pV95OzH9ceWsA 4cHW9ES+0hYzONHE1rx+aHrKRxtF7TFkjRREtepWCOXJRFWZJkiLv96O1LGqTp8a o2BhySM5QWN4U53bisapOCCymnvzrU9oqjhJHNrPeKjMvJJHmT6wSPm1HoHPdwfL vF3LEDkuElYUvyMOIYTqpVwlSfKN/KvF5i4x4fpV5PELxJBTszvYM2F+etnghhwn vvaxZS/WoW0n60lLINsu59SVoeEbi0/8EGxZMew== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=content-type:content-transfer-encoding :mime-version:from:to:cc:date:message-id:subject:in-reply-to :sender:list-id; s=arctest; t=1518324298; bh=JRG144OaGBn2ysYfTZg DLWGaq+3J4bsbD6k49QUWJRQ=; b=B9/kzCEXtYfipLMqArdBibv4S+FnnmNY7Mi MSGWyit6lmVUfu7I8+OxjbhvpHYbGPItf8knpqyW8fJ0xMkrsnmsDl35xCAgvL6J QXcePAqrOgaZn3T6XU849cgeq343hivWFjWoUVwhtwAPNZRz0wmRXWS9Ee4Gk7Mu eN9JysrjbInfcvNRLPCvIIBv3n2i7IXc/W9poj3azLJCog9H82lYAsxw+8d+8YMQ 91djpz1BpoUc9r4XAO1iLPs1zb66tsQB4DmdQZ2WWHdfoWGljbYCjTuwYvZmFmka H1wWqqSMSlnJ1Tgxp6gOn6C5zpe7pA9csNxYQvgUU/0oIdv+EPw== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=decadent.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=decadent.org.uk header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753327AbeBKEnE (ORCPT ); Sat, 10 Feb 2018 23:43:04 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41895 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752874AbeBKEd7 (ORCPT ); Sat, 10 Feb 2018 23:33:59 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Hou Tao" , "Mike Snitzer" Date: Sun, 11 Feb 2018 04:31:11 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 074/136] dm: fix race between dm_get_from_kobject() and __dm_destroy() In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 3.16.54-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Hou Tao commit b9a41d21dceadf8104812626ef85dc56ee8a60ed upstream. The following BUG_ON was hit when testing repeat creation and removal of DM devices: kernel BUG at drivers/md/dm.c:2919! CPU: 7 PID: 750 Comm: systemd-udevd Not tainted 4.1.44 Call Trace: [] dm_get_from_kobject+0x34/0x3a [] dm_attr_show+0x2b/0x5e [] ? mutex_lock+0x26/0x44 [] sysfs_kf_seq_show+0x83/0xcf [] kernfs_seq_show+0x23/0x25 [] seq_read+0x16f/0x325 [] kernfs_fop_read+0x3a/0x13f [] __vfs_read+0x26/0x9d [] ? security_file_permission+0x3c/0x44 [] ? rw_verify_area+0x83/0xd9 [] vfs_read+0x8f/0xcf [] ? __fdget_pos+0x12/0x41 [] SyS_read+0x4b/0x76 [] system_call_fastpath+0x12/0x71 The bug can be easily triggered, if an extra delay (e.g. 10ms) is added between the test of DMF_FREEING & DMF_DELETING and dm_get() in dm_get_from_kobject(). To fix it, we need to ensure the test of DMF_FREEING & DMF_DELETING and dm_get() are done in an atomic way, so _minor_lock is used. The other callers of dm_get() have also been checked to be OK: some callers invoke dm_get() under _minor_lock, some callers invoke it under _hash_lock, and dm_start_request() invoke it after increasing md->open_count. Signed-off-by: Hou Tao Signed-off-by: Mike Snitzer Signed-off-by: Ben Hutchings --- drivers/md/dm.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -2912,11 +2912,15 @@ struct mapped_device *dm_get_from_kobjec md = container_of(kobj, struct mapped_device, kobj_holder.kobj); - if (test_bit(DMF_FREEING, &md->flags) || - dm_deleting_md(md)) - return NULL; - + spin_lock(&_minor_lock); + if (test_bit(DMF_FREEING, &md->flags) || dm_deleting_md(md)) { + md = NULL; + goto out; + } dm_get(md); +out: + spin_unlock(&_minor_lock); + return md; }