From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754018AbbGWQ7X (ORCPT ); Thu, 23 Jul 2015 12:59:23 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:41509 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753223AbbGWQ7U (ORCPT ); Thu, 23 Jul 2015 12:59:20 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Linus Torvalds Cc: Linux Containers , , , Andy Lutomirski , "Serge E. Hallyn" Date: Thu, 23 Jul 2015 11:52:48 -0500 Message-ID: <87r3nyak9r.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX18w6m4VpW8984eT3bYNquDbJIVRYn486wI= X-SA-Exim-Connect-IP: 67.3.205.90 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 TVD_RCVD_IP Message was received from an IP address * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject * 1.2 XMSubMetaSxObfu_03 Obfuscated Sexy Noun-People * 1.0 XMSubMetaSx_00 1+ Sexy Words X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: **;Linus Torvalds X-Spam-Relay-Country: X-Spam-Timing: total 574 ms - load_scoreonly_sql: 0.05 (0.0%), signal_user_changed: 5 (0.9%), b_tie_ro: 3.4 (0.6%), parse: 1.57 (0.3%), extract_message_metadata: 8 (1.4%), get_uri_detail_list: 3.2 (0.6%), tests_pri_-1000: 4.9 (0.9%), tests_pri_-950: 1.49 (0.3%), tests_pri_-900: 1.27 (0.2%), tests_pri_-400: 35 (6.1%), check_bayes: 34 (5.9%), b_tokenize: 8 (1.4%), b_tok_get_all: 11 (1.9%), b_comp_prob: 2.6 (0.5%), b_tok_touch_all: 8 (1.3%), b_finish: 2.4 (0.4%), tests_pri_0: 497 (86.6%), tests_pri_500: 4.3 (0.7%), rewrite_mail: 0.00 (0.0%) Subject: [GIT PULL] namespace: Infinite loop bugfixes for 4.2-rc4 X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 24 Sep 2014 11:00:52 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, Please pull the for-linus branch from the git tree: git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git for-linus HEAD: fe78fcc85a2046c51f1535710996860557eeec20 mnt: In detach_mounts detach the appropriate unmounted mount While reading through the code of detach_mounts I realized the code was a slightly off. Testing it revealed two buggy corner cases that can send the code of detach_mounts into an infinite loop. Fixing the code to do the right thing removes the possibility of these user triggered infinite loops in the code. Eric W. Biederman (2): mnt: Clarify and correct the disconnect logic in umount_tree mnt: In detach_mounts detach the appropriate unmounted mount fs/namespace.c | 42 +++++++++++++++++++++++++++++++++--------- fs/pnode.h | 2 -- 2 files changed, 33 insertions(+), 11 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index c7cb8a526c05..2b8aa15fd6df 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1361,6 +1361,36 @@ enum umount_tree_flags { UMOUNT_PROPAGATE = 2, UMOUNT_CONNECTED = 4, }; + +static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) +{ + /* Leaving mounts connected is only valid for lazy umounts */ + if (how & UMOUNT_SYNC) + return true; + + /* A mount without a parent has nothing to be connected to */ + if (!mnt_has_parent(mnt)) + return true; + + /* Because the reference counting rules change when mounts are + * unmounted and connected, umounted mounts may not be + * connected to mounted mounts. + */ + if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) + return true; + + /* Has it been requested that the mount remain connected? */ + if (how & UMOUNT_CONNECTED) + return false; + + /* Is the mount locked such that it needs to remain connected? */ + if (IS_MNT_LOCKED(mnt)) + return false; + + /* By default disconnect the mount */ + return true; +} + /* * mount_lock must be held * namespace_sem must be held for write @@ -1398,10 +1428,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how) if (how & UMOUNT_SYNC) p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; - disconnect = !(((how & UMOUNT_CONNECTED) && - mnt_has_parent(p) && - (p->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) || - IS_MNT_LOCKED_AND_LAZY(p)); + disconnect = disconnect_mount(p, how); pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, disconnect ? &unmounted : NULL); @@ -1538,11 +1565,8 @@ void __detach_mounts(struct dentry *dentry) while (!hlist_empty(&mp->m_list)) { mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); if (mnt->mnt.mnt_flags & MNT_UMOUNT) { - struct mount *p, *tmp; - list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { - hlist_add_head(&p->mnt_umount.s_list, &unmounted); - umount_mnt(p); - } + hlist_add_head(&mnt->mnt_umount.s_list, &unmounted); + umount_mnt(mnt); } else umount_tree(mnt, UMOUNT_CONNECTED); } diff --git a/fs/pnode.h b/fs/pnode.h index 7114ce6e6b9e..0fcdbe7ca648 100644 --- a/fs/pnode.h +++ b/fs/pnode.h @@ -20,8 +20,6 @@ #define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED) #define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED) #define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED) -#define IS_MNT_LOCKED_AND_LAZY(m) \ - (((m)->mnt.mnt_flags & (MNT_LOCKED|MNT_SYNC_UMOUNT)) == MNT_LOCKED) #define CL_EXPIRE 0x01 #define CL_SLAVE 0x02