linux-kernel - [PATCH AUTOSEL for 4.9 30/55] lockd: fix "list_add double add" caused by legacy signal interface

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180124041521.32223-30-alexander.levin@microsoft.com>
Date:   Wed, 24 Jan 2018 04:15:44 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Vasily Averin <vvs@...tuozzo.com>,
        "J . Bruce Fields" <bfields@...hat.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.9 30/55] lockd: fix "list_add double add" caused
 by legacy signal interface

From: Vasily Averin <vvs@...tuozzo.com>

[ Upstream commit 81833de1a46edce9ca20cfe079872ac1c20ef359 ]

restart_grace() uses hardcoded init_net.
It can cause to "list_add double add" in following scenario:

1) nfsd and lockd was started in several net namespaces
2) nfsd in init_net was stopped (lockd was not stopped because
 it have users from another net namespaces)
3) lockd got signal, called restart_grace() -> set_grace_period()
 and enabled lock_manager in hardcoded init_net.
4) nfsd in init_net is started again,
 its lockd_up() calls set_grace_period() and tries to add
 lock_manager into init_net 2nd time.

Jeff Layton suggest:
"Make it safe to call locks_start_grace multiple times on the same
lock_manager. If it's already on the global grace_list, then don't try
to add it again.  (But we don't intentionally add twice, so for now we
WARN about that case.)

With this change, we also need to ensure that the nfsd4 lock manager
initializes the list before we call locks_start_grace. While we're at
it, move the rest of the nfsd_net initialization into
nfs4_state_create_net. I see no reason to have it spread over two
functions like it is today."

Suggested patch was updated to generate warning in described situation.

Suggested-by: Jeff Layton <jlayton@...hat.com>
Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 fs/nfs_common/grace.c | 6 +++++-
 fs/nfsd/nfs4state.c   | 7 ++++---
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c
index e280e9c9ebf3..77d136ac8909 100644
--- a/fs/nfs_common/grace.c
+++ b/fs/nfs_common/grace.c
@@ -30,7 +30,11 @@ locks_start_grace(struct net *net, struct lock_manager *lm)
 	struct list_head *grace_list = net_generic(net, grace_net_id);

 	spin_lock(&grace_lock);
-	list_add(&lm->list, grace_list);
+	if (list_empty(&lm->list))
+		list_add(&lm->list, grace_list);
+	else
+		WARN(1, "double list_add attempt detected in net %x %s\n",
+		     net->ns.inum, (net == &init_net) ? "(init_net)" : "");
 	spin_unlock(&grace_lock);
 }
 EXPORT_SYMBOL_GPL(locks_start_grace);
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 4df65926dae0..186550b35e1b 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -7009,6 +7009,10 @@ static int nfs4_state_create_net(struct net *net)
 		INIT_LIST_HEAD(&nn->sessionid_hashtbl[i]);
 	nn->conf_name_tree = RB_ROOT;
 	nn->unconf_name_tree = RB_ROOT;
+	nn->boot_time = get_seconds();
+	nn->grace_ended = false;
+	nn->nfsd4_manager.block_opens = true;
+	INIT_LIST_HEAD(&nn->nfsd4_manager.list);
 	INIT_LIST_HEAD(&nn->client_lru);
 	INIT_LIST_HEAD(&nn->close_lru);
 	INIT_LIST_HEAD(&nn->del_recall_lru);
@@ -7066,9 +7070,6 @@ nfs4_state_start_net(struct net *net)
 	ret = nfs4_state_create_net(net);
 	if (ret)
 		return ret;
-	nn->boot_time = get_seconds();
-	nn->grace_ended = false;
-	nn->nfsd4_manager.block_opens = true;
 	locks_start_grace(net, &nn->nfsd4_manager);
 	nfsd4_client_tracking_init(net);
 	printk(KERN_INFO "NFSD: starting %ld-second grace period (net %p)\n",
-- 
2.11.0