From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Florian Westphal <fw@strlen.de>,
Thomas Jarosch <thomas.jarosch@intra2net.com>,
Juliana Rodrigueiro <juliana.rodrigueiro@intra2net.com>,
Pablo Neira Ayuso <pablo@netfilter.org>,
Sasha Levin <sashal@kernel.org>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
netdev@vger.kernel.org
Subject: [PATCH AUTOSEL 5.2 02/76] netfilter: nfnetlink: avoid deadlock due to synchronous request_module
Date: Fri, 2 Aug 2019 09:18:36 -0400 [thread overview]
Message-ID: <20190802131951.11600-2-sashal@kernel.org> (raw)
In-Reply-To: <20190802131951.11600-1-sashal@kernel.org>
From: Florian Westphal <fw@strlen.de>
[ Upstream commit 1b0890cd60829bd51455dc5ad689ed58c4408227 ]
Thomas and Juliana report a deadlock when running:
(rmmod nf_conntrack_netlink/xfrm_user)
conntrack -e NEW -E &
modprobe -v xfrm_user
They provided following analysis:
conntrack -e NEW -E
netlink_bind()
netlink_lock_table() -> increases "nl_table_users"
nfnetlink_bind()
# does not unlock the table as it's locked by netlink_bind()
__request_module()
call_usermodehelper_exec()
This triggers "modprobe nf_conntrack_netlink" from kernel, netlink_bind()
won't return until modprobe process is done.
"modprobe xfrm_user":
xfrm_user_init()
register_pernet_subsys()
-> grab pernet_ops_rwsem
..
netlink_table_grab()
calls schedule() as "nl_table_users" is non-zero
so modprobe is blocked because netlink_bind() increased
nl_table_users while also holding pernet_ops_rwsem.
"modprobe nf_conntrack_netlink" runs and inits nf_conntrack_netlink:
ctnetlink_init()
register_pernet_subsys()
-> blocks on "pernet_ops_rwsem" thanks to xfrm_user module
both modprobe processes wait on one another -- neither can make
progress.
Switch netlink_bind() to "nowait" modprobe -- this releases the netlink
table lock, which then allows both modprobe instances to complete.
Reported-by: Thomas Jarosch <thomas.jarosch@intra2net.com>
Reported-by: Juliana Rodrigueiro <juliana.rodrigueiro@intra2net.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nfnetlink.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 92077d4591090..4abbb452cf6c6 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -578,7 +578,7 @@ static int nfnetlink_bind(struct net *net, int group)
ss = nfnetlink_get_subsys(type << 8);
rcu_read_unlock();
if (!ss)
- request_module("nfnetlink-subsys-%d", type);
+ request_module_nowait("nfnetlink-subsys-%d", type);
return 0;
}
#endif
--
2.20.1
next parent reply other threads:[~2019-08-02 13:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190802131951.11600-1-sashal@kernel.org>
2019-08-02 13:18 ` Sasha Levin [this message]
2019-08-02 13:18 ` [PATCH AUTOSEL 5.2 05/76] netfilter: Fix rpfilter dropping vrf packets by mistake Sasha Levin
2019-08-02 13:18 ` [PATCH AUTOSEL 5.2 06/76] netfilter: nf_tables: fix module autoload for redir Sasha Levin
2019-08-02 13:18 ` [PATCH AUTOSEL 5.2 07/76] netfilter: conntrack: always store window size un-scaled Sasha Levin
2019-08-02 13:18 ` [PATCH AUTOSEL 5.2 08/76] netfilter: nft_hash: fix symhash with modulus one Sasha Levin
2019-08-02 13:18 ` [PATCH AUTOSEL 5.2 15/76] netfilter: nf_tables: Support auto-loading for inet nat Sasha Levin
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