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* [PATCH AUTOSEL 4.14 01/30] netfilter: nfnetlink: avoid deadlock due to synchronous request_module
@ 2019-08-02 13:23 Sasha Levin
  2019-08-02 13:23 ` [PATCH AUTOSEL 4.14 02/30] vfio-ccw: Set pa_nr to 0 if memory allocation fails for pa_iova_pfn Sasha Levin
                   ` (14 more replies)
  0 siblings, 15 replies; 20+ messages in thread
From: Sasha Levin @ 2019-08-02 13:23 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: Florian Westphal, Thomas Jarosch, Juliana Rodrigueiro,
	Pablo Neira Ayuso, Sasha Levin, netfilter-devel, coreteam, netdev

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 733d3e4a30d85..2cee032af46d2 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -530,7 +530,7 @@ 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


^ permalink raw reply related	[flat|nested] 20+ messages in thread

end of thread, other threads:[~2019-08-05  9:55 UTC | newest]

Thread overview: 20+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2019-08-02 13:23 [PATCH AUTOSEL 4.14 01/30] netfilter: nfnetlink: avoid deadlock due to synchronous request_module Sasha Levin
2019-08-02 13:23 ` [PATCH AUTOSEL 4.14 02/30] vfio-ccw: Set pa_nr to 0 if memory allocation fails for pa_iova_pfn Sasha Levin
2019-08-02 13:23 ` [PATCH AUTOSEL 4.14 03/30] netfilter: Fix rpfilter dropping vrf packets by mistake Sasha Levin
2019-08-02 13:23 ` [PATCH AUTOSEL 4.14 04/30] netfilter: nft_hash: fix symhash with modulus one Sasha Levin
2019-08-02 13:23 ` [PATCH AUTOSEL 4.14 07/30] mac80211: don't warn about CW params when not using them Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 08/30] hwmon: (nct6775) Fix register address and added missed tolerance for nct6106 Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 11/30] drm/msm: stop abusing dma_map/unmap for cache Sasha Levin
2019-08-02 18:06   ` [Freedreno] " Sean Paul
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 12/30] drm: silence variable 'conn' set but not used Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 13/30] cpufreq/pasemi: fix use-after-free in pas_cpufreq_cpu_init() Sasha Levin
2019-08-02 13:24   ` Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 14/30] s390/qdio: add sanity checks to the fast-requeue path Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 21/30] drbd: dynamically allocate shash descriptor Sasha Levin
2019-08-02 13:24   ` [Drbd-dev] " Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 22/30] ACPI/IORT: Fix off-by-one check in iort_dev_find_its_id() Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 24/30] scsi: megaraid_sas: fix panic on loading firmware crashdump Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 25/30] scsi: ibmvfc: fix WARN_ON during event pool release Sasha Levin
2019-08-02 13:24   ` Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 26/30] scsi: scsi_dh_alua: always use a 2 second delay before retrying RTPG Sasha Levin
2019-08-02 13:24 ` [PATCH AUTOSEL 4.14 28/30] sched/fair: Don't free p->numa_faults with concurrent readers Sasha Levin

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