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Date: Sun, 28 Jul 2019 18:32:24 +0000 From: Dexuan Cui <decui@...rosoft.com> To: Sunil Muthuswamy <sunilmut@...rosoft.com>, David Miller <davem@...emloft.net>, "netdev@...r.kernel.org" <netdev@...r.kernel.org> CC: KY Srinivasan <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, Stephen Hemminger <sthemmin@...rosoft.com>, "sashal@...nel.org" <sashal@...nel.org>, Michael Kelley <mikelley@...rosoft.com>, "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "olaf@...fle.de" <olaf@...fle.de>, "apw@...onical.com" <apw@...onical.com>, "jasowang@...hat.com" <jasowang@...hat.com>, vkuznets <vkuznets@...hat.com>, "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com> Subject: [PATCH net] hv_sock: Fix hang when a connection is closed hvs_do_close_lock_held() may decrease the reference count to 0 and free the sk struct completely, and then the following release_sock(sk) may hang. Fixes: a9eeb998c28d ("hv_sock: Add support for delayed close") Signed-off-by: Dexuan Cui <decui@...rosoft.com> Cc: stable@...r.kernel.org --- With the proper kernel debugging options enabled, first a warning can appear: kworker/1:0/4467 is freeing memory ..., with a lock still held there! stack backtrace: Workqueue: events vmbus_onmessage_work [hv_vmbus] Call Trace: dump_stack+0x67/0x90 debug_check_no_locks_freed.cold.52+0x78/0x7d slab_free_freelist_hook+0x85/0x140 kmem_cache_free+0xa5/0x380 __sk_destruct+0x150/0x260 hvs_close_connection+0x24/0x30 [hv_sock] vmbus_onmessage_work+0x1d/0x30 [hv_vmbus] process_one_work+0x241/0x600 worker_thread+0x3c/0x390 kthread+0x11b/0x140 ret_from_fork+0x24/0x30 and then the following release_sock(sk) can hang: watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [kworker/1:0:4467] ... irq event stamp: 62890 CPU: 1 PID: 4467 Comm: kworker/1:0 Tainted: G W 5.2.0+ #39 Workqueue: events vmbus_onmessage_work [hv_vmbus] RIP: 0010:queued_spin_lock_slowpath+0x2b/0x1e0 ... Call Trace: do_raw_spin_lock+0xab/0xb0 release_sock+0x19/0xb0 vmbus_onmessage_work+0x1d/0x30 [hv_vmbus] process_one_work+0x241/0x600 worker_thread+0x3c/0x390 kthread+0x11b/0x140 ret_from_fork+0x24/0x30 net/vmw_vsock/hyperv_transport.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c index f2084e3f7aa4..efbda8ef1eff 100644 --- a/net/vmw_vsock/hyperv_transport.c +++ b/net/vmw_vsock/hyperv_transport.c @@ -309,9 +309,16 @@ static void hvs_close_connection(struct vmbus_channel *chan) { struct sock *sk = get_per_channel_state(chan); + /* Grab an extra reference since hvs_do_close_lock_held() may decrease + * the reference count to 0 by calling sock_put(sk). + */ + sock_hold(sk); + lock_sock(sk); hvs_do_close_lock_held(vsock_sk(sk), true); release_sock(sk); + + sock_put(sk); } static void hvs_open_connection(struct vmbus_channel *chan) -- 2.19.1
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