linux-kernel - [PATCH] dlm: free workqueues after the connections

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Date:   Sat,  8 Oct 2016 10:14:37 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Christine Caulfield <ccaulfie@...hat.com>,
        David Teigland <teigland@...hat.com>
Cc:     cluster-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH] dlm: free workqueues after the connections

After backporting commit ee44b4bc054a ("dlm: use sctp 1-to-1 API")
series to a kernel with an older workqueue which didn't use RCU yet, it
was noticed that we are freeing the workqueues in dlm_lowcomms_stop()
too early as free_conn() will try to access that memory for canceling
the queued works if any.

This issue was introduced by commit 0d737a8cfd83 as before it such
attempt to cancel the queued works wasn't performed, so the issue was
not present.

This patch fixes it by simply inverting the free order.

Cc: stable@...r.kernel.org
Fixes: 0d737a8cfd83 ("dlm: fix race while closing connections")
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
---
 fs/dlm/lowcomms.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 963016c8f3d12def89c9803eb9d124caa2385dc4..609998de533e894d9cb98f3ff7ef3e05b41d424a 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1656,16 +1656,12 @@ void dlm_lowcomms_stop(void)
 	mutex_lock(&connections_lock);
 	dlm_allow_conn = 0;
 	foreach_conn(stop_conn);
+	clean_writequeues();
+	foreach_conn(free_conn);
 	mutex_unlock(&connections_lock);

 	work_stop();

-	mutex_lock(&connections_lock);
-	clean_writequeues();
-
-	foreach_conn(free_conn);
-
-	mutex_unlock(&connections_lock);
 	kmem_cache_destroy(con_cache);
 }

-- 
2.7.4