linux-kernel - [tip:locking/urgent] workqueue: Only unregister a registered lockdep key

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Date:   Thu, 21 Mar 2019 04:04:05 -0700
From:   tip-bot for Bart Van Assche <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, tglx@...utronix.de, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, peterz@...radead.org,
        mingo@...nel.org, cai@....pw, bvanassche@....org, tj@...nel.org
Subject: [tip:locking/urgent] workqueue: Only unregister a registered
 lockdep key

Commit-ID:  82efcab3b9f3ef59e9713237c6e3c05c3a95c1ae
Gitweb:     https://git.kernel.org/tip/82efcab3b9f3ef59e9713237c6e3c05c3a95c1ae
Author:     Bart Van Assche <bvanassche@....org>
AuthorDate: Mon, 11 Mar 2019 16:02:55 -0700
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 21 Mar 2019 12:00:18 +0100

workqueue: Only unregister a registered lockdep key

The recent change to prevent use after free and a memory leak introduced an
unconditional call to wq_unregister_lockdep() in the error handling
path. If the lockdep key had not been registered yet, then the lockdep core
emits a warning.

Only call wq_unregister_lockdep() if wq_register_lockdep() has been
called first.

Fixes: 009bb421b6ce ("workqueue, lockdep: Fix an alloc_workqueue() error path")
Reported-by: syzbot+be0c198232f86389c3dd@...kaller.appspotmail.com
Signed-off-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Tejun Heo <tj@...nel.org>
Cc: Qian Cai <cai@....pw>
Link: https://lkml.kernel.org/r/20190311230255.176081-1-bvanassche@acm.org

---
 kernel/workqueue.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 4026d1871407..ddee541ea97a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4266,7 +4266,7 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
 	INIT_LIST_HEAD(&wq->list);
 
 	if (alloc_and_link_pwqs(wq) < 0)
-		goto err_free_wq;
+		goto err_unreg_lockdep;
 
 	if (wq_online && init_rescuer(wq) < 0)
 		goto err_destroy;
@@ -4292,9 +4292,10 @@ struct workqueue_struct *alloc_workqueue(const char *fmt,
 
 	return wq;
 
-err_free_wq:
+err_unreg_lockdep:
 	wq_unregister_lockdep(wq);
 	wq_free_lockdep(wq);
+err_free_wq:
 	free_workqueue_attrs(wq->unbound_attrs);
 	kfree(wq);
 	return NULL;