Commit 82efcab3 authored Mar 11, 2019 by Bart Van Assche Committed by Thomas Gleixner Mar 21, 2019

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: 009bb421 ("workqueue, lockdep: Fix an alloc_workqueue() error path")
Reported-by:  <syzbot+be0c198232f86389c3dd@syzkaller.appspotmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Qian Cai <cai@lca.pw>
Link: https://lkml.kernel.org/r/20190311230255.176081-1-bvanassche@acm.org

parent 9e98c678

kernel/workqueue.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -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;

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