Commit efbdc769 authored Mar 21, 2020 by Logan Gunthorpe Committed by Peter Zijlstra Mar 21, 2020

PCI/switchtec: Fix init_completion race condition with poll_wait()



The call to init_completion() in mrpc_queue_cmd() can theoretically
race with the call to poll_wait() in switchtec_dev_poll().

  poll()			write()
    switchtec_dev_poll()   	  switchtec_dev_write()
      poll_wait(&s->comp.wait);      mrpc_queue_cmd()
			               init_completion(&s->comp)
				         init_waitqueue_head(&s->comp.wait)

To my knowledge, no one has hit this bug.

Fix this by using reinit_completion() instead of init_completion() in
mrpc_queue_cmd().

Fixes: 080b47de ("MicroSemi Switchtec management interface driver")

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lkml.kernel.org/r/20200313183608.2646-1-logang@deltatee.com

parent f6f48e18

drivers/pci/switch/switchtec.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -175,7 +175,7 @@ static int mrpc_queue_cmd(struct switchtec_user *stuser)
		kref_get(&stuser->kref);
		stuser->read_len = sizeof(stuser->data);
		stuser_set_state(stuser, MRPC_QUEUED);
		init_completion(&stuser->comp);
		reinit_completion(&stuser->comp);
		list_add_tail(&stuser->list, &stdev->mrpc_queue);

		mrpc_cmd_submit(stdev);

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