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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Logan Gunthorpe <logang@deltatee.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Sasha Levin <sashal@kernel.org>,
	linux-pci@vger.kernel.org
Subject: [PATCH AUTOSEL 5.4 21/46] PCI/switchtec: Fix init_completion race condition with poll_wait()
Date: Thu,  9 Apr 2020 23:48:44 -0400	[thread overview]
Message-ID: <20200410034909.8922-21-sashal@kernel.org> (raw)
In-Reply-To: <20200410034909.8922-1-sashal@kernel.org>

From: Logan Gunthorpe <logang@deltatee.com>

[ Upstream commit efbdc769601f4d50018bf7ca50fc9f7c67392ece ]

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: 080b47def5e5 ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/switch/switchtec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
index cc43c855452f7..2c9c3061894b2 100644
--- a/drivers/pci/switch/switchtec.c
+++ b/drivers/pci/switch/switchtec.c
@@ -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);
-- 
2.20.1


           reply	other threads:[~2020-04-10  3:56 UTC|newest]

Thread overview: expand[flat|nested]  mbox.gz  Atom feed
 [parent not found: <20200410034909.8922-1-sashal@kernel.org>]

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