linux-kernel - [PATCH AUTOSEL 4.4 09/30] dmaengine: pl330: fix irq race with terminate

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Message-ID: <20180907003853.57942-9-alexander.levin@microsoft.com>
Date:   Fri, 7 Sep 2018 00:39:02 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     John Keeping <john@...anate.com>, Vinod Koul <vkoul@...nel.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.4 09/30] dmaengine: pl330: fix irq race with
 terminate_all

From: John Keeping <john@...anate.com>

[ Upstream commit e49756544a21f5625b379b3871d27d8500764670 ]

In pl330_update() when checking if a channel has been aborted, the
channel's lock is not taken, only the overall pl330_dmac lock.  But in
pl330_terminate_all() the aborted flag (req_running==-1) is set under
the channel lock and not the pl330_dmac lock.

With threaded interrupts, this leads to a potential race:

    pl330_terminate_all	        pl330_update
    -------------------         ------------
    lock channel
                                entry
    lock pl330
    _stop channel
    unlock pl330
                                lock pl330
                                check req_running != -1
    req_running = -1
                                _start channel

Signed-off-by: John Keeping <john@...anate.com>
Signed-off-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/dma/pl330.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 8db791ef2027..95619ee33112 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -2132,13 +2132,14 @@ static int pl330_terminate_all(struct dma_chan *chan)
 
 	pm_runtime_get_sync(pl330->ddma.dev);
 	spin_lock_irqsave(&pch->lock, flags);
+
 	spin_lock(&pl330->lock);
 	_stop(pch->thread);
-	spin_unlock(&pl330->lock);
-
 	pch->thread->req[0].desc = NULL;
 	pch->thread->req[1].desc = NULL;
 	pch->thread->req_running = -1;
+	spin_unlock(&pl330->lock);
+
 	power_down = pch->active;
 	pch->active = false;
 
-- 
2.17.1