dmaengine Archive on lore.kernel.org
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From: Logan Gunthorpe <logang@deltatee.com>
To: linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
	Vinod Koul <vkoul@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>,
	Logan Gunthorpe <logang@deltatee.com>
Subject: [PATCH 2/5] dmaengine: Call module_put() after device_free_chan_resources()
Date: Tue, 22 Oct 2019 15:46:13 -0600
Message-ID: <20191022214616.7943-3-logang@deltatee.com> (raw)
In-Reply-To: <20191022214616.7943-1-logang@deltatee.com>

The module reference is taken to ensure the callbacks still exist
when they are called. If the channel holds the last reference to the
module, the module can disappear before device_free_chan_resources() is
called and would cause a call into free'd memory.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 drivers/dma/dmaengine.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 4b604086b1b3..776fdf535a3a 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -250,7 +250,6 @@ static void dma_chan_put(struct dma_chan *chan)
 		return;
 
 	chan->client_count--;
-	module_put(dma_chan_to_owner(chan));
 
 	/* This channel is not in use anymore, free it */
 	if (!chan->client_count && chan->device->device_free_chan_resources) {
@@ -259,6 +258,8 @@ static void dma_chan_put(struct dma_chan *chan)
 		chan->device->device_free_chan_resources(chan);
 	}
 
+	module_put(dma_chan_to_owner(chan));
+
 	/* If the channel is used via a DMA request router, free the mapping */
 	if (chan->router && chan->router->route_free) {
 		chan->router->route_free(chan->router->dev, chan->route_data);
-- 
2.20.1


  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-22 21:46 [PATCH 0/5] PLX Switch DMA Engine Driver Logan Gunthorpe
2019-10-22 21:46 ` [PATCH 1/5] dmaengine: Store module owner in dma_device struct Logan Gunthorpe
2019-11-09 17:18   ` Vinod Koul
2019-11-11 16:50     ` Logan Gunthorpe
2019-11-12  5:56       ` Vinod Koul
2019-11-12 16:45         ` Logan Gunthorpe
2019-11-14  4:55           ` Vinod Koul
2019-11-14 17:03             ` Logan Gunthorpe
2019-11-22  5:20               ` Vinod Koul
2019-11-22 16:53                 ` Dave Jiang
2019-11-22 20:50                   ` Dan Williams
2019-11-22 20:56                     ` Logan Gunthorpe
2019-11-22 21:01                       ` Dan Williams
2019-11-22 21:42                         ` Dave Jiang
2019-12-10  9:53                           ` Vinod Koul
2019-12-10 17:39                             ` Logan Gunthorpe
2019-10-22 21:46 ` Logan Gunthorpe [this message]
2019-10-22 21:46 ` [PATCH 3/5] dmaengine: plx-dma: Introduce PLX DMA engine PCI driver skeleton Logan Gunthorpe
2019-11-09 17:35   ` Vinod Koul
2019-11-11 17:50     ` Logan Gunthorpe
2019-11-12  6:09       ` Vinod Koul
2019-11-12 17:22         ` Logan Gunthorpe
2019-10-22 21:46 ` [PATCH 4/5] dmaengine: plx-dma: Implement hardware initialization and cleanup Logan Gunthorpe
2019-10-22 21:46 ` [PATCH 5/5] dmaengine: plx-dma: Implement descriptor submission Logan Gunthorpe
2019-11-09 17:40   ` Vinod Koul
2019-11-11 18:11     ` Logan Gunthorpe

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