linux-kernel - [PATCH] dmaengine: fix regression introduced by d6103085dfd83c13db65c3bd7e182f021d77c541

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Message-ID: <Pine.LNX.4.64.0903311755540.4806@axis700.grange>
Date:	Tue, 31 Mar 2009 18:07:34 +0200 (CEST)
From:	Guennadi Liakhovetski <lg@...x.de>
To:	linux-kernel@...r.kernel.org
cc:	Atsushi Nemoto <anemo@....ocn.ne.jp>,
	Dan Williams <dan.j.williams@...el.com>,
	Maciej Sosnowski <maciej.sosnowski@...el.com>
Subject: [PATCH] dmaengine: fix regression introduced by
 d6103085dfd83c13db65c3bd7e182f021d77c541

chan is an index variable, used to loop over a list of channels, and here 
it is used _after_ the loop, in which case it doesn't point to a DMA 
channel struct anymore. Dereferencing it leads to a corruption of a random 
memory location, which in my case was a pointer inside a clock struct. Fix 
it by using a local variable pointing to the DMA device.

Signed-off-by: Guennadi Liakhovetski <lg@...x.de>
---

Guys, this was a _real_ bad joke, cost me almost a day, and that patch has 
been reviewed by two persons...

<rant>
So far 2.6.29(-next) has been very bad for me, regressions all over the 
place, lots of wasted time hunting them down:-(
</rant>

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 59e0fb2..92438e9 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -726,7 +726,7 @@ int dma_async_device_register(struct dma_device *device)
 		}
 	list_add_tail_rcu(&device->global_node, &dma_device_list);
 	if (dma_has_cap(DMA_PRIVATE, device->cap_mask))
-		chan->device->privatecnt++;	/* Always private */
+		device->privatecnt++;	/* Always private */
 	dma_channel_rebalance();
 	mutex_unlock(&dma_list_mutex);
 
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