linux-kernel - [PATCH 3/5] dma: dmatest: fix potential sign bug

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Date:	Sat, 17 Jul 2010 19:19:48 +0400
From:	Kulikov Vasiliy <segooon@...il.com>
To:	kernel-janitors@...r.kernel.org
Cc:	Dan Williams <dan.j.williams@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Maciej Sosnowski <maciej.sosnowski@...el.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Anatolij Gustschin <agust@...x.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/5] dma: dmatest: fix potential sign bug

'cnt' is unsigned, so this code may become wrong in future as
dmatest_add_threads() can return error code:

	cnt = dmatest_add_threads(dtc, DMA_MEMCPY);
	thread_count += cnt > 0 ? cnt : 0;
		        ^^^^^^^

Now it can return only -EINVAL if and only if second argument of
dmatest_add_threads() is not one of DMA_MEMCPY, DMA_XOR, DMA_PQ.
So, now it is not wrong but may become wrong in future.


The semantic patch that finds this problem (many false-positive results):
(http://coccinelle.lip6.fr/)

// <smpl>
@ r1 @
identifier f;
@@
int f(...) { ... }

@@
identifier r1.f;
type T;
unsigned T x;
@@

*x = f(...)
 ...
*x > 0

Signed-off-by: Kulikov Vasiliy <segooon@...il.com>
---
 drivers/dma/dmatest.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index 68d58c4..5589358 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -540,7 +540,7 @@ static int dmatest_add_channel(struct dma_chan *chan)
 	struct dmatest_chan	*dtc;
 	struct dma_device	*dma_dev = chan->device;
 	unsigned int		thread_count = 0;
-	unsigned int		cnt;
+	int cnt;
 
 	dtc = kmalloc(sizeof(struct dmatest_chan), GFP_KERNEL);
 	if (!dtc) {
-- 
1.7.0.4

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