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From: Lukas Wunner <>
To: Vinod Koul <>
Cc:,,, Mark Brown <>,
	Nathan Chancellor <>
Subject: [PATCH] dmaengine: Fix access to uninitialized dma_slave_caps
Date: Thu, 5 Dec 2019 12:54:49 +0100
Message-ID: <> (raw)
In-Reply-To: <>

dmaengine_desc_set_reuse() allocates a struct dma_slave_caps on the
stack, populates it using dma_get_slave_caps() and then accesses one
of its members.

However dma_get_slave_caps() may fail and this isn't accounted for,
leading to a legitimate warning of gcc-4.9 (but not newer versions):

   In file included from drivers/spi/spi-bcm2835.c:19:0:
   drivers/spi/spi-bcm2835.c: In function 'dmaengine_desc_set_reuse':
>> include/linux/dmaengine.h:1370:10: warning: 'caps.descriptor_reuse' is used uninitialized in this function [-Wuninitialized]
     if (caps.descriptor_reuse) {

Fix it, thereby also silencing the gcc-4.9 warning.

The issue has been present for 4 years but surfaces only now that
the first caller of dmaengine_desc_set_reuse() has been added in
spi-bcm2835.c. Another user of reusable DMA descriptors has existed
for a while in pxa_camera.c, but it sets the DMA_CTRL_REUSE flag
directly instead of calling dmaengine_desc_set_reuse(). Nevertheless,
tag this commit for stable in case there are out-of-tree users.

Fixes: 272420214d26 ("dmaengine: Add DMA_CTRL_REUSE")
Reported-by: kbuild test robot <>
Signed-off-by: Lukas Wunner <>
Cc: # v4.3+
 include/linux/dmaengine.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 8fcdee1c0cf9..dad4a68fa009 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -1364,8 +1364,11 @@ static inline int dma_get_slave_caps(struct dma_chan *chan,
 static inline int dmaengine_desc_set_reuse(struct dma_async_tx_descriptor *tx)
 	struct dma_slave_caps caps;
+	int ret;
-	dma_get_slave_caps(tx->chan, &caps);
+	ret = dma_get_slave_caps(tx->chan, &caps);
+	if (ret)
+		return ret;
 	if (caps.descriptor_reuse) {
 		tx->flags |= DMA_CTRL_REUSE;

       reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2019-12-05 11:54 ` Lukas Wunner [this message]
2019-12-11 10:33   ` Vinod Koul

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