Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   madhuparnabhowmik10@gmail.com
To:     paul@crapouillou.net, Zubair.Kakakhel@imgtec.com,
        dan.j.williams@intel.com, vkoul@kernel.org
Cc:     dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
        andrianov@ispras.ru, ldv-project@linuxtesting.org,
        Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Subject: [PATCH] drivers/dma/dma-jz4780: Fix race condition between probe and irq handler
Date:   Sun, 16 Aug 2020 12:52:53 +0530
Message-Id: <20200816072253.13817-1-madhuparnabhowmik10@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>

In probe IRQ is requested before zchan->id is initialized which can be
read in the irq handler. Hence, shift request irq and enable clock after
other initializations complete. Here, enable clock part is not part of
the race, it is just shifted down after request_irq to keep the error
path same as before.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
---
 drivers/dma/dma-jz4780.c | 44 ++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index 448f663da89c..5cbc8c3bd6c7 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/drivers/dma/dma-jz4780.c
@@ -879,28 +879,6 @@ static int jz4780_dma_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	ret = platform_get_irq(pdev, 0);
-	if (ret < 0)
-		return ret;
-
-	jzdma->irq = ret;
-
-	ret = request_irq(jzdma->irq, jz4780_dma_irq_handler, 0, dev_name(dev),
-			  jzdma);
-	if (ret) {
-		dev_err(dev, "failed to request IRQ %u!\n", jzdma->irq);
-		return ret;
-	}
-
-	jzdma->clk = devm_clk_get(dev, NULL);
-	if (IS_ERR(jzdma->clk)) {
-		dev_err(dev, "failed to get clock\n");
-		ret = PTR_ERR(jzdma->clk);
-		goto err_free_irq;
-	}
-
-	clk_prepare_enable(jzdma->clk);
-
 	/* Property is optional, if it doesn't exist the value will remain 0. */
 	of_property_read_u32_index(dev->of_node, "ingenic,reserved-channels",
 				   0, &jzdma->chan_reserved);
@@ -949,6 +927,28 @@ static int jz4780_dma_probe(struct platform_device *pdev)
 		jzchan->vchan.desc_free = jz4780_dma_desc_free;
 	}
 
+	ret = platform_get_irq(pdev, 0);
+	if (ret < 0)
+		return ret;
+
+	jzdma->irq = ret;
+
+	ret = request_irq(jzdma->irq, jz4780_dma_irq_handler, 0, dev_name(dev),
+			  jzdma);
+	if (ret) {
+		dev_err(dev, "failed to request IRQ %u!\n", jzdma->irq);
+		return ret;
+	}
+
+	jzdma->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(jzdma->clk)) {
+		dev_err(dev, "failed to get clock\n");
+		ret = PTR_ERR(jzdma->clk);
+		goto err_free_irq;
+	}
+
+	clk_prepare_enable(jzdma->clk);
+
 	ret = dmaenginem_async_device_register(dd);
 	if (ret) {
 		dev_err(dev, "failed to register device\n");
-- 
2.17.1