stm32: Potential NULL pointer dereference in dcmi_irq_thread()

[Dmitriy Ulitin]

At the moment of enabling irq handling:

1922 ret = devm_request_threaded_irq(&pdev->dev, irq, dcmi_irq_callback,
1923			dcmi_irq_thread, IRQF_ONESHOT,
1924			dev_name(&pdev->dev), dcmi);

there is still uninitialized field sd_format of struct stm32_dcmi *dcmi.
If an interrupt occurs in the interval between the installation of the
interrupt handler and the initialization of this field, NULL pointer
dereference happens.

This field is dereferenced in the handler function without any check:

457 if (dcmi->sd_format->fourcc == V4L2_PIX_FMT_JPEG &&
458	    dcmi->misr & IT_FRAME) {

The patch moves interrupt handler installation
after initialization of the sd_format field that happens in
dcmi_graph_notify_complete() via dcmi_set_default_fmt().

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

Signed-off-by: Dmitriy Ulitin <ulitin@xxxxxxxxx>
Signed-off-by: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
---
 drivers/media/platform/stm32/stm32-dcmi.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/media/platform/stm32/stm32-dcmi.c b/drivers/media/platform/stm32/stm32-dcmi.c
index d9b4ad0abf0c..ada0c01dc1b1 100644
--- a/drivers/media/platform/stm32/stm32-dcmi.c
+++ b/drivers/media/platform/stm32/stm32-dcmi.c
@@ -128,6 +128,7 @@ struct stm32_dcmi {
 	int				sequence;
 	struct list_head		buffers;
 	struct dcmi_buf			*active;
+	int			irq;
 
 	struct v4l2_device		v4l2_dev;
 	struct video_device		*vdev;
@@ -1752,6 +1753,14 @@ static int dcmi_graph_notify_complete(struct v4l2_async_notifier *notifier)
 		return ret;
 	}
 
+	ret = devm_request_threaded_irq(dcmi->dev, dcmi->irq, dcmi_irq_callback,
+					dcmi_irq_thread, IRQF_ONESHOT,
+					dev_name(dcmi->dev), dcmi);
+	if (ret) {
+		dev_err(dcmi->dev, "Unable to request irq %d\n", dcmi->irq);
+		return ret;
+	}
+
 	return 0;
 }
 
@@ -1906,6 +1915,8 @@ static int dcmi_probe(struct platform_device *pdev)
 	irq = platform_get_irq(pdev, 0);
 	if (irq <= 0)
 		return irq ? irq : -ENXIO;
+
+	dcmi->irq = irq;
 
 	dcmi->res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!dcmi->res) {
@@ -1919,14 +1930,6 @@ static int dcmi_probe(struct platform_device *pdev)
 		return PTR_ERR(dcmi->regs);
 	}
 
-	ret = devm_request_threaded_irq(&pdev->dev, irq, dcmi_irq_callback,
-					dcmi_irq_thread, IRQF_ONESHOT,
-					dev_name(&pdev->dev), dcmi);
-	if (ret) {
-		dev_err(&pdev->dev, "Unable to request irq %d\n", irq);
-		return ret;
-	}
-
 	mclk = devm_clk_get(&pdev->dev, "mclk");
 	if (IS_ERR(mclk)) {
 		if (PTR_ERR(mclk) != -EPROBE_DEFER)
-- 
2.25.1