linux-kernel - [PATCH 2/2] media: ti: j721e-csi2rx: Fix races while restarting DMA

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Date: Fri, 23 Feb 2024 13:53:02 +0530
From: Jai Luthra <j-luthra@...com>
To: Maxime Ripard <mripard@...nel.org>,
        Mauro Carvalho Chehab
	<mchehab@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Jack Zhu
	<jack.zhu@...rfivetech.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Vaishnav Achath <vaishnav.a@...com>,
        Tomi Valkeinen
	<tomi.valkeinen@...asonboard.com>
CC: <linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Julien
 Massot <julien.massot@...labora.com>,
        Changhuang Liang
	<Changhuang.liang@...rfivetech.com>,
        Jai Luthra <j-luthra@...com>
Subject: [PATCH 2/2] media: ti: j721e-csi2rx: Fix races while restarting
 DMA

After the frame is submitted to DMA, it may happen that the submitted
list is not updated soon enough, and the DMA callback is triggered
before that.

This can lead to kernel crashes, so move everything in a single
lock/unlock section to prevent such races.

Fixes: b4a3d877dc92 ("media: ti: Add CSI2RX support for J721E")
Signed-off-by: Jai Luthra <j-luthra@...com>
---
 drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
index 54aba055c96b..d47570f5d35a 100644
--- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
+++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
@@ -786,15 +786,14 @@ static void ti_csi2rx_buffer_queue(struct vb2_buffer *vb)
 			dev_warn(csi->dev,
 				 "Failed to drain DMA. Next frame might be bogus\n");
 
+		spin_lock_irqsave(&dma->lock, flags);
 		ret = ti_csi2rx_start_dma(csi, buf);
 		if (ret) {
-			dev_err(csi->dev, "Failed to start DMA: %d\n", ret);
-			spin_lock_irqsave(&dma->lock, flags);
 			vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
 			dma->state = TI_CSI2RX_DMA_IDLE;
 			spin_unlock_irqrestore(&dma->lock, flags);
+			dev_err(csi->dev, "Failed to start DMA: %d\n", ret);
 		} else {
-			spin_lock_irqsave(&dma->lock, flags);
 			list_add_tail(&buf->list, &dma->submitted);
 			spin_unlock_irqrestore(&dma->lock, flags);
 		}

-- 
2.43.0