[PATCH v3 03/15] media: microchip-isc: fix race condition on stream stop

[Balakrishnan Sambath <balakrishnan.s@microchip.com>]

Disable histogram and drain AWB work queue before releasing DMA
buffers to prevent use-after-free if histogram IRQ fires during
stream stop.

Fixes: 91b4e487b0c6 ("media: microchip: add ISC driver as Microchip ISC")
Cc: stable@vger.kernel.org
Signed-off-by: Balakrishnan Sambath <balakrishnan.s@microchip.com>
---
 .../platform/microchip/microchip-isc-base.c   | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/microchip/microchip-isc-base.c b/drivers/media/platform/microchip/microchip-isc-base.c
index 45b94f1e89d8..b19c5a63b4bd 100644
--- a/drivers/media/platform/microchip/microchip-isc-base.c
+++ b/drivers/media/platform/microchip/microchip-isc-base.c
@@ -427,6 +427,14 @@ static void isc_stop_streaming(struct vb2_queue *vq)
 
 	mutex_unlock(&isc->awb_mutex);
 
+	/*
+	 * Disable the histogram so the ISR stops firing HISREQ, then drain
+	 * any work that was already queued before returning.  This must happen
+	 * after releasing awb_mutex because isc_awb_work also takes it.
+	 */
+	isc_set_histogram(isc, false);
+	cancel_work_sync(&isc->awb_work);
+
 	/* Disable DMA interrupt */
 	regmap_write(isc->regmap, ISC_INTDIS, ISC_INT_DDONE);
 
@@ -1519,10 +1527,17 @@ static int isc_s_awb_ctrl(struct v4l2_ctrl *ctrl)
 		}
 		mutex_unlock(&isc->awb_mutex);
 
-		/* if we have autowhitebalance on, start histogram procedure */
+		/*
+		 * If AWB auto mode is requested and we are streaming RAW,
+		 * start the histogram procedure, but only if it is not
+		 * already running. Repeated enable requests would reset
+		 * hist_id, preventing the 4-channel Bayer cycle from
+		 * completing.
+		 */
 		if (ctrls->awb == ISC_WB_AUTO &&
 		    vb2_is_streaming(&isc->vb2_vidq) &&
-		    ISC_IS_FORMAT_RAW(isc->config.sd_format->mbus_code))
+		    ISC_IS_FORMAT_RAW(isc->config.sd_format->mbus_code) &&
+		    ctrls->hist_stat != HIST_ENABLED)
 			isc_set_histogram(isc, true);
 
 		/*
-- 
2.34.1