linux-kernel - [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip

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Message-Id: <20220818203308.439043-4-nicolas.dufresne@collabora.com>
Date:   Thu, 18 Aug 2022 16:33:08 -0400
From:   Nicolas Dufresne <nicolas.dufresne@...labora.com>
To:     linux-media@...r.kernel.org, Maxime Ripard <mripard@...nel.org>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>
Cc:     kernel@...labora.com,
        Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        stable@...r.kernel.org,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()

From: Dmitry Osipenko <dmitry.osipenko@...labora.com>

The busy status bit may never de-assert if number of programmed skip
bits is incorrect, resulting in a kernel hang because the bit is polled
endlessly in the code. Fix it by adding timeout for the bit-polling.
This problem is reproducible by setting the data_bit_offset field of
the HEVC slice params to a wrong value by userspace.

Cc: stable@...r.kernel.org
Reported-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
---
 drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
index f703c585d91c5..f0bc118021b0a 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
@@ -227,6 +227,7 @@ static void cedrus_h265_pred_weight_write(struct cedrus_dev *dev,
 static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
 {
 	int count = 0;
+	u32 reg;
 
 	while (count < num) {
 		int tmp = min(num - count, 32);
@@ -234,8 +235,9 @@ static void cedrus_h265_skip_bits(struct cedrus_dev *dev, int num)
 		cedrus_write(dev, VE_DEC_H265_TRIGGER,
 			     VE_DEC_H265_TRIGGER_FLUSH_BITS |
 			     VE_DEC_H265_TRIGGER_TYPE_N_BITS(tmp));
-		while (cedrus_read(dev, VE_DEC_H265_STATUS) & VE_DEC_H265_STATUS_VLD_BUSY)
-			udelay(1);
+
+		if (cedrus_wait_for(dev, VE_DEC_H265_STATUS, VE_DEC_H265_STATUS_VLD_BUSY))
+			dev_err_ratelimited(dev->dev, "timed out waiting to skip bits\n");
 
 		count += tmp;
 	}
-- 
2.37.2