Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Jernej =?utf-8?B?xaBrcmFiZWM=?= <jernej.skrabec@gmail.com>
To:     linux-media@vger.kernel.org, Maxime Ripard <mripard@kernel.org>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Samuel Holland <samuel@sholland.org>,
        Nicolas Dufresne <nicolas.dufresne@collabora.com>
Cc:     kernel@collabora.com,
        Dmitry Osipenko <dmitry.osipenko@collabora.com>,
        stable@vger.kernel.org,
        Nicolas Dufresne <nicolas.dufresne@collabora.com>,
        linux-staging@lists.linux.dev,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 3/3] media: cedrus: Fix endless loop in cedrus_h265_skip_bits()
Date:   Fri, 19 Aug 2022 06:16:12 +0200
Message-ID: <5849126.lOV4Wx5bFT@jernej-laptop>
In-Reply-To: <20220818203308.439043-4-nicolas.dufresne@collabora.com>
References: <20220818203308.439043-1-nicolas.dufresne@collabora.com> <20220818203308.439043-4-nicolas.dufresne@collabora.com>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Dne =C4=8Detrtek, 18. avgust 2022 ob 22:33:08 CEST je Nicolas Dufresne napi=
sal(a):
> From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
>=20
> 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.
>=20
> Cc: stable@vger.kernel.org
> Reported-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>

=46ixes tag would be nice.

> ---
>  drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>=20
> 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 =3D 0;
> +	u32 reg;
>=20
>  	while (count < num) {
>  		int tmp =3D 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)) +		=09
dev_err_ratelimited(dev->dev, "timed out
> waiting to skip bits\n");

Reporting issue is nice, but better would be to propagate error, since ther=
e=20
is no way to properly decode this slice if above code block fails.

Best regards,
Jernej

>=20
>  		count +=3D tmp;
>  	}