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From:   Jernej =?utf-8?B?xaBrcmFiZWM=?= <jernej.skrabec@gmail.com>
To:     Alessandro Zummo <a.zummo@towertech.it>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Samuel Holland <samuel@sholland.org>
Cc:     linux-arm-kernel@lists.infradead.org, linux-rtc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-sunxi@lists.linux.dev,
        Samuel Holland <samuel@sholland.org>
Subject: Re: [PATCH 1/2] rtc: sun6i: Prevent an out-of-bounds read
Date:   Thu, 05 Jan 2023 18:26:02 +0100
Message-ID: <8201852.NyiUUSuA9g@jernej-laptop>
In-Reply-To: <20221229184011.62925-1-samuel@sholland.org>
References: <20221229184011.62925-1-samuel@sholland.org>
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Dne =C4=8Detrtek, 29. december 2022 ob 19:40:10 CET je Samuel Holland napis=
al(a):
> If there is more than one parent clock in the devicetree, the
> driver sets .num_parents to a larger value than the number of array
> elements, which causes an out-of-bounds read in the clock framework.

Is there any DT with more than one parent? I think more fixes are needed if=
=20
this is the case.

Best regards,
Jernej

>=20
> Fix this by coercing the parent count to a Boolean value, like the
> driver expects.
>=20
> Fixes: 3855c2c3e546 ("rtc: sun6i: Expose the 32kHz oscillator")
> Signed-off-by: Samuel Holland <samuel@sholland.org>
> ---
>=20
>  drivers/rtc/rtc-sun6i.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
> index ed5516089e9a..a22358a44e32 100644
> --- a/drivers/rtc/rtc-sun6i.c
> +++ b/drivers/rtc/rtc-sun6i.c
> @@ -294,7 +294,7 @@ static void __init sun6i_rtc_clk_init(struct device_n=
ode
> *node,
>=20
>  	init.parent_names =3D parents;
>  	/* ... number of clock parents will be 1. */
> -	init.num_parents =3D of_clk_get_parent_count(node) + 1;
> +	init.num_parents =3D !!of_clk_get_parent_count(node) + 1;
>  	of_property_read_string_index(node, "clock-output-names", 0,
>  				      &init.name);