linux-kernel - Re: [PATCH 1/2] rtc: sun6i: Prevent an out-of-bounds read

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Message-ID: <8201852.NyiUUSuA9g@jernej-laptop>
Date:   Thu, 05 Jan 2023 18:26:02 +0100
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Samuel Holland <samuel@...lland.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...ts.linux.dev,
        Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH 1/2] rtc: sun6i: Prevent an out-of-bounds read

Dne četrtek, 29. december 2022 ob 19:40:10 CET je Samuel Holland napisal(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 
this is the case.

Best regards,
Jernej

> 
> Fix this by coercing the parent count to a Boolean value, like the
> driver expects.
> 
> Fixes: 3855c2c3e546 ("rtc: sun6i: Expose the 32kHz oscillator")
> Signed-off-by: Samuel Holland <samuel@...lland.org>
> ---
> 
>  drivers/rtc/rtc-sun6i.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> 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_node
> *node,
> 
>  	init.parent_names = parents;
>  	/* ... number of clock parents will be 1. */
> -	init.num_parents = of_clk_get_parent_count(node) + 1;
> +	init.num_parents = !!of_clk_get_parent_count(node) + 1;
>  	of_property_read_string_index(node, "clock-output-names", 0,
>  				      &init.name);