linux-kernel - Re: [PATCH] cpufreq: dt: fix oops on armada37xx

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Message-ID: <20200620191052.GA21708@mail.rc.ru>
Date:   Sat, 20 Jun 2020 20:10:52 +0100
From:   Ivan Kokshaysky <ink@...assic.park.msu.ru>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Gregory Clement <gregory.clement@...tlin.com>,
        Jason Cooper <jason@...edaemon.net>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: dt: fix oops on armada37xx

On Sat, Jun 20, 2020 at 07:54:38PM +0200, Andrew Lunn wrote:
> On Sat, Jun 20, 2020 at 05:44:49PM +0100, Ivan Kokshaysky wrote:
> > Commit 0c868627e617e43a295d8 (cpufreq: dt: Allow platform specific
> > intermediate callbacks) added two function pointers to the
> > struct cpufreq_dt_platform_data. However, armada37xx_cpufreq_driver_init()
> > has this struct (pdata) located on the stack and uses only "suspend"
> > and "resume" fields. So these newly added "get_intermediate" and
> > "target_intermediate" pointers are uninitialized and contain arbitrary
> > non-null values, causing all kinds of trouble.
> > 
> > For instance, here is an oops on espressobin after an attempt to change
> > the cpefreq governor:
> > 
> > [   29.174554] Unable to handle kernel execute from non-executable memory at virtual address ffff00003f87bdc0
> > ...
> > [   29.269373] pc : 0xffff00003f87bdc0
> > [   29.272957] lr : __cpufreq_driver_target+0x138/0x580
> > ...
> > 
> > Fixed by zeroing out pdata before use.
> > 
> > Signed-off-by: Ivan Kokshaysky <ink@...assic.park.msu.ru>
> 
> Hi Ivan
> 
> A Fixes: tag would be good.

Hi Andrew,

I'm not sure that "Fixes:" would be appropriate here - commit 0c868627e617
is fine by itself, it just revealed a bug in older code.

Thanks for reviewing,
Ivan.

> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> 
>     Andrew