linux-kernel - Re: [PATCH] opp: core: Check for pending links before reading required

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Message-ID: <20210823071538.bgfkym7emlq6d7oh@vireshk-i7>
Date:   Mon, 23 Aug 2021 12:45:38 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Pavel Dubrova <pashadubrova@...il.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] opp: core: Check for pending links before reading
 required_opp pointers

On 22-08-21, 19:44, Marijn Suijten wrote:
> Commit 4fa82a87ba55 ("opp: Allow required-opps to be used for non genpd
> use cases") dereferences the pointers in required_opp_tables but these
> might be set to an ERR_PTR if the list still has lazy links pending,
> resulting in segfaults.  Prior to this patch IS_ERR was also checked on
> required_opp_tables[i] before reading ->is_genpd inside
> _opp_table_alloc_required_tables, which is at the same time the
> predicate to add this table to the lazy list.  This segfault is solved
> by reordering the checks to bail on lazy pending tables before reading
> ->is_genpd.
> 
> Fixes: 4fa82a87ba55 ("opp: Allow required-opps to be used for non genpd use cases")
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
> ---
>  drivers/opp/core.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index b335c077f215..4dd26a165c91 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -893,6 +893,10 @@ static int _set_required_opps(struct device *dev,
>  	if (!required_opp_tables)
>  		return 0;
>  
> +	/* required-opps not fully initialized yet */
> +	if (lazy_linking_pending(opp_table))
> +		return -EBUSY;
> +
>  	/*
>  	 * We only support genpd's OPPs in the "required-opps" for now, as we
>  	 * don't know much about other use cases. Error out if the required OPP
> @@ -903,10 +907,6 @@ static int _set_required_opps(struct device *dev,
>  		return -ENOENT;
>  	}
>  
> -	/* required-opps not fully initialized yet */
> -	if (lazy_linking_pending(opp_table))
> -		return -EBUSY;
> -
>  	/* Single genpd case */
>  	if (!genpd_virt_devs)
>  		return _set_required_opp(dev, dev, opp, 0);

Applied. Thanks.

-- 
viresh