linux-kernel - Re: [PATCH 4.19 216/220] PM / devfreq: Fix static checker warning in try_then_request

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Message-ID: <20191128075312.GA3362744@kroah.com>
Date:   Thu, 28 Nov 2019 08:53:12 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 216/220] PM / devfreq: Fix static checker warning in
 try_then_request_governor

On Thu, Nov 28, 2019 at 12:40:20PM +0900, Nobuhiro Iwamatsu wrote:
> Hi,
> 
> On Fri, Nov 22, 2019 at 11:29:41AM +0100, Greg Kroah-Hartman wrote:
> > From: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> > 
> > [ Upstream commit b53b0128052ffd687797d5f4deeb76327e7b5711 ]
> > 
> > The patch 23c7b54ca1cd: "PM / devfreq: Fix devfreq_add_device() when
> > drivers are built as modules." leads to the following static checker
> > warning:
> > 
> >     drivers/devfreq/devfreq.c:1043 governor_store()
> >     warn: 'governor' can also be NULL
> > 
> > The reason is that the try_then_request_governor() function returns both
> > error pointers and NULL. It should just return error pointers, so fix
> > this by returning a ERR_PTR to the error intead of returning NULL.
> > 
> > Fixes: 23c7b54ca1cd ("PM / devfreq: Fix devfreq_add_device() when drivers are built as modules.")
> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> > Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>
> > Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> > Signed-off-by: Sasha Levin <sashal@...nel.org>
> 
> The following commits are provided for this fix:
> 
> commit 7544fd7f384591038646d3cd9efb311ab4509e24
> Author: Ezequiel Garcia <ezequiel@...labora.com>
> Date:   Fri Jun 21 18:39:49 2019 -0300
> 
>     PM / devfreq: Fix kernel oops on governor module load
> 
>     A bit unexpectedly (but still documented), request_module may
>     return a positive value, in case of a modprobe error.
>     This is currently causing issues in the devfreq framework.
> 
>     When a request_module exits with a positive value, we currently
>     return that via ERR_PTR. However, because the value is positive,
>     it's not a ERR_VALUE proper, and is therefore treated as a
>     valid struct devfreq_governor pointer, leading to a kernel oops.
> 
>     Fix this by returning -EINVAL if request_module returns a positive
>     value.
> 
>     Fixes: b53b0128052ff ("PM / devfreq: Fix static checker warning in try_then_request_governor")
>     Signed-off-by: Ezequiel Garcia <ezequiel@...labora.com>
>     Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>
>     Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
> 
> Please apply.

Good catch, now queued up.

greg k-h