linux-kernel - Re: [PATCH] PM / devfreq: return PTR_ERR not NULL in try_then_request

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Date:   Wed, 24 Apr 2019 10:23:54 +0200
From:   Enric Balletbo Serra <eballetbo@...il.com>
To:     Steven Price <steven.price@....com>
Cc:     Kyungmin Park <kyungmin.park@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] PM / devfreq: return PTR_ERR not NULL in try_then_request_governor()

Hi,

Missatge de Steven Price <steven.price@....com> del dia dc., 3 d’abr.
2019 a les 17:26:

>
> The callers of try_then_request_governor() only test for a PTR_ERR using
> IS_ERR(). However in the case that request_module() fails then NULL is
> currently returned which will cause a NULL-pointer dereference in the
> caller.
>
> Instead convert the error we already have to a valid PTR_ERR and return
> it.
>
> Fixes: 23c7b54ca1cd ("PM / devfreq: Fix devfreq_add_device() when drivers are built as modules.")
> Signed-off-by: Steven Price <steven.price@....com>

There is already a fix for that. The fix was initially sent in October [2] but
unfortunately, it got lost. I resend and now is queued [1]. Hopefully, the Fixes
tag will help to pick the fix to the proper kernel releases.

Thanks,
 Enric

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/mzx/devfreq.git/commit/?h=for-next&id=b53b0128052ffd687797d5f4deeb76327e7b5711
[2] https://lkml.org/lkml/2018/10/16/744


> ---
>  drivers/devfreq/devfreq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0ae3de76833b..d29f66f0e52a 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -254,7 +254,7 @@ static struct devfreq_governor *try_then_request_governor(const char *name)
>                 /* Restore previous state before return */
>                 mutex_lock(&devfreq_list_lock);
>                 if (err)
> -                       return NULL;
> +                       return ERR_PTR(err);
>
>                 governor = find_devfreq_governor(name);
>         }
> --
> 2.20.1
>