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From:   Justin Capella <justincapella@gmail.com>
Date:   Fri, 27 Dec 2019 17:48:39 -0800
Message-ID: <CAMrEMU_QfP2fyh6HHf-QXAY=2GktQRaf1z0HPEX=TUcZQoY0Jw@mail.gmail.com>
Subject: Re: [PATCH AUTOSEL 4.9 25/38] rfkill: Fix incorrect check to avoid
 NULL pointer dereference
To:     Sasha Levin <sashal@kernel.org>, Aditya Pakki <pakki001@umn.edu>
Cc:     LKML <linux-kernel@vger.kernel.org>, stable@vger.kernel.org,
        Johannes Berg <johannes.berg@intel.com>,
        linux-wireless@vger.kernel.org, netdev@vger.kernel.org
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Should the mutex be held during this check? Do you know if any of the
users need changing to IS_ERR_OR_NULL or should the dev member also be
checked?

I'm not sure if this is true of the BUG_ON macros but I have seen
implementations of similar macros that are used in the conditional
avoiding the need for a 2nd check.

On Fri, Dec 27, 2019 at 10:18 AM Sasha Levin <sashal@kernel.org> wrote:
>
> From: Aditya Pakki <pakki001@umn.edu>
>
> [ Upstream commit 6fc232db9e8cd50b9b83534de9cd91ace711b2d7 ]
>
> In rfkill_register, the struct rfkill pointer is first derefernced
> and then checked for NULL. This patch removes the BUG_ON and returns
> an error to the caller in case rfkill is NULL.
>
> Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> Link: https://lore.kernel.org/r/20191215153409.21696-1-pakki001@umn.edu
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  net/rfkill/core.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/rfkill/core.c b/net/rfkill/core.c
> index 884027f62783..87c35844d7d9 100644
> --- a/net/rfkill/core.c
> +++ b/net/rfkill/core.c
> @@ -940,10 +940,13 @@ static void rfkill_sync_work(struct work_struct *work)
>  int __must_check rfkill_register(struct rfkill *rfkill)
>  {
>         static unsigned long rfkill_no;
> -       struct device *dev = &rfkill->dev;
> +       struct device *dev;
>         int error;
>
> -       BUG_ON(!rfkill);
> +       if (!rfkill)
> +               return -EINVAL;
> +
> +       dev = &rfkill->dev;
>
>         mutex_lock(&rfkill_global_mutex);
>
> --
> 2.20.1
>