linux-kernel - Re: [PATCH] platform/x86: panasonic-laptop: fix NULL dereference

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Date: Fri, 29 Mar 2024 11:20:49 +0300
From: Maxim Korotkov <korotkov.maxim.s@...il.com>
To: Armin Wolf <W_Armin@....de>, Kenneth Chan <kenneth.t.chan@...il.com>,
 Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: Len Brown <len.brown@...el.com>,
 Henrique de Moraes Holschuh <hmh@....eng.br>,
 Harald Welte <laforge@...monks.org>, Matthew Garrett <mjg@...hat.com>,
 Ivan Kapranov <i.kapranov@...uritycode.ru>, lvc-project@...uxtesting.org,
 platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: panasonic-laptop: fix NULL dereference

Hi,
On 29.03.2024 03:21, Armin Wolf wrote:
>> Added a pointer check to ensure that it is valid
>> before using it for pcc initialization.
> 
> Hi,
> 
> is this check even needed? I think the ACPI driver core takes care
> of passing a valid ACPI device pointer to acpi_pcc_hotkey_remove().
> 
> Thanks,
> Armin Wolf

I proceeded from the assumption that the current check was not redundant.
Kuppuswamy correctly noted in the message that the device would most 
likely be valid for the function of removal.

However, in my opinion, checking for NULL is a good coding practice, and 
has now been implemented incorrectly in this case.

Eliminating NULL checks could potentially cause bugs in this context.

Best regards, Max