linux-kernel - Re: [PATCH RESEND v4] checkpatch: add uninitialized pointer with _

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Message-ID: <f8b93a66-c755-497d-a425-c7b4baff5165@kernel.org>
Date: Sat, 22 Nov 2025 14:01:40 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ally Heev <allyheev@...il.com>, Dwaipayan Ray <dwaipayanray1@...il.com>,
 Lukas Bulwahn <lukas.bulwahn@...il.com>, Joe Perches <joe@...ches.com>,
 Jonathan Corbet <corbet@....net>, Andy Whitcroft <apw@...onical.com>
Cc: workflows@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, Dan Carpenter <dan.carpenter@...aro.org>,
 David Hunter <david.hunter.linux@...il.com>,
 Shuah Khan <skhan@...uxfoundation.org>, Viresh Kumar <vireshk@...nel.org>,
 Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
 linux-pm <linux-pm@...r.kernel.org>, dan.j.williams@...el.com,
 Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH RESEND v4] checkpatch: add uninitialized pointer with
 __free attribute check

On 17/11/2025 04:10, Ally Heev wrote:
> uninitialized pointers with __free attribute can cause undefined
> behavior as the memory randomly assigned to the pointer is freed
> automatically when the pointer goes out of scope.
> add check in checkpatch to detect such issues.
> 
> Suggested-by: Dan Carpenter <dan.carpenter@...aro.org>
> Link: https://lore.kernel.org/all/8a4c0b43-cf63-400d-b33d-d9c447b7e0b9@suswa.mountain/
> Acked-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Ally Heev <allyheev@...il.com>
> ---
> Testing:
> ran checkpatch.pl before and after the change on
> crypto/asymmetric_keys/x509_public_key.c, which has
> both initialized with NULL and uninitialized pointers
> ---
> Changes in v4:
> - fixed UNINITIALIZED_PTR_WITH_FREE description
> - Link to v3: https://lore.kernel.org/r/20251025-aheev-checkpatch-uninitialized-free-v3-1-a67f72b1c2bd@gmail.com
> 
> Changes in v3:
> - remove $FreeAttribute
> - Link to v2: https://lore.kernel.org/r/20251024-aheev-checkpatch-uninitialized-free-v2-0-16c0900e8130@gmail.com
> 
> Changes in v2:
> - change cover letter and title to reflect new changes
> - fix regex to handle multiple declarations in a single line case
> - convert WARN to ERROR for uninitialized pointers
> - add a new WARN for pointers initialized with NULL
> - NOTE: tried handling multiple declarations on a single line by splitting
>         them and matching the parts with regex, but, it turned out to be
> 	complex and overkill. Moreover, multi-line declarations pose a threat
> - Link to v1: https://lore.kernel.org/r/20251021-aheev-checkpatch-uninitialized-free-v1-1-18fb01bc6a7a@gmail.com
> ---
>  Documentation/dev-tools/checkpatch.rst | 5 +++++
>  scripts/checkpatch.pl                  | 6 ++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
> index d5c47e560324fb2399a5b1bc99c891ed1de10535..c61a3892a60c13f7c5ba89e969e39a93a3dcd5bc 100644
> --- a/Documentation/dev-tools/checkpatch.rst
> +++ b/Documentation/dev-tools/checkpatch.rst
> @@ -1009,6 +1009,11 @@ Functions and Variables
>  
>        return bar;
>  
> +  **UNINITIALIZED_PTR_WITH_FREE**
> +    Pointers with __free attribute should be initialized. Not doing so


I saw the other discussion and Linus re-iterated old approach/syntax
preference, thus I think this should also include it, since it is de
facto a coding style:

"Pointers with __free attribute should be declared in the place of use
and initialized (see include/linux/cleanup.h)......"

Best regards,
Krzysztof