Re: [PATCH RESEND v4] checkpatch: add uninitialized pointer with __free attribute check

[Krzysztof Kozlowski]

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@xxxxxxxxxx>
> Link: https://lore.kernel.org/all/8a4c0b43-cf63-400d-b33d-d9c447b7e0b9@suswa.mountain/
> Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> Signed-off-by: Ally Heev <allyheev@xxxxxxxxx>
> ---
> 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@xxxxxxxxx
> 
> Changes in v3:
> - remove $FreeAttribute
> - Link to v2: https://lore.kernel.org/r/20251024-aheev-checkpatch-uninitialized-free-v2-0-16c0900e8130@xxxxxxxxx
> 
> 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@xxxxxxxxx
> ---
>  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