Re: [PATCH v2 1/2] checkpatch: add uninitialized pointer with __free attribute check

[Joe Perches <joe@perches.com>]

On Fri, 2025-10-24 at 22:59 +0530, Ally Heev wrote:
> uninitialized pointers with __free attribute can cause undefined
> behaviour as the memory allocated 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@linaro.org>
> Link: https://lore.kernel.org/all/8a4c0b43-cf63-400d-b33d-d9c447b7e0b9@suswa.mountain/
> Acked-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Ally Heev <allyheev@gmail.com>
> ---
>  Documentation/dev-tools/checkpatch.rst | 5 +++++
>  scripts/checkpatch.pl                  | 7 +++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
> index d5c47e560324fb2399a5b1bc99c891ed1de10535..1a304bf38bcd27e50bbb7cd4383b07ac54d20b0a 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
> +    may lead to undefined behavior as the memory allocated (garbage,
> +    in case not initialized) to the pointer is freed automatically
> +    when the pointer goes out of scope.
>  
>  Permissions
>  -----------
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 92669904eecc7a8d2afd3f2625528e02b6d17cd6..1009a4a065e910143dabeee6640b3b3a4bd3fe06 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -509,6 +509,7 @@ our $InitAttributeData = qr{$InitAttributePrefix(?:initdata\b)};
>  our $InitAttributeConst = qr{$InitAttributePrefix(?:initconst\b)};
>  our $InitAttributeInit = qr{$InitAttributePrefix(?:init\b)};
>  our $InitAttribute = qr{$InitAttributeData|$InitAttributeConst|$InitAttributeInit};
> +our $FreeAttribute = qr{__free\s*\(\s*$Ident\s*\)};

If you are really suggesting using this, and I don't think it's
particularly useful, please use

out $InitAttributeFree = qr{$InitAttributePrefix(?:free\s*\(\s*$Ident\s*\)};

>  
>  # Notes to $Attribute:
>  # We need \b after 'init' otherwise 'initconst' will cause a false positive in a check
> @@ -7721,6 +7722,12 @@ sub process {
>  				ERROR("MISSING_SENTINEL", "missing sentinel in ID array\n" . "$here\n$stat\n");
>  			}
>  		}
> +
> +# check for uninitialized pointers with __free attribute
> +		while ($line =~ /\*\s*($Ident)\s+$FreeAttribute\s*[,;]/g) {
> +			ERROR("UNINITIALIZED_PTR_WITH_FREE",
> +			      "pointer '$1' with __free attribute should be initialized\n" . $herecurr);
> +		}
>  	}
>  
>  	# If we have no input at all, then there is nothing to report on