Re: [PATCH v2 1/3] Doc: deprecated.rst: add strlcat()

[Kees Cook]

On Thu, May 14, 2026 at 06:26:53PM +0200, Manuel Ebner wrote:
> add strlcat and alternatives
> 
> Signed-off-by: Manuel Ebner <manuelebner@xxxxxxxxxxx>
> ---
>  Documentation/process/deprecated.rst | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
> index fed56864d036..06e802f4bbfd 100644
> --- a/Documentation/process/deprecated.rst
> +++ b/Documentation/process/deprecated.rst
> @@ -153,6 +153,13 @@ used, and the destinations should be marked with the `__nonstring
>  attribute to avoid future compiler warnings. For cases still needing
>  NUL-padding, strtomem_pad() can be used.
>  
> +strlcat()
> +---------
> +strlcat() must re-scan the destination string from the beginning on each
> +call (O(n^2) behavior). Alternatives are seq_buf_puts() and seq_buf_printf().
> +snprintf(), scnprintf() and sysfs_emit() are possible aswell, but the adoption
> +of the arguments needs to be taken care off.
> +

How about just:

strlcat() must re-scan the destination string from the beginning on each
call (O(n^2) behavior). Use the seq_buf API or similar instead.


>  strlcpy()
>  ---------
>  strlcpy() reads the entire source buffer first (since the return value
> -- 
> 2.54.0
> 

-- 
Kees Cook