Re: [PATCH 10/28] of/fdt: Replace strlcat() with snprintf() in early_init_dt_scan_chosen()

[Rob Herring]

On Tue, Sep 15, 2026 at 08:18:27AM +0000, Bill Wendling wrote:
> When CONFIG_CMDLINE_EXTEND is enabled, early_init_dt_scan_chosen() uses
> two strlcat() calls to append a space and CONFIG_CMDLINE to the command
> line buffer.
> 
> In preparation for removing the deprecated strlcat() API[1], replace the
> strlcat() calls with a single snprintf() call using the existing string
> length.
> 
> Additionally, check for a NULL initial_boot_params pointer and jump to
> "handle_cmdline" so that CONFIG_CMDLINE handling still occurs without
> dereferencing a NULL FDT pointer in fdt_path_offset().
> 
> Link: https://github.com/KSPP/linux/issues/370 [1]
> Cc: codemender-patching+linux@xxxxxxxxxx
> Assisted-by: Assistant:Claude-3.5-Sonnet [editor_update_file, shell_command_run]
> Signed-off-by: Bill Wendling <morbo@xxxxxxxxxx>
> ---

> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index a64afc3ded3d..311021a83f03 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1095,6 +1095,9 @@ int __init early_init_dt_scan_chosen(char *cmdline)
>  	const void *rng_seed;
>  	const void *fdt = initial_boot_params;
>  
> +	if (!fdt)
> +		goto handle_cmdline;
> +
>  	node = fdt_path_offset(fdt, "/chosen");
>  	if (node < 0)
>  		node = fdt_path_offset(fdt, "/chosen@0");
> @@ -1133,8 +1136,12 @@ int __init early_init_dt_scan_chosen(char *cmdline)
>  	 */
>  #ifdef CONFIG_CMDLINE
>  #if defined(CONFIG_CMDLINE_EXTEND)
> -	strlcat(cmdline, " ", COMMAND_LINE_SIZE);
> -	strlcat(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
> +	{

No need for brackets.

> +		size_t len = strlen(cmdline);
> +
> +		if (len < COMMAND_LINE_SIZE)
> +			snprintf(cmdline + len, COMMAND_LINE_SIZE - len, " %s", CONFIG_CMDLINE);
> +	}
>  #elif defined(CONFIG_CMDLINE_FORCE)
>  	strscpy(cmdline, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
>  #else
> -- 
> 2.55.0.1032.g73a4cd73de-goog
>