Re: [PATCH] powerpc/rtas_flash: Use scnprintf() in rtas_flash_read_num()

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 22/07/26 21:58, Thorsten Blum wrote:
> Use scnprintf() and its return value to avoid a separate strlen() call.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
>   arch/powerpc/kernel/rtas_flash.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c
> index 583dc16e9d3c..aff8a67e274f 100644
> --- a/arch/powerpc/kernel/rtas_flash.c
> +++ b/arch/powerpc/kernel/rtas_flash.c
> @@ -291,6 +291,7 @@ static ssize_t rtas_flash_read_num(struct file *file, char __user *buf,
>   {
>   	struct rtas_update_flash_t *const uf = &rtas_update_flash_data;
>   	char msg[RTAS_MSG_MAXLEN];
> +	size_t len;
>   	int status;
>   
>   	mutex_lock(&rtas_update_flash_mutex);
> @@ -298,8 +299,8 @@ static ssize_t rtas_flash_read_num(struct file *file, char __user *buf,
>   	mutex_unlock(&rtas_update_flash_mutex);
>   
>   	/* Read as number */
> -	sprintf(msg, "%d\n", status);
> -	return simple_read_from_buffer(buf, count, ppos, msg, strlen(msg));
> +	len = scnprintf(msg, sizeof(msg), "%d\n", status);
> +	return simple_read_from_buffer(buf, count, ppos, msg, len);


Though there is no real buffer overflow issue here, it is a good idea to
convert sprintf to scnprintf. This change helps avoid calling strlen on the
same buffer.

Changes looks good to me. Feel free to add:
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>


>   }
>   
>   /* We could be much more efficient here.  But to keep this function