Re: [PATCH next v2 1/2] printk: avoid and/or handle record truncation

[Joe Perches]

On Wed, 2020-09-30 at 11:07 +0206, John Ogness wrote:
> If a reader provides a buffer that is smaller than the message text,
> the @text_len field of @info will have a value larger than the buffer
> size. If readers blindly read @text_len bytes of data without
> checking the size, they will read beyond their buffer.
> 
> Add this check to record_print_text() to properly recognize when such
> truncation has occurred.
> 
> Add a maximum size argument to the ringbuffer function to extend
> records so that records can not be created that are larger than the
> buffer size of readers.
> 
> When extending records (LOG_CONT), do not extend records beyond
> LOG_LINE_MAX since that is the maximum size available in the buffers
> used by consoles and syslog.

I still think it better to support backspace by rewinding
the buffer rather than truncation of the output.