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Message-ID: <b4c2ea7ec34aaf05d53264b19a6c40245ed361c0.camel@perches.com>
Date: Wed, 30 Sep 2020 08:25:24 -0700
From: Joe Perches <joe@...ches.com>
To: John Ogness <john.ogness@...utronix.de>,
Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Marek Szyprowski <m.szyprowski@...sung.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH next v2 1/2] printk: avoid and/or handle record
truncation
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.
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