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

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Message-ID: <20200930132958.GF29288@alley>
Date:   Wed, 30 Sep 2020 15:29:58 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
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 11:07:33, 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.
> 
> Fixes: f5f022e53b87 ("printk: reimplement log_cont using record extension")
> Signed-off-by: John Ogness <john.ogness@...utronix.de>
> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr