linux-kernel - Re: [PATCH] printk: fix buffer overflow potential for print

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Message-ID: <yt9d1reayal2.fsf@linux.ibm.com>
Date:   Sun, 24 Jan 2021 09:59:21 +0100
From:   Sven Schnelle <svens@...ux.ibm.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: fix buffer overflow potential for print_text()

John Ogness <john.ogness@...utronix.de> writes:

> Hi Sven,
>
> Thanks for the outstanding analysis!
>
> On 2021-01-23, Sven Schnelle <svens@...ux.ibm.com> wrote:
>>> 1401		if (buf_size > 0)
>>> 1402			text[len] = 0;
>>
>> I don't think i have really understood how all the printk magic works,
>> but using r->text_buf[len] seems to be the correct place to put the
>> zero byte in that case?
>
> Yes, you are correct! @text is pointing to the beginning of the
> currently processed line, not the beginning of the buffer.
>
> I will submit a patch to fix our recent fix (unless you would like to do
> that).

Please go ahead, thank you!