linux-kernel - Re: [PATCH 1/1] printk: fix syslog_print

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Message-ID: <87sg6uq1yl.fsf@jogness.linutronix.de>
Date:   Thu, 21 Jan 2021 06:49:46 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] printk: fix syslog_print_all() 1024-byte edge case

On 2021-01-20, John Ogness <john.ogness@...utronix.de> wrote:
> If klogctl(SYSLOG_ACTION_READ_ALL) is called with a buffer size
> of 1024 and the message data will exactly fill 1024 bytes and the
> last message of that is multi-line, the last line of the last
> message will be silently dropped.

Sorry, please disregard this patch. The problem is not because of the
size-1 behavior of record_print_text(). It is because syslog_print_all()
is allocating a temp buffer that is not large enough to hold multi-line
syslog-expanded records.

That problem can be solved another day, if we even want to consider it a
problem.

Sorry for the noise.

John Ogness