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

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Message-ID: <87r1mh5mso.fsf@jogness.linutronix.de>
Date:   Tue, 19 Jan 2021 10:00:47 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        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>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: fix buffer overflow potential for print_text()

On 2021-01-19, Sergey Senozhatsky <sergey.senozhatsky@...il.com> wrote:
> John, how did you spot these problems?

I am preparing my series to remove the logbuf_lock, which also refactors
and consolidates code from syslog_print_all() and
kmsg_dump_get_buffer(). While testing/verifying my series, I noticed the
these oddities in the semantics and decided I should research where they
came from and if they were actually necessary.

I wouldn't say the oddities are necessary (in fact, they are quite
annoying), but we have decided to keep them in out of fear of breaking
out-of-tree modules and/or interesting userspace code.

One positive effect of the rework is that we are finding these oddities
and documenting them. I think you and Petr are going down a similar path
with the console registration stuff now.

John