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

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Message-ID: <YAa0j9CG/6yrGcs+@jagdpanzerIV.localdomain>
Date:   Tue, 19 Jan 2021 19:29:35 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...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 (21/01/19 10:00), John Ogness wrote:
> 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.

Any chance you can put those tests somewhere public so that we can
run them regularly? (say, before Petr sends out a pull request to
Linus.)

> 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.

Sure.

> One positive effect of the rework is that we are finding these oddities
> and documenting them.

Absolutely agree.

	-ss