linux-kernel - Re: [PATCH] printk: don't unconditionally shortcut print

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Message-ID: <89a20c81-1def-8f09-8259-3ba552f10981@i-love.sakura.ne.jp>
Date:   Tue, 4 Dec 2018 00:00:22 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: don't unconditionally shortcut print_time()

On 2018/12/03 23:14, Petr Mladek wrote:
> Well, IMHO, it does not explain the pagefault above. The copy_to_user()
> could come either from syslog_print() or from syslog_print_all(). They
> both have their own checks that prevent the buf overflow.
> 
> The code is tricky but it looks safe now. Is it possible that
> the crash was with some old, still broken, code? Or did you
> add some extra changes that you used to trigger a testing
> scenario?

I think I was using unmodified current linux.git, but I failed to save
the reproducer because I was editing under /tmp directory which does not
create a backup.

Anyway, after this patch, no problem is occurring.