linux-kernel - Re: [PATCH] printk: fix discarding message when recursion

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Message-ID: <494C1D20.9000008@ct.jp.nec.com>
Date:	Fri, 19 Dec 2008 14:16:00 -0800
From:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Toshikazu Nakayama <nakayama.ts@...s.nec.co.jp>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: fix discarding message when recursion_bug

Ingo Molnar wrote:
> * Hiroshi Shimamoto <h-shimamoto@...jp.nec.com> wrote:
> 
>> From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
>>
>> Impact: fix
>>
>> When recursion_bug is true, kernel discards original message because printk_buf
>> contains recursion_bug_msg with NULL terminator. The sizeof(recursion_bug_msg)
>> makes this, use strlen() to get correct length without NULL terminator.
>>
>> Reported-by: Toshikazu Nakayama <nakayama.ts@...s.nec.co.jp>
>> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
>> ---
>>  kernel/printk.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> Good one - applied to tip/core/printk, thanks!
> 
> Btw., i'm curious: in what situation was such recursion observed, and how 
> did the kernel behave? You saw a truncated recursion message in dmesg - or 
> was it worse?

I'm not sure about the real situation. I've heard this issue was found in
printing messages in NMI handler, maybe with artificial kernel stuck.

Thanks,
Hiroshi
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