linux-kernel - Re: [PATCH] coredump_filter: enable to change the default filter

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Message-ID: <494B71D6.3080602@hitachi.com>
Date:	Fri, 19 Dec 2008 19:05:10 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	linux-kernel@...r.kernel.org, yumiko.sugita.yf@...achi.com,
	satoshi.oshima.fk@...achi.com
Subject: Re: [PATCH] coredump_filter: enable to change the default filter

Hi,

Roland McGrath wrote:

>>Or does the patch change other behaviour?  Say, when mm_init() is
>>called by a kernel thread (current->mm==NULL)?  call_usermodehelper(),
>>for example?
>>
>>If so, then setting init's filter doesn't cover that case.
> 
> Hmm, probably for the kernel thread case mm_init should use
> task_active_pid_ns(current)->child_reaper->mm->flags.

It makes sense.  It also enables us to change coredump_filter for
user mode helpers after the system was booted.

However, we would need a special care for PID namespace if we use
init's coredump_filter as default.  For a process with new PID
namespace and new /proc, writing to /proc/1/coredump_filter doesn't
mean changing default, although it's not a usual operation.

The reason why I suggested the boot parameter way is most users
can change the default easily.  Some users have difficulty to
change init scripts for various reasons.

So I think the boot parameter way is simpler for both users and
kernel developers.

Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

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