linux-kernel - Re: [PATCH -tip 2/2] Pass mm->flags as a coredump parameter for consistency

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Date:	Thu, 19 Nov 2009 21:57:37 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Roland McGrath <roland@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH -tip 2/2] Pass mm->flags as a coredump parameter for	consistency

Hi Hiramatsu-san,

Masami Hiramatsu wrote:

>> Pass mm->flags as a coredump parameter for consistency.
>> 
>>  ---
>> 1787         if (mm->core_state || !get_dumpable(mm)) {  <- (1)
>> 1788                 up_write(&mm->mmap_sem);
>> 1789                 put_cred(cred);
>> 1790                 goto fail;
>> 1791         }
>> 1792
>> [...]
>> 1798         if (get_dumpable(mm) == 2) {    /* Setuid core dump mode */ <-(2)
>> 1799                 flag = O_EXCL;          /* Stop rewrite attacks */
>> 1800                 cred->fsuid = 0;        /* Dump root private */
>> 1801         }
>>  ---
>> 
>> Since dumpable bits are not protected by lock, there is a
>> chance to change these bits between (1) and (2).

Yes, a race condition can be caused by prctl from another thread.
And your patch is fine with me.  Thanks!

Reviewed-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
--
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

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