linux-kernel - Re: [PATCH][Resend v2] Fix infinite loop in search_binary

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Message-Id: <201107041420.31049.richard@nod.at>
Date:	Mon, 4 Jul 2011 14:20:30 +0200
From:	Richard Weinberger <richard@....at>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	viro@...iv.linux.org.uk, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH][Resend v2] Fix infinite loop in search_binary_handler()

Am Montag 04 Juli 2011, 14:10:43 schrieb Tetsuo Handa:
> Richard Weinberger wrote:
> > Am Montag 04 Juli 2011, 13:51:55 schrieb Tetsuo Handa:
> > > Richard Weinberger wrote:
> > > > Running a x86_64 kernel without ia32 emulation and a x86 user land
> > > > triggers this issue.
> > > 
> > > Executing /sbin/modprobe for x86_32 on an x86_64 kernel without x86_32
> > > support?
> > 
> > Yep.
> > 
> > > Anyway, request_module() calls __request_module() but
> > > __request_module() stops at MAX_KMOD_CONCURRENT levels of nesting.
> > > So, I think "infinite loop" cannot happen.
> > 
> > Booting a x86_64 UML kernel with x86_32 user land triggers this issue.
> > I always wondered why the UML kernel hangs an consumes 100% CPU.
> 
> That's strange... Would you show us printk() output like
> 
> 	printk(KERN_INFO "Calling request_module()\n");
> 	request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
> 	printk(KERN_INFO "Returned from request_module()\n");
> 
> for demonstrating that __request_module() cannot stop at
> MAX_KMOD_CONCURRENT levels of nesting?

There you go!
http://userweb.kernel.org/~rw/boot.log

I did not count all messages, but they are more than 50. :-)

Thanks,
//richard
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