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From: Sasha Levin <levinsasha928@gmail.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Jones <davej@redhat.com>,
	kexec@lists.infradead.org,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: BUG: unable to handle kernel paging request at ffffc7ff81000398 (sys_kexec_load)
Date: Sat, 28 Jan 2012 10:11:30 -0500	[thread overview]
Message-ID: <1327763490.16907.1.camel@lappy> (raw)
In-Reply-To: <m1lip0s5nt.fsf@fess.ebiederm.org>

On Sat, 2012-01-21 at 20:49 -0800, Eric W. Biederman wrote:
> Interesting.
> 
> The fact that this happens in native_set_pte would suggest that we are
> trying to write to a page table that does not exist.  So this might
> be a layer below kexec_load that has the problem.
> 
> Do you have the kernel you were testing?    A disassembly of the
> native_set_pte, machine_kexec_prepare and sys_kexec_load
> would be interesting, for attempting to trace this back to what went
> wrong.

I did some work into investigating it today, looks like it's simple to trigger it using the following code:

	#include <fcntl.h>
	int main(void)
	{
		char dummy[4096] = {0};
		syscall(246, 0xffffffff81008000, 1, dummy, 2);
		return 0;
	}

I'll continue trying to figure out whats wrong, but hopefully this lead will help in reproducing it easily.

-- 

Sasha.


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WARNING: multiple messages have this Message-ID (diff)
From: Sasha Levin <levinsasha928@gmail.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Dave Jones <davej@redhat.com>,
	kexec@lists.infradead.org,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: BUG: unable to handle kernel paging request at ffffc7ff81000398 (sys_kexec_load)
Date: Sat, 28 Jan 2012 10:11:30 -0500	[thread overview]
Message-ID: <1327763490.16907.1.camel@lappy> (raw)
In-Reply-To: <m1lip0s5nt.fsf@fess.ebiederm.org>

On Sat, 2012-01-21 at 20:49 -0800, Eric W. Biederman wrote:
> Interesting.
> 
> The fact that this happens in native_set_pte would suggest that we are
> trying to write to a page table that does not exist.  So this might
> be a layer below kexec_load that has the problem.
> 
> Do you have the kernel you were testing?    A disassembly of the
> native_set_pte, machine_kexec_prepare and sys_kexec_load
> would be interesting, for attempting to trace this back to what went
> wrong.

I did some work into investigating it today, looks like it's simple to trigger it using the following code:

	#include <fcntl.h>
	int main(void)
	{
		char dummy[4096] = {0};
		syscall(246, 0xffffffff81008000, 1, dummy, 2);
		return 0;
	}

I'll continue trying to figure out whats wrong, but hopefully this lead will help in reproducing it easily.

-- 

Sasha.


  parent reply	other threads:[~2012-01-28 15:11 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-22  6:06 BUG: unable to handle kernel paging request at ffffc7ff81000398 (sys_kexec_load) Sasha Levin
2012-01-22  6:06 ` Sasha Levin
2012-01-22  4:49 ` Eric W. Biederman
2012-01-22  4:49   ` Eric W. Biederman
2012-01-22  7:18   ` Sasha Levin
2012-01-22  7:18     ` Sasha Levin
2012-01-28 15:11   ` Sasha Levin [this message]
2012-01-28 15:11     ` Sasha Levin
2012-01-28 20:54     ` Eric W. Biederman
2012-01-28 20:54       ` Eric W. Biederman

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