linux-kernel - Re: Re: [PATCH -tip ] [BUGFIX] kprobes: Move hash

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Message-ID: <20130321113957.GA2659@gmail.com>
Date:	Thu, 21 Mar 2013 12:39:57 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Timo Juhani Lindfors <timo.lindfors@....fi>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Nadia Yvette Chambers <nyc@...omorphy.com>,
	yrl.pp-manager.tt@...achi.com,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: Re: [PATCH -tip ] [BUGFIX] kprobes: Move hash_64() into
 .text.kprobe section


* Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:

> (2013/03/19 5:57), Timo Juhani Lindfors wrote:
> > Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> writes:
> >> Thank you for reporting!!
> > 
> > Thanks for fixing these! I spent some time trying to automate the
> > process of finding sensitive functions and eventually resorted into
> > booting a kvm instance with a minimal initrd to test every single
> > function in a clean and reproducible environment.
> > 
> > I found 7 more cases where calling register_kprobe() leads to an instant
> > kernel panic:
> > 
> > __flush_tlb_single
> > native_flush_tlb
> > native_safe_halt
> > native_set_pgd
> > native_set_pmd
> > native_set_pud
> > native_write_cr0
> 
> Ah, right and Great! these native_* things are too fundamental one.
> Hmm, curiously, those are defined as inline functions, and
> I also couldn't find some of those symbols even with your previous
> kconfig.
> 
> > You can see full kernel console output for each function at
> > http://lindi.iki.fi/lindi/linux/kprobes/panics_2013-03-18/
> 
> As you can see, your panic messages, most of them caused GFP.
> This may mean that int3 software exception must not happened
> on those sites. Not the recursive call.
> 
> Perhaps, I'd better add those native_* things into symbol-name
> based blacklist, instead of adding __kprobes, because those
> are not related to kprobes recursion.

Blacklists are not really good in general - it's easy for a symbol to be 
renamed and the blacklist misses them silently ...

symbol name and annotation should go hand in hand.

Thanks,

	Ingo
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