From: Tom Zanussi <zanussi@us.ibm.com>
To: fche@redhat.com (Frank Ch. Eigler)
Cc: Tom Zanussi <zanussi@us.ibm.com>,
ltt-dev@shafik.org, systemtap@sources.redhat.com
Subject: Re: double fault -> PAGE_KERNEL flagged memory
Date: Wed, 23 Nov 2005 22:18:00 -0000 [thread overview]
Message-ID: <17284.60038.184453.258672@tut.ibm.com> (raw)
In-Reply-To: <y0mek57f5bs.fsf@tooth.toronto.redhat.com>
Frank Ch. Eigler writes:
>
> zanussi wrote:
>
> > [...] What would cause a double fault would be if the vmalloc_fault
> > tried logging before the page table was updated, which would cause
> > the same vmalloc fault.
>
> Then this is analogous to the problem of calling printk from within an
> inconveniently placed kprobe. What can we do to eliminate this
> vulnerability? Can we somehow arrange to "fault in" all probe-related
> kernel-space vmalloc areas into new process' address spaces, so we don't
> encounter this unintentional and undesirable reentrancy?
>
I'll think about it, but it doesn't sound like fun. It sounds like it
might be one of those cases where you only allow a tapset to
instrument a certain area, in this case a page fault tapset to
instrument the page fault path. I can't remember, how is the
possibility of a printk() in a problematic function currently handled
in systemtap?
Tom
next prev parent reply other threads:[~2005-11-23 22:18 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-22 1:12 double fault Stone, Joshua I
2005-11-22 1:25 ` Roland McGrath
2005-11-22 9:29 ` Richard J Moore
2005-11-22 14:00 ` double fault -> PAGE_KERNEL flagged memory Mathieu Desnoyers
2005-11-22 15:12 ` Tom Zanussi
2005-11-22 15:24 ` Mathieu Desnoyers
2005-11-22 16:52 ` Tom Zanussi
2005-11-22 18:59 ` Mathieu Desnoyers
2005-11-23 15:13 ` Tom Zanussi
2005-11-23 17:53 ` Mathieu Desnoyers
2005-11-23 20:16 ` Tom Zanussi
2005-11-23 21:00 ` Frank Ch. Eigler
2005-11-23 21:51 ` Roland McGrath
2005-11-23 21:56 ` Mathieu Desnoyers
2005-11-23 22:34 ` Roland McGrath
2005-11-23 22:44 ` Mathieu Desnoyers
2005-11-23 23:20 ` Tom Zanussi
2005-11-24 18:10 ` Frank Ch. Eigler
2005-11-24 22:09 ` Roland McGrath
2005-11-23 22:18 ` Tom Zanussi [this message]
2005-11-23 22:25 ` Frank Ch. Eigler
2005-11-23 23:21 ` Mathieu Desnoyers
2005-11-22 15:17 ` Mathieu Desnoyers
2005-11-22 15:42 ` Frank Ch. Eigler
2005-11-22 16:01 ` Mathieu Desnoyers
2005-11-23 8:34 ` double fault Martin Hunt
2005-11-23 17:21 ` Mathieu Desnoyers
2005-11-23 17:54 ` Martin Hunt
2005-11-23 18:09 ` Mathieu Desnoyers
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