linux-kernel - Re: [PATCH v3 2.6.39-rc1-tip 6/26] 6: Uprobes: register/unregister probes.

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Date:	Fri, 1 Apr 2011 21:29:09 -0400
From:	Stephen Wilson <wilsons@...rt.ca>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Christoph Hellwig <hch@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	SystemTap <systemtap@...rces.redhat.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2.6.39-rc1-tip 6/26]  6: Uprobes:
	register/unregister probes.

On Sat, Apr 02, 2011 at 06:23:53AM +0530, Srikar Dronamraju wrote:
> > > +
> > > +		mm = vma->vm_mm;
> > > +		if (!valid_vma(vma)) {
> > > +			mmput(mm);
> > > +			continue;
> > > +		}
> > > +
> > > +		vaddr = vma->vm_start + offset;
> > > +		vaddr -= vma->vm_pgoff << PAGE_SHIFT;
> > 
> > What happens here when someone passes an offset that is out of bounds
> > for the vma?  Looks like we could oops when the kernel tries to set a
> > breakpoint.  Perhaps check wrt ->vm_end?
> > 
> 
> If the offset is wrong, install_uprobe will fail, since
> grab_cache_page() should not be able to find that page for us.
> And hence we return gracefully.

Hummm.  But grab_cache_page() just wraps find_or_create_page(), so I don't
think it will do what you want.


> I will surely test this case and I am happy to add a check for
> vm_end.

Thanks!


-- 
steve

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