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

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Message-ID: <20110402005353.GA17416@linux.vnet.ibm.com>
Date:	Sat, 2 Apr 2011 06:23:53 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Stephen Wilson <wilsons@...rt.ca>
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.

> > +
> > +		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.

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

-- 
Thanks and Regards
Srikar
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