linux-kernel - Re: [PATCH 5/7] uretprobes: return probe exit, invoke handlers

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Date:	Mon, 25 Mar 2013 13:31:21 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Anton Arapov <anton@...hat.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Josh Stone <jistone@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	adrian.m.negreanu@...el.com, Torsten.Polle@....de
Subject: Re: [PATCH 5/7] uretprobes: return probe exit, invoke handlers

The last comment, I promise ;)

On 03/24, Oleg Nesterov wrote:
>
> On 03/22, Anton Arapov wrote:
> >
> > +static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
> > +{
> > +	struct uprobe_task *utask;
> > +	struct return_instance *ri, *tmp;
> > +	unsigned long prev_ret_vaddr;
> > +
> > +	utask = get_utask();
> > +	if (!utask)
> > +		return;
> > +
> > +	ri = utask->return_instances;
> > +	if (!ri)
> > +		return;
>
> Hmm. I am wondering what should the caller (handle_swbp) do in this
> case...

And you do not actually need get_utask(), just check current->utask.

handle_uretprobe() must not be called if either ->utask or
->return_instances is NULL. This can only happen if we have a bug,
or user-space tries to fool the kernel.

Perhaps it makes sense to add pr_warn().

Oleg.

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