linux-kernel - Re: [PATCH 5/7] uprobes: Fix utask->xol_vaddr leak in pre

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Date:	Tue, 8 Jan 2013 18:44:47 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Josh Stone <jistone@...hat.com>,
	"Suzuki K. Poulose" <suzuki@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] uprobes: Fix utask->xol_vaddr leak in pre_ssout()

On 01/08, Srikar Dronamraju wrote:
>
> * Oleg Nesterov <oleg@...hat.com> [2012-12-31 18:52:26]:
>
> > pre_ssout() should do xol_free_insn_slot() if arch_uprobe_pre_xol()
> > fails, otherwise nobody will free the allocated slot.
> >
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
>
> Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

Thanks!

> (one nit below)
> ...
> > @@ -1316,7 +1317,13 @@ pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
> >  	utask->xol_vaddr = xol_vaddr;
> >  	utask->vaddr = bp_vaddr;
> >
> > -	return arch_uprobe_pre_xol(&uprobe->arch, regs);
> > +	err = arch_uprobe_pre_xol(&uprobe->arch, regs);
> > +	if (unlikely(err)) {
> > +		xol_free_insn_slot(current);
> > +		return err;
> > +	}
> > +
> > +	return 0;
> >  }
>
> Nit: we could reduce a line or two with
>
> 	err = arch_uprobe_pre_xol(&uprobe->arch, regs);
> 	if (unlikely(err))
> 		xol_free_insn_slot(current);
>
> 	return err;

Yes, but this is also preparation for the next patch which adds more
code after arch_uprobe_pre_xol() == 0.

Oleg.

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