linux-kernel - Re: [PATCH] Added PR_SET_PROCTITLE

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Date:	Mon,  5 Oct 2009 16:18:58 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Bryan Donlan <bdonlan@...il.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Timo Sirainen <tss@....fi>, linux-kernel@...r.kernel.org,
	Ulrich Drepper <drepper@...hat.com>
Subject: Re: [PATCH] Added PR_SET_PROCTITLE_AREA option for prctl()

> On Sun, Oct 4, 2009 at 11:29 PM, KOSAKI Motohiro
> <kosaki.motohiro@...fujitsu.com> wrote:
> >> On Sun, Oct 4, 2009 at 10:48 PM, KOSAKI Motohiro
> >> <kosaki.motohiro@...fujitsu.com> wrote:
> >>
> >> > +                       } else {
> >> > +                               len = mm->env_end - mm->env_start;
> >> > +                               if (len > PAGE_SIZE - res)
> >> > +                                       len = PAGE_SIZE - res;
> >> > +                               res += access_process_vm(task, mm->env_start,
> >> > +                                                        buffer+res, len, 0);
> >> > +                               res = strnlen(buffer, res);
> >> > +                       }
> >>
> >>
> >> This bug was in the original code, but since you're touching it
> >> anyway, it should be fixed now; if this access_process_vm fails
> >> (perhaps due to the target unmapping the page in question in between
> >> the two calls), bad things might happen if (error code) + res < 0, as
> >> then strnlen will get a huge value in its length (possibly leading to
> >> OOPS etc). It should be changed to check for an error return here and
> >> fail out properly if there is an error in this second check.
> >
> > AFAIK, access_process_vm() never return negative value.
> 
> Ahh, okay, I had read the if (res > 0 && ...) bit in the original code
> as an error test. Nevermind then.

No problem. very thak you for your good reviewing :)


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