Subject: Re: select() for delay.
From: Steven Rostedt <rostedt@goodmis.org>
To: Arjan van de Ven <arjan@infradead.org>
Cc: madhu.subbaiah@wipro.com, linux-kernel@vger.kernel.org
In-Reply-To: <1130160451.2775.8.camel@laptopd505.fenrus.org>
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	 <1130160451.2775.8.camel@laptopd505.fenrus.org>
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Organization: Kihon Technologies
Date: Mon, 24 Oct 2005 09:37:52 -0400
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On Mon, 2005-10-24 at 15:27 +0200, Arjan van de Ven wrote:
> On Mon, 2005-10-24 at 09:18 -0400, Steven Rostedt wrote:
> > Hi Maduhu,
> > 
> > On Mon, 2005-10-24 at 16:25 +0530, madhu.subbaiah@wipro.com wrote:
> > 
> > > +                        put_user(sec, &tvp->tv_sec);
> > > +                        put_user(usec, &tvp->tv_usec);
> > 
> > I won't comment on the rest of the patch, but this part is definitely
> > wrong.  The pointer tvp is a user space address and once you dereference
> > that pointer to get to tv_sec, you can have a fault, which might
> > segfault the
> 
> &pointer->member  doesn't dereference the pointer, it just adds the
> offset of "member" to the content of the pointer.
> 

Oh crap! You're right ;-)

Argh, that's what I get for replying before my first cup of coffee and
suffering jet lag.

I should have known this since I just copied over the container_of macro
to a user process, and if what I said was true, ((type *)0)->member
would never work.

Oh well, time to wake up :-)

-- Steve


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