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List:       linux-kernel
Subject:    Re: [PATCH] Fix queued SIGIO
From:       Andi Kleen <ak () muc ! de>
Date:       2000-09-18 12:02:26
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On Mon, Sep 18, 2000 at 01:44:04PM +0200, Alan Cox wrote:
> > On Mon, Sep 18, 2000 at 12:34:03PM +0200, Alan Cox wrote:
> > > > The problem is really that SI_SIGIO is negative, but it should be positive
> > > > to make SI_FROMUSER return false on it. 
> > > > 
> > > > Changing it would unfortunately break binary compatibility. This patch
> > > 
> > > Why ?
> > 
> > If a program checks info->si_code for incoming signals.
> 
> ok now what does the value the kernel passes have to do with the value we
> write on the user stack - at the moment we blindly copy but we could just
> use a tiny lookup table to 'dekernelize' the ID. In fact if you picked a bitflag
> you could just mask it

That would not help much, the user could just still set the non mapped 
value in sigqueueinfo() [which would need to be forbidden to avoid
users faking kernel signals, which my patch exactly does] 


-Andi

-- 
This is like TV. I don't like TV.
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