linux-kernel - Re: is avoiding compat ioctls possible?

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Message-ID: <alpine.DEB.2.00.0910280353080.19088@skynet.skynet.ie>
Date:	Wed, 28 Oct 2009 03:54:34 +0000 (GMT)
From:	Dave Airlie <airlied@...ux.ie>
To:	David Miller <davem@...emloft.net>
cc:	dri-devel@...ts.sourceforge.net, andi@...stfloor.org,
	linux-kernel@...r.kernel.org, arnd@...db.de
Subject: Re: is avoiding compat ioctls possible?

> 
> > we already opencoded this (probably before it was macroisied or we just 
> > pasted it), so the radeon one is buggy, I should just go and compat_* all 
> > of these then and we should be all happy?
> 
> It should be, it's only working because:
> 
> 1) A malicious userland hasn't put garbage in the upper bits for
>    you yet.
> 
> 2) Nobody has tested s390 yet :-)
> 

So will an inline like this work?

static inline void *__user convert_user_ptr(uint64_t ioctl_ptr)
{
#ifdef CONFIG_COMPAT
	if (is_compat_task())
		return compat_ptr((compat_uptr_t)ioctl_ptr);
	else
#endif
		return (void __user *)(unsigned long)ioctl_ptr;
}

then I can convert all the code to just use that instead of explicity 
casts or brokenness.

Dave.
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