linux-kernel - Re: [PATCH V4] Fix pointer cast for 32 bits arch

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Date:	Thu, 16 Apr 2015 20:01:44 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Peter Senna Tschudin <peter.senna@...il.com>,
	driverdevel <devel@...verdev.osuosl.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jun Tian <jun.j.tian@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andreas <schwab@...ux-m68k.org>,
	Garret Kelly <garret.kelly@...il.com>,
	Octavian Purdila <octavian.purdila@...el.com>,
	Nick Kralevich <nnk@...gle.com>, Alan <alan@...ux.intel.com>
Subject: Re: [PATCH V4] Fix pointer cast for 32 bits arch

On Thu, Apr 16, 2015 at 06:14:55PM +0200, Geert Uytterhoeven wrote:
> On Thu, Apr 16, 2015 at 3:39 PM, Peter Senna Tschudin
> <peter.senna@...il.com> wrote:
> > --- a/drivers/staging/goldfish/goldfish_audio.c
> > +++ b/drivers/staging/goldfish/goldfish_audio.c
> > @@ -63,7 +63,7 @@ struct goldfish_audio {
> >  #define AUDIO_READ(data, addr)         (readl(data->reg_base + addr))
> >  #define AUDIO_WRITE(data, addr, x)     (writel(x, data->reg_base + addr))
> >  #define AUDIO_WRITE64(data, addr, addr2, x)    \
> > -       (gf_write64((u64)(x), data->reg_base + addr, data->reg_base+addr2))
> > +       (gf_write_ptr((void *)(x), data->reg_base + addr, data->reg_base+addr2))
> 
> This one should not be converted, as all callers pass a dma_addr_t, which may
> be 64-bit on 32-bit systems, i.e. larger than void *.

Ugh...  You're right.

I've been avoiding asking this but I can't any longer.  What is
gf_write64() actually doing?  We are writing dma addresses, user space
pointers and kernel space pointers to this hardware?

This stuff doesn't seem to make any kind of sense and I can easily
imagine a situation where it wrote a 64 bit pointer.  Then we partially
write over it with a 32 bit userspace pointer.  Then it writes somewhere
totally unintended.

This thing doesn't make any sort of sense to me.

regards,
dan carpenter
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