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From: jacopo mondi <jacopo@jmondi.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jacopo Mondi <jacopo+renesas@jmondi.org>,
	ysato@users.sourceforge.jp, dalias@libc.org,
	thomas.petazzoni@free-electrons.com, robin.murphy@arm.com,
	geert@linux-m68k.org, linux-renesas-soc@vger.kernel.org,
	linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sh: mm: Fix unprotected access to struct device
Date: Wed, 18 Apr 2018 15:13:14 +0200	[thread overview]
Message-ID: <20180418131314.GC3999@w540> (raw)
In-Reply-To: <20180418104703.GA12462@infradead.org>

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Hi Christoph,

On Wed, Apr 18, 2018 at 03:47:03AM -0700, Christoph Hellwig wrote:
> On Tue, Apr 17, 2018 at 03:35:23PM +0200, Jacopo Mondi wrote:
> > With commit ce88313069c36eef80f21fd7 ("arch/sh: make the DMA mapping
> > operations observe dev->dma_pfn_offset") the generic DMA allocation
> > function on which the SH 'dma_alloc_coherent()' function relies on,
> > access the 'dma_pfn_offset' field of struct device.
> >
> > Unfortunately the 'dma_generic_alloc_coherent()' function is called from
> > several places with a NULL struct device argument, halting the CPU
> > during the boot process.
> >
> > This patch fixes the issue protecting access to dev->dma_pfn_offset,
> > with a trivial check for validity. It also passes a valid 'struct device'
> > in the 'platform_resource_setup_memory' function which is the main user
> > of 'dma_alloc_coherent()', and inserting a WARN_ON() check to make future
> > (and existing) bogus users of this function they're should provide a valid
> > 'struct device' whenever possible.
>
> Please fix those callers to not pass a NULL pointer instead.

As long as it goes for arch/sh, the only user of dma_alloc_coherent()
is platform_resource_setup_memory(), and it has been fixed by this
patch.

Unfortunately, as Thomas pointed out, there are drivers which calls
into this with the wrong 'struct device' as the sh_eth one he had fixed.

I would then say that as long as it goes for the NULL case, we should be
fine now.

Thanks
   j

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  reply	other threads:[~2018-04-18 13:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-17 13:35 Jacopo Mondi
2018-04-17 13:54 ` Thomas Petazzoni
2018-04-17 13:59   ` jacopo mondi
2018-04-20  8:30   ` Christoph Hellwig
2018-04-17 14:04 ` Geert Uytterhoeven
2018-04-17 14:20   ` jacopo mondi
2018-04-18  9:13 ` Sergei Shtylyov
2018-04-18 10:47 ` Christoph Hellwig
2018-04-18 13:13   ` jacopo mondi [this message]
2018-04-20  8:31     ` Christoph Hellwig
2018-04-20  9:59       ` Geert Uytterhoeven
2018-04-20 14:56         ` Rich Felker
2018-05-02  7:41         ` jacopo mondi

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