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From: Rich Felker <dalias@libc.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	jacopo mondi <jacopo@jmondi.org>,
	Jacopo Mondi <jacopo+renesas@jmondi.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Linux-sh list <linux-sh@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sh: mm: Fix unprotected access to struct device
Date: Fri, 20 Apr 2018 14:56:21 +0000	[thread overview]
Message-ID: <20180420145621.GQ3094@brightrain.aerifal.cx> (raw)
In-Reply-To: <CAMuHMdWwJrUgOjaAX1oUHd+KFUMuUzcH6g29zC2mJX377oAHiA@mail.gmail.com>

On Fri, Apr 20, 2018 at 11:59:13AM +0200, Geert Uytterhoeven wrote:
> Hi Christoph,
> 
> On Fri, Apr 20, 2018 at 10:31 AM, Christoph Hellwig <hch@infradead.org> wrote:
> > On Wed, Apr 18, 2018 at 03:13:14PM +0200, jacopo mondi wrote:
> >> 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.
> >
> > Great!
> >
> >> 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.
> >
> > Yes, we'll need fixes there.  Other DMA ops implementations also look
> > at struct device, so they generally are buggy.
> >
> >> I would then say that as long as it goes for the NULL case, we should be
> >> fine now.
> >
> > Then I'd say skil that part, please.
> 
> The major reason for keeping the NULL WARN_ON() checks is to make it
> obvious to the developer what is wrong, and fall back to the old behavior.
> 
> Without the checks, the kernel will just crash during early startup,
> without a clue in the (missing) kernel output, usually leading to a
> frustrating bisection experience (if the developer is sufficiently motivated,
> at all).
> 
> Hence my vote for keeping the checks.

Sounds good to me.

Rich

WARNING: multiple messages have this Message-ID (diff)
From: Rich Felker <dalias@libc.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Christoph Hellwig <hch@infradead.org>,
	jacopo mondi <jacopo@jmondi.org>,
	Jacopo Mondi <jacopo+renesas@jmondi.org>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Linux-sh list <linux-sh@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] sh: mm: Fix unprotected access to struct device
Date: Fri, 20 Apr 2018 10:56:21 -0400	[thread overview]
Message-ID: <20180420145621.GQ3094@brightrain.aerifal.cx> (raw)
In-Reply-To: <CAMuHMdWwJrUgOjaAX1oUHd+KFUMuUzcH6g29zC2mJX377oAHiA@mail.gmail.com>

On Fri, Apr 20, 2018 at 11:59:13AM +0200, Geert Uytterhoeven wrote:
> Hi Christoph,
> 
> On Fri, Apr 20, 2018 at 10:31 AM, Christoph Hellwig <hch@infradead.org> wrote:
> > On Wed, Apr 18, 2018 at 03:13:14PM +0200, jacopo mondi wrote:
> >> 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.
> >
> > Great!
> >
> >> 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.
> >
> > Yes, we'll need fixes there.  Other DMA ops implementations also look
> > at struct device, so they generally are buggy.
> >
> >> I would then say that as long as it goes for the NULL case, we should be
> >> fine now.
> >
> > Then I'd say skil that part, please.
> 
> The major reason for keeping the NULL WARN_ON() checks is to make it
> obvious to the developer what is wrong, and fall back to the old behavior.
> 
> Without the checks, the kernel will just crash during early startup,
> without a clue in the (missing) kernel output, usually leading to a
> frustrating bisection experience (if the developer is sufficiently motivated,
> at all).
> 
> Hence my vote for keeping the checks.

Sounds good to me.

Rich

  reply	other threads:[~2018-04-20 14:56 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-17 13:35 [PATCH] sh: mm: Fix unprotected access to struct device Jacopo Mondi
2018-04-17 13:35 ` Jacopo Mondi
2018-04-17 13:54 ` Thomas Petazzoni
2018-04-17 13:54   ` Thomas Petazzoni
2018-04-17 13:59   ` jacopo mondi
2018-04-17 13:59     ` jacopo mondi
2018-04-20  8:30   ` Christoph Hellwig
2018-04-20  8:30     ` Christoph Hellwig
2018-04-17 14:04 ` Geert Uytterhoeven
2018-04-17 14:04   ` Geert Uytterhoeven
2018-04-17 14:20   ` jacopo mondi
2018-04-17 14:20     ` jacopo mondi
2018-04-18  9:13 ` Sergei Shtylyov
2018-04-18  9:13   ` Sergei Shtylyov
2018-04-18 10:47 ` Christoph Hellwig
2018-04-18 10:47   ` Christoph Hellwig
2018-04-18 13:13   ` jacopo mondi
2018-04-18 13:13     ` jacopo mondi
2018-04-20  8:31     ` Christoph Hellwig
2018-04-20  8:31       ` Christoph Hellwig
2018-04-20  9:59       ` Geert Uytterhoeven
2018-04-20  9:59         ` Geert Uytterhoeven
2018-04-20 14:56         ` Rich Felker [this message]
2018-04-20 14:56           ` Rich Felker
2018-05-02  7:41         ` jacopo mondi
2018-05-02  7:41           ` jacopo mondi

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