linux-kernel - Re: [PATCH] return hidden bug

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Message-ID: <2c0942db0710220942he5e9199i2e327df3c5676a6a@mail.gmail.com>
Date:	Mon, 22 Oct 2007 09:42:28 -0700
From:	"Ray Lee" <ray-lk@...rabbit.org>
To:	"Rik van Riel" <riel@...hat.com>
Cc:	"Roel Kluin" <12o3l@...cali.nl>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] return hidden bug

On 10/21/07, Rik van Riel <riel@...hat.com> wrote:
> On Mon, 22 Oct 2007 03:05:05 +0200
> Roel Kluin <12o3l@...cali.nl> wrote:
>
> >     return hidden bug
> >
> >     Signed-off-by: Roel Kluin <12o3l@...cali.nl>
> >
> > diff --git a/arch/alpha/kernel/pci_iommu.c
> > b/arch/alpha/kernel/pci_iommu.c index e1c4707..6a69425 100644
> > --- a/arch/alpha/kernel/pci_iommu.c
> > +++ b/arch/alpha/kernel/pci_iommu.c
> > @@ -365,8 +365,8 @@ pci_unmap_single(struct pci_dev *pdev, dma_addr_t
> > dma_addr, size_t size, printk(KERN_ERR "Bogus pci_unmap_single:
> > dma_addr %lx " " base %lx size %x\n", dma_addr, arena->dma_base,
> >                      arena->size);
> > -             return;
> >               BUG();
> > +             return;
> >       }
> >
> >       npages = calc_npages((dma_addr & ~PAGE_MASK) + size);
>
> BUG() will terminate the process that runs into it, so you can
> just remove the return alltogether.  If BUG() is hit, the return
> will never be reached.

I'm sorry, perhaps I poured myself a cup of stupid this morning, but
isn't the above patch effectively introducing a BUG where none could
be reached before? In other words, for the patch to have zero
behavioral change, wouldn't it have to remove the BUG() altogether?

Ray
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