linux-kernel - Re: BUG: NULL pointer dereference at 00000000 -- IP: [<f8e783d5>] :b43:b43_dma_mapping

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Date:	Tue, 10 Jun 2008 10:42:38 -0400
From:	"Miles Lane" <miles.lane@...il.com>
To:	"Michael Buesch" <mb@...sch.de>
Cc:	"Vegard Nossum" <vegard.nossum@...il.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>
Subject: Re: BUG: NULL pointer dereference at 00000000 -- IP: [<f8e783d5>] :b43:b43_dma_mapping_error+0x16/0x155

Sorry, I forgot to label the kernel tree.  It is 2.6.26-rc5-mm2.

On Tue, Jun 10, 2008 at 10:37 AM, Michael Buesch <mb@...sch.de> wrote:
> On Tuesday 10 June 2008 16:34:21 Michael Buesch wrote:
>> On Tuesday 10 June 2008 16:29:17 Vegard Nossum wrote:
>> > On Tue, Jun 10, 2008 at 4:23 PM, Michael Buesch <mb@...sch.de> wrote:
>> > > On Tuesday 10 June 2008 16:09:37 Miles Lane wrote:
>> > >> BUG: unable to handle kernel NULL pointer dereference at 00000000
>> > >> IP: [<f8e783d5>] :b43:b43_dma_mapping_error+0x16/0x155
>> > >
>> > >
>> > > It seems to crash at
>> > >  60 extern const struct dma_mapping_ops *dma_ops;
>> > >  61
>> > >  62 static inline int dma_mapping_error(dma_addr_t dma_addr)
>> > >  63 {
>> > >  64         if (dma_ops->mapping_error)
>> > >  65                 return dma_ops->mapping_error(dma_addr);
>> > >  66
>> > >  67         return (dma_addr == bad_dma_address);
>> > >  68 }
>> >
>> > No, this is wrong.
>> >
>> > /* Check if a DMA mapping address is invalid. */
>> > static bool b43_dma_mapping_error(struct b43_dmaring *ring,
>> >                                   dma_addr_t addr,
>> >                                   size_t buffersize, bool dma_to_device)
>> > {
>> >         if (unlikely(dma_mapping_error(ring->dev->dev->dma_dev, addr)))
>> >
>> > It crashes on this line ---^
>>
>> Which calls dma_mapping_error(), correct?
>>
>> But you are right. I see the bug now.
>> ring->dev is assigned after the call.
>> I wonder why it works reliably on all of my machines.
>>
>
> Ehm no wait a second...
> What strange tree are you looking at?
> This is a copy of the code from my local tree.
>
>  516 /* Check if a DMA mapping address is invalid. */
>  517 static bool b43_dma_mapping_error(struct b43_dmaring *ring,
>  518                                   dma_addr_t addr,
>  519                                   size_t buffersize, bool dma_to_device)
>  520 {
>  521         if (unlikely(dma_mapping_error(addr)))
>  522                 return 1;
>
> This code is perfectly fine.
> This must be some merge error in some upstream tree.
>
> --
> Greetings Michael.
>
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