Re: [Qemu-devel] [PATCH] workaround for cmd646 bmdma register access while no dma is active

[Igor Kovalenko <igor.v.kovalenko@gmail.com>]

On Sun, Dec 13, 2009 at 6:50 PM, Blue Swirl <blauwirbel@gmail.com> wrote:
> On Sun, Dec 13, 2009 at 12:23 PM, Igor V. Kovalenko
> <igor.v.kovalenko@gmail.com> wrote:
>> From: Igor V. Kovalenko <igor.v.kovalenko@gmail.com>
>>
>> This is a workaround only, and is a partial revert
>> of a few changes to BMDMAState which removed pci_dev
>> field on the way.
>>
>> - cmd646 pci_from_bm() expects bm->unit value to
>> correspond with bm data being passed to callback
>> as opaque pointer. This breaks when write to dma
>> control register of second channel happens when no
>> dma operation is in progress, so bm->unit is zero
>> for second channel, and pci_from_bm() returns garbage
>> pointer. Crash happens shortly after that while
>> dereferencing that pointer.
>
>>  static PCIIDEState *pci_from_bm(BMDMAState *bm)
>>  {
>> +    return bm->pci_dev;
>>     if (bm->unit == 0) {
>>         return container_of(bm, PCIIDEState, bmdma[0]);
>>     } else {
>
> I think you should delete the rest of the function, unused code is
> useless and if someone decides to fix and restore the old code, they
> can fetch it from git.

Thanks, resent with this change.

-- 
Kind regards,
Igor V. Kovalenko