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SubjectRe: 2.5.40-ac4 kernel BUG at slab.c:1477!

Only that if it is SG it must conform the ATA/ATAPI DMA on 64kb on 4b
boundaries. Some what basic stuff iirc, but remember this is piped via
scsi and the eh-stratagy/joke leaves something to be desired.

One concern could be crossing SG lists with the device in PIO, that could
get hairy.

On Sun, 6 Oct 2002, Manfred Spraul wrote:

> > This happens at random during boot when loading modules.
> > About half of the time ide-scsi works fine.
> > The system continues to boot after the BUG with /dev/hdc unaccessible.
>
> from mm/slab.c:
>
> 1475 if (xchg((unsigned long *)objp, RED_MAGIC1) != RED_MAGIC2)
> 1476 /* Either write before start, or a double free. */
> 1477 BUG();
>
> You run an uniprocessor kernel, with slab debugging enabled, and the
> red-zoning test notices a write before the beginning of the buffer
> during scsi_probe_and_add_lun, with ide-scsi.
>
> Andre: Do you know if ide-scsi makes any assumptions about memory
> alignment of the input buffers? With slab debugging disabled, the
> alignment is 32 or 64 bytes, with debugging enabled, it's just 4 byte
> [actually sizeof(void*)] aligned.
>
> Murray, could you apply the attached patch? It dumps the redzone value
> during scsi_probe_and_add_lun. Hopefully this will help to find who
> corrupts the buffers.
>
> --
> Manfred
>

Andre Hedrick
LAD Storage Consulting Group

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