Re: [Bug 49151] New: NULL pointer dereference in pata_acpi

[Borislav Petkov <bp@alien8.de>]

On Tue, Oct 23, 2012 at 11:05:49AM +0100, Alan Cox wrote:
> > So yes, blacklisting it and verifying that your system still operates
> > normally would be something to do. If it does, you could also build a
> > kernel with pata_acpi disabled (that is, provided you build your own
> > kernels).
> 
> The crash is still a bug. It needs chasing down.

Yes, ata_timing_find_mode gives NULL, we found that out.

Anton, Phillip, anyone willing to run this hunk below and get us the
output:

---
diff --git a/drivers/ata/pata_acpi.c b/drivers/ata/pata_acpi.c
index 09723b76beac..80d594d6e7c8 100644
--- a/drivers/ata/pata_acpi.c
+++ b/drivers/ata/pata_acpi.c
@@ -144,6 +144,13 @@ static void pacpi_set_dmamode(struct ata_port *ap, struct ata_device *adev)
 
 	/* Now stuff the nS values into the structure */
 	t = ata_timing_find_mode(adev->dma_mode);
+	if (!t) {
+		pr_err("%s: ata_timing_find_mode gives NULL; adev->dma_mode: 0x%x\n",
+		       __func__, adev->dma_mode);
+
+		return;
+	}
+
 	if (adev->dma_mode >= XFER_UDMA_0) {
 		acpi->gtm.drive[unit].dma = t->udma;
 		acpi->gtm.flags |= (1 << (2 * unit));
--

Thanks.

-- 
Regards/Gruss,
    Boris.