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SubjectRe: [PATCH] SCSI: buslogic: Added check for DMA mapping errors (was Re:[BusLogic] DMA-API: device driver failed to check map error)
On 09/13/2013 09:42 AM, Tetsuo Handa wrote:
> Khalid Aziz wrote:
>> Added check for DMA mapping errors for request sense data
>> buffer. Checking for mapping error can avoid potential wild
>> writes. This patch was prompted by the warning from
>> dma_unmap when kernel is compiled with CONFIG_DMA_API_DEBUG.
>
> This patch fixes CONFIG_DMA_API_DEBUG warning.
> But excuse me, is this error path correct?
>
>> @@ -309,16 +309,17 @@ static struct blogic_ccb *blogic_alloc_ccb(struct blogic_adapter *adapter)
>> blogic_dealloc_ccb deallocates a CCB, returning it to the Host Adapter's
>> free list. The Host Adapter's Lock should already have been acquired by the
>> caller.
>> */
>>
>> -static void blogic_dealloc_ccb(struct blogic_ccb *ccb)
>> +static void blogic_dealloc_ccb(struct blogic_ccb *ccb, int dma_unmap)
>> {
>> struct blogic_adapter *adapter = ccb->adapter;
>>
>> scsi_dma_unmap(ccb->command);
>
> blogic_dealloc_ccb() uses "ccb->command". But
>
>> - pci_unmap_single(adapter->pci_device, ccb->sensedata,
>> + if (dma_unmap)
>> + pci_unmap_single(adapter->pci_device, ccb->sensedata,
>> ccb->sense_datalen, PCI_DMA_FROMDEVICE);
>>
>> ccb->command = NULL;
>> ccb->status = BLOGIC_CCB_FREE;
>> ccb->next = adapter->free_ccbs;
>> @@ -3177,13 +3179,21 @@ static int blogic_qcmd_lck(struct scsi_cmnd *command,
>> ccb->legacy_tag = queuetag;
>> }
>> }
>> memcpy(ccb->cdb, cdb, cdblen);
>> ccb->sense_datalen = SCSI_SENSE_BUFFERSIZE;
>> - ccb->sensedata = pci_map_single(adapter->pci_device,
>> + sense_buf = pci_map_single(adapter->pci_device,
>> command->sense_buffer, ccb->sense_datalen,
>> PCI_DMA_FROMDEVICE);
>> + if (dma_mapping_error(&adapter->pci_device->dev, sense_buf)) {
>> + blogic_err("DMA mapping for sense data buffer failed\n",
>> + adapter);
>> + scsi_dma_map(command);
>> + blogic_dealloc_ccb(ccb, 0);
>
> when was "ccb->command = command;" called before calling blogic_dealloc_ccb()?
>
>> + return SCSI_MLQUEUE_HOST_BUSY;
>> + }
>> + ccb->sensedata = sense_buf;
>> ccb->command = command;
>> command->scsi_done = comp_cb;
>> if (blogic_multimaster_type(adapter)) {
>> /*
>> Place the CCB in an Outgoing Mailbox. The higher levels
>
> Also, what happens if "scsi_dma_map(command);" returned -ENOMEM ?
> If you are calling scsi_dma_map() because blogic_dealloc_ccb() calls
> scsi_dma_unmap(), why can't we do like
>
> {
> struct blogic_adapter *adapter = ccb->adapter;
> ccb->command = NULL;
> ccb->status = BLOGIC_CCB_FREE;
> ccb->next = adapter->free_ccbs;
> adapter->free_ccbs = ccb;
> }
>
> instead of
>
> scsi_dma_map(command);
> blogic_dealloc_ccb(ccb);
>
> ?
>

That is a typo. I was going to call just scsi_dma_unmap(), had copied
down the previous down the previous scsi_dma_map() line, read the code
further and decided I needed to call blogic_dealloc_ccb() instead so we
don't leak CCBs, added the call to blogic_dealloc_ccb() and forgot to
delete the previously added and unfinished line. scsi_dma_map() had
already been called earlier which is why scsi_dma_unmap() needs to be
called which is taken care of by blogic_dealloc_ccb().

I need to delete the call to scsi_dma_map() which was not supposed to be
there and move "ccb->command = command;" up before the call to
dma_mapping_error(). I will send out an updated patch.

Good catch. Thanks!

--
Khalid


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