Re: Bugs in scsi_vpd_inquiry()

Alan Stern
2009-08-11T15:38:03Z

On Tue, 11 Aug 2009, James Bottomley wrote:

> > > This is pointless and dangerous: Some architectures will invalidate
> > > caches for DMA not flush them, so it might not do what you think it
> > > does.
> > >
> >
> > Then you can't do that "after check" either. It's a simple minefield.
> > What do you suggest?
>
> Well, nothing really, like the original code. Byzantine checking is
> never a good idea. You always assume that if a device told you it did
> what you told it, it actually did. If we find devices that fail this
> simple premise, then we get into blacklists and other forms of
> nastiness.

Okay, then how about this?

Alan Stern

Index: usb-2.6/drivers/scsi/scsi.c
===================================================================
--- usb-2.6.orig/drivers/scsi/scsi.c
+++ usb-2.6/drivers/scsi/scsi.c
@@ -980,7 +980,8 @@ static int scsi_vpd_inquiry(struct scsi_
u8 page, unsigned len)
{
int result;
- unsigned char cmd[16];
+ int resid;
+ unsigned char cmd[6];

cmd[0] = INQUIRY;
cmd[1] = 1; /* EVPD */
@@ -994,12 +995,12 @@ static int scsi_vpd_inquiry(struct scsi_
* all the existing users tried this hard.
*/
result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer,
- len + 4, NULL, 30 * HZ, 3, NULL);
+ len, NULL, 30 * HZ, 3, &resid);
if (result)
return result;

- /* Sanity check that we got the page back that we asked for */
- if (buffer[1] != page)
+ /* Sanity check that we at least got the header */
+ if (resid > len - 4)
return -EIO;

return 0;
@@ -1027,7 +1028,7 @@ unsigned char *scsi_get_vpd_page(struct
return NULL;

/* Ask for all the pages supported by this device */
- result = scsi_vpd_inquiry(sdev, buf, 0, 255);
+ result = scsi_vpd_inquiry(sdev, buf, 0, 255 + 4);
if (result)
goto fail;

@@ -1042,7 +1043,7 @@ unsigned char *scsi_get_vpd_page(struct
goto fail;

found:
- result = scsi_vpd_inquiry(sdev, buf, page, 255);
+ result = scsi_vpd_inquiry(sdev, buf, page, 255 + 4);
if (result)
goto fail;

@@ -1056,7 +1057,7 @@ unsigned char *scsi_get_vpd_page(struct

kfree(buf);
buf = kmalloc(len + 4, GFP_KERNEL);
- result = scsi_vpd_inquiry(sdev, buf, page, len);
+ result = scsi_vpd_inquiry(sdev, buf, page, len + 4);
if (result)
goto fail;