Re: Bugs in scsi_vpd_inquiry()

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Tue, 2009-08-11 at 10:53 -0400, Alan Stern wrote:
> On Tue, 11 Aug 2009, Boaz Harrosh wrote:
> 
> > This is certainly a bug. Otherwise I would get all my pages 4 bytes short
> > and wonder why.
> > 
> > I wish the bug would explain that stupid USB device Martin was fixing.
> > "I die if evpd page=0 is read" is a very brain dead thing. But there
> > is no overflow in current code, only underflow.
> > 
> > If you are at it could you please fix all the bugs in this code: ;-)
> 
> The USB problem shouldn't affect anything thanks to Martin's other
> changes (sd won't read VPD for devices with scsi_level <= SCSI_2).  So
> how does this revised patch look?
> 
> 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
> @@ -969,7 +969,7 @@ EXPORT_SYMBOL(scsi_track_queue_full);
>   * @sdev: The device to ask
>   * @buffer: Where to put the result
>   * @page: Which Vital Product Data to return
> - * @len: The length of the buffer
> + * @len: The length of the data (= buffer length - 4)

Really, no.  The former is the correct (and universally used
definition).  This one you propose is asking for confusion and misuse.

>   *
>   * This is an internal helper function.  You probably want to use
>   * scsi_get_vpd_page instead.
> @@ -980,7 +980,10 @@ static int scsi_vpd_inquiry(struct scsi_
>  							u8 page, unsigned len)
>  {
>  	int result;
> -	unsigned char cmd[16];
> +	int resid;
> +	unsigned char cmd[6];
> +
> +	len += 4;		/* Include room for the header bytes */
>  
>  	cmd[0] = INQUIRY;
>  	cmd[1] = 1;		/* EVPD */
> @@ -989,17 +992,19 @@ static int scsi_vpd_inquiry(struct scsi_
>  	cmd[4] = len & 0xff;
>  	cmd[5] = 0;		/* Control byte */
>  
> +	buffer[1] = ~page;

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.

James