Re: [patch] [SCSI] scsi_transport_sas: check for allocation failure

[Douglas Gilbert]

On 13-03-08 05:50 PM, James Bottomley wrote:
> On Fri, 2013-03-08 at 12:57 -0500, Douglas Gilbert wrote:
> > On 13-03-08 07:02 AM, Dan Carpenter wrote:
> > > Static checkers complain that this allocation isn't checked.  We
> > > should return zero if the allocation fails.
> > >
> > > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > >
> > > diff --git a/drivers/scsi/scsi_transport_sas.c b/drivers/scsi/scsi_transport_sas.c
> > > index 1b68142..a022997 100644
> > > --- a/drivers/scsi/scsi_transport_sas.c
> > > +++ b/drivers/scsi/scsi_transport_sas.c
> > > @@ -379,9 +379,12 @@ sas_tlr_supported(struct scsi_device *sdev)
> > >    {
> > >    	const int vpd_len = 32;
> > >    	struct sas_end_device *rdev = sas_sdev_to_rdev(sdev);
> > > -	char *buffer = kzalloc(vpd_len, GFP_KERNEL);
> > > +	char *buffer;
> > >    	int ret = 0;
> > >
> > > +	buffer = kzalloc(vpd_len, GFP_KERNEL);
> > > +	if (!buffer)
> > > +		goto out;
> > >    	if (scsi_get_vpd_page(sdev, 0x90, buffer, vpd_len))
> > >    		goto out;
> >
> > For 32 bytes, why not use the stack?
>
> Because the buffer is a DMA target.  You can't DMA to stack because of
> padding and cacheline issues.

And I went to the definition of scsi_get_vpd_page()
to see if that was called out in the header comments.
Guess what ... and those same header comments talked
about freeing a returned pointer. It needs to be
cleaned up, IMO.

Doug Gilbert

/**
 * scsi_get_vpd_page - Get Vital Product Data from a SCSI device
 * @sdev: The device to ask
 * @page: Which Vital Product Data to return
 * @buf: where to store the VPD
 * @buf_len: number of bytes in the VPD buffer area
 *
 * SCSI devices may optionally supply Vital Product Data.  Each 'page'
 * of VPD is defined in the appropriate SCSI document (eg SPC, SBC).
 * If the device supports this VPD page, this routine returns a pointer
 * to a buffer containing the data from that page.  The caller is
 * responsible for calling kfree() on this pointer when it is no longer
 * needed.  If we cannot retrieve the VPD page this routine returns %NULL.
 */
int scsi_get_vpd_page(struct scsi_device *sdev, u8 page, unsigned char *buf,
                      int buf_len)


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