4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpen...@oracle.com>

commit 59a5e266c3f5c1567508888dd61a45b86daed0fa upstream.

My static checker complains that "devno" can be negative, meaning that
we read before the start of the loop.  I've looked at the code, and I
think the warning is right.  This come from /proc so it's root only or
it would be quite a quite a serious bug.  The call tree looks like this:

proc_scsi_write() <- gets id and channel from simple_strtoul()
-> scsi_add_single_device() <- calls shost->transportt->user_scan()
   -> ata_scsi_user_scan()
      -> ata_find_dev()

Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>
Signed-off-by: Tejun Heo <t...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/ata/libata-scsi.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2832,10 +2832,12 @@ static unsigned int atapi_xlat(struct at
 static struct ata_device *ata_find_dev(struct ata_port *ap, int devno)
 {
        if (!sata_pmp_attached(ap)) {
-               if (likely(devno < ata_link_max_devices(&ap->link)))
+               if (likely(devno >= 0 &&
+                          devno < ata_link_max_devices(&ap->link)))
                        return &ap->link.device[devno];
        } else {
-               if (likely(devno < ap->nr_pmp_links))
+               if (likely(devno >= 0 &&
+                          devno < ap->nr_pmp_links))
                        return &ap->pmp_link[devno].device[0];
        }
 


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