libata: array underflow in ata_find_dev()
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.carpenter@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # all versions at this point
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index d462c5a..44ba292 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -3030,10 +3030,12 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
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];
}