vhost/scsi: potential memory corruption

commit 59c816c1f24df0204e01851431d3bab3eb76719c upstream.

This code in vhost_scsi_make_tpg() is confusing because we limit "tpgt"
to UINT_MAX but the data type of "tpg->tport_tpgt" and that is a u16.

I looked at the context and it turns out that in
vhost_scsi_set_endpoint(), "tpg->tport_tpgt" is used as an offset into
the vs_tpg[] array which has VHOST_SCSI_MAX_TARGET (256) elements so
anything higher than 255 then it is invalid.  I have made that the limit
now.

In vhost_scsi_send_evt() we mask away values higher than 255, but now
that the limit has changed, we don't need the mask.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
[ luis: backported to 3.16: functions rename:
  - tcm_vhost_send_evt -> vhost_scsi_send_evt
  - tcm_vhost_make_tpg -> vhost_scsi_make_tpg ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index befe07b1e71d512b6713a33672389475faa4b168..0dfb3fd6e8361db3ece1d1825bb6992c3bb5c26e 100644 (file)
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1251,7 +1251,7 @@ tcm_vhost_send_evt(struct vhost_scsi *vs,
                 * lun[4-7] need to be zero according to virtio-scsi spec.
                 */
                evt->event.lun[0] = 0x01;
-               evt->event.lun[1] = tpg->tport_tpgt & 0xFF;
+               evt->event.lun[1] = tpg->tport_tpgt;
                if (lun->unpacked_lun >= 256)
                        evt->event.lun[2] = lun->unpacked_lun >> 8 | 0x40 ;
                evt->event.lun[3] = lun->unpacked_lun & 0xFF;
@@ -2122,12 +2122,12 @@ tcm_vhost_make_tpg(struct se_wwn *wwn,
                        struct tcm_vhost_tport, tport_wwn);
 
        struct tcm_vhost_tpg *tpg;
-       unsigned long tpgt;
+       u16 tpgt;
        int ret;
 
        if (strstr(name, "tpgt_") != name)
                return ERR_PTR(-EINVAL);
-       if (kstrtoul(name + 5, 10, &tpgt) || tpgt > UINT_MAX)
+       if (kstrtou16(name + 5, 10, &tpgt) || tpgt >= VHOST_SCSI_MAX_TARGET)
                return ERR_PTR(-EINVAL);
 
        tpg = kzalloc(sizeof(struct tcm_vhost_tpg), GFP_KERNEL);