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vhost/scsi: potential memory corruption

PATCH In review Dan Carpenter 2 participants 2 messages Feb 5, 2015 – Feb 6, 2015

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SCSI KVM Kernel janitors virtio core +2 more subsystems
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Dan Carpenter

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#0 lore raw

PATCH 1/1 vhost/scsi: potential memory corruption

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 <[email protected]>

---
Compile tested only.

drivers/vhost/scsi.c +3 -3
index 3e265ef..4339222 100644
@@ -1278,7 +1278,7 @@ vhost_scsi_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;

@@ -2149,12 +2149,12 @@ vhost_scsi_make_tpg(struct se_wwn *wwn,
 			struct vhost_scsi_tport, tport_wwn);
 
 	struct vhost_scsi_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 vhost_scsi_tpg), GFP_KERNEL);
#1 lore raw
Quoted 34 lines · Dan Carpenter

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 <[email protected]>

---
Compile tested only.

drivers/vhost/scsi.c +1 -2
index 3e265ef..4339222 100644
@@ -1278,7 +1278,7 @@ vhost_scsi_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;

@@ -2149,12 +2149,12 @@ vhost_scsi_make_tpg(struct se_wwn *wwn,
 			struct vhost_scsi_tport, tport_wwn);
 
 	struct vhost_scsi_tpg *tpg;
-	unsigned long tpgt;

drivers/vhost/scsi.c vhost_scsi_make_tpg(struct se_wwn *wwn, · line 2160

Quoted 10 lines
drivers/vhost/scsi.c +2 -1
+	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 vhost_scsi_tpg), GFP_KERNEL);

Nice catch Dan. Applied to target-pending/for-next.

--nab