CVE-2015-4036 (published 2015-08-31T20:59Z)

Array index error in the tcm_vhost_make_tpg function in drivers/vhost/scsi.c in the Linux kernel before 4.0 might allow guest OS users to cause a denial of service (memory corruption) or possibly have unspecified other impact via a crafted VHOST_SCSI_SET_ENDPOINT ioctl call.  NOTE: the affected function was renamed to vhost_scsi_make_tpg before the vulnerability was announced.

Severity: HIGH
CVSS v2 base score: 7.2 (AV:L/AC:L/Au:N/C:C/I:C/A:C)

Weakness information:
cwe_id: CWE-119
cwe_name: Improper Restriction of Operations within the Bounds of a Memory Buffer
description: The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
extended_description: 
            Certain languages allow direct addressing of memory locations and do not automatically ensure that these locations are valid for the memory buffer that is being referenced. This can cause read or write operations to be performed on memory locations that may be associated with other variables, data structures, or internal program data.
         
         

Fix information:
repo_url: https://github.com/torvalds/linux
commit_details: repo_url: https://github.com/torvalds/linux
author: Dan Carpenter
author_date: 2015-02-05 10:37:33+03:00
msg: 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 <dan.carpenter@oracle.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
repository: repo_url: https://github.com/torvalds/linux
repo_name: torvalds/linux
description: Linux kernel source tree
repo_language: C
owner: torvalds
file_changes: filename: scsi.c
change_type: ModificationType.MODIFY
diff: @@ -1249,7 +1249,7 @@ 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;
@@ -2120,12 +2120,12 @@ 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);

programming_language: C