linux-kernel - [PATCH 3.19.y-ckt 91/92] vhost/scsi: potential memory corruption

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Message-Id: <1432654896-28478-92-git-send-email-kamal@canonical.com>
Date:	Tue, 26 May 2015 08:41:35 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	Nicholas Bellinger <nab@...ux-iscsi.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 91/92] vhost/scsi: potential memory corruption

3.19.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

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

From: Dan Carpenter <dan.carpenter@...cle.com>

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@...cle.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
Reference: CVE-2015-4036
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/vhost/scsi.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index d695b16..be0517f 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1253,7 +1253,7 @@ 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;
@@ -2124,12 +2124,12 @@ 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);
-- 
1.9.1

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