Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Jinbum Park <jinb.park7@gmail.com>, Jens Axboe <axboe@kernel.dk>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.14 55/89] pktcdvd: Fix possible Spectre-v1 for
 pkt_devs
Thread-Topic: [PATCH AUTOSEL 4.14 55/89] pktcdvd: Fix possible Spectre-v1 for
 pkt_devs
Thread-Index: AQHUQr3gxWl9CLEDWE+4Ki9jA4+GXA==
Date:   Sun, 2 Sep 2018 13:07:17 +0000
Message-ID: <20180902064918.183387-55-alexander.levin@microsoft.com>
References: <20180902064918.183387-1-alexander.levin@microsoft.com>
In-Reply-To: <20180902064918.183387-1-alexander.levin@microsoft.com>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: microsoft.com does not designate
 permitted sender hosts)
spamdiagnosticoutput: 1:99
spamdiagnosticmetadata: NSPM
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 10b23134-2385-4459-c0de-08d610d513d7
X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Sep 2018 13:07:17.6257
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR21MB0503
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

From: Jinbum Park <jinb.park7@gmail.com>

[ Upstream commit 55690c07b44a82cc3359ce0c233f4ba7d80ba145 ]

User controls @dev_minor which to be used as index of pkt_devs.
So, It can be exploited via Spectre-like attack. (speculative execution)

This kind of attack leaks address of pkt_devs, [1]
It leads an attacker to bypass security mechanism such as KASLR.

So sanitize @dev_minor before using it to prevent attack.

[1] https://github.com/jinb-park/linux-exploit/
tree/master/exploit-remaining-spectre-gadget/leak_pkt_devs.c

Signed-off-by: Jinbum Park <jinb.park7@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/block/pktcdvd.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index 531a0915066b..11ec92e47455 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -67,7 +67,7 @@
 #include <scsi/scsi.h>
 #include <linux/debugfs.h>
 #include <linux/device.h>
-
+#include <linux/nospec.h>
 #include <linux/uaccess.h>
=20
 #define DRIVER_NAME	"pktcdvd"
@@ -2231,6 +2231,8 @@ static struct pktcdvd_device *pkt_find_dev_from_minor=
(unsigned int dev_minor)
 {
 	if (dev_minor >=3D MAX_WRITERS)
 		return NULL;
+
+	dev_minor =3D array_index_nospec(dev_minor, MAX_WRITERS);
 	return pkt_devs[dev_minor];
 }
=20
--=20
2.17.1