From: Ashutosh Dixit <ashutosh.dixit@intel.com>
Date: Wed, 27 Apr 2016 21:36:05 +0000 (-0700)
Subject: misc: mic: Fix for double fetch security bug in VOP driver
X-Git-Tag: v3.16.37~18
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=72aaf646fb6b6f8f7befb44cbd5b1acd3bb5b483;p=thirdparty%2Fkernel%2Fstable.git

misc: mic: Fix for double fetch security bug in VOP driver

commit 9bf292bfca94694a721449e3fd752493856710f6 upstream.

The MIC VOP driver does two successive reads from user space to read a
variable length data structure. Kernel memory corruption can result if
the data structure changes between the two reads. This patch disallows
the chance of this happening.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=116651
Reported by: Pengfei Wang <wpengfeinudt@gmail.com>
Reviewed-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16:
 - Adjust filename, context
 - goto exit on failure]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/drivers/misc/mic/host/mic_virtio.c b/drivers/misc/mic/host/mic_virtio.c
index 7e1ef0ebbb800..dba3c19929db0 100644
--- a/drivers/misc/mic/host/mic_virtio.c
+++ b/drivers/misc/mic/host/mic_virtio.c
@@ -456,6 +456,11 @@ static int mic_copy_dp_entry(struct mic_vdev *mvdev,
 			__func__, __LINE__, ret);
 		goto exit;
 	}
+	/* Ensure desc has not changed between the two reads */
+	if (memcmp(&dd, dd_config, sizeof(dd))) {
+		ret = -EINVAL;
+		goto exit;
+	}
 
 	vqconfig = mic_vq_config(dd_config);
 	for (i = 0; i < dd.num_vq; i++) {