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: v4.6.1~19
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2a9369456a384d84c521c8ebb48d247e8738f84f;p=linux

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>
---

diff --git a/drivers/misc/mic/vop/vop_vringh.c b/drivers/misc/mic/vop/vop_vringh.c
index 88e45234d527..af57d2caac75 100644
--- a/drivers/misc/mic/vop/vop_vringh.c
+++ b/drivers/misc/mic/vop/vop_vringh.c
@@ -950,6 +950,11 @@ static long vop_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 			ret = -EINVAL;
 			goto free_ret;
 		}
+		/* Ensure desc has not changed between the two reads */
+		if (memcmp(&dd, dd_config, sizeof(dd))) {
+			ret = -EINVAL;
+			goto free_ret;
+		}
 		mutex_lock(&vdev->vdev_mutex);
 		mutex_lock(&vi->vop_mutex);
 		ret = vop_virtio_add_device(vdev, dd_config);