[PATCH 4.6 082/100] misc: mic: Fix for double fetch security bug in VOP driver

Greg Kroah-Hartman
2016-05-30T21:18:19Z

From: Ashutosh Dixit <ashutosh.dixit@intel.com>

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>

---
drivers/misc/mic/vop/vop_vringh.c | 5 +++++
1 file changed, 5 insertions(+)

--- 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, un
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);