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 88e45234d527518e0d449d598c5f04a5be5538a1..af57d2caac750a8cdf4b1d3e739bdf37d977ebf3 100644 (file)
--- 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);