Vulnerability: drivers/media/v4l2-core/videobuf2-v4l2.c in the Linux kernel before 4.5.3 allows local users to cause a denial of service (kernel memory write operation) or possibly have unspecified other impact via a crafted number of planes in a VIDIOC_DQBUF ioctl call.
Vulnerability ID: CVE-2016-4568
CWE: CWE-119
Severity score: 10
Project: https://github.com/torvalds/linux
Published: 2016-05-23
File: drivers/media/v4l2-core/videobuf2-v4l2.c
Commit message: [media] videobuf2-v4l2: Verify planes array in buffer dequeueing

When a buffer is being dequeued using VIDIOC_DQBUF IOCTL, the exact buffer
which will be dequeued is not known until the buffer has been removed from
the queue. The number of planes is specific to a buffer, not to the queue.

This does lead to the situation where multi-plane buffers may be requested
and queued with n planes, but VIDIOC_DQBUF IOCTL may be passed an argument
struct with fewer planes.

__fill_v4l2_buffer() however uses the number of planes from the dequeued
videobuf2 buffer, overwriting kernel memory (the m.planes array allocated
in video_usercopy() in v4l2-ioctl.c)  if the user provided fewer
planes than the dequeued buffer had. Oops!

Fixes: b0e0e1f83de3 ("[media] media: videobuf2: Prepare to divide videobuf2")

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: stable@vger.kernel.org # for v4.4 and later
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Commit author: Sakari Ailus

Vulnerable version (before fix):
 static int __verify_planes_array(struct vb2_buffer *vb, const struct v4l2_buffer 	return 0; }  /**  * __verify_length() - Verify that the bytesused value for each plane fits in  * the plane length and that the data offset doesn't exceed the bytesused value. static int __fill_vb2_buffer(struct vb2_buffer *vb, }  static const struct vb2_buf_ops v4l2_buf_ops = { 	.fill_user_buffer	= __fill_v4l2_buffer, 	.fill_vb2_buffer	= __fill_vb2_buffer, 	.copy_timestamp		= __copy_timestamp,

Fixed version (after fix):
 static int __verify_planes_array(struct vb2_buffer *vb, const struct v4l2_buffer 	return 0; }  static int __verify_planes_array_core(struct vb2_buffer *vb, const void *pb) { 	return __verify_planes_array(vb, pb); }  /**  * __verify_length() - Verify that the bytesused value for each plane fits in  * the plane length and that the data offset doesn't exceed the bytesused value. static int __fill_vb2_buffer(struct vb2_buffer *vb, }  static const struct vb2_buf_ops v4l2_buf_ops = { 	.verify_planes_array	= __verify_planes_array_core, 	.fill_user_buffer	= __fill_v4l2_buffer, 	.fill_vb2_buffer	= __fill_vb2_buffer, 	.copy_timestamp		= __copy_timestamp,

Patch:
patch: @@ -74,6 +74,11 @@ static int __verify_planes_array(struct vb2_buffer *vb, const struct v4l2_buffer
 	return 0;
 }
 
+static int __verify_planes_array_core(struct vb2_buffer *vb, const void *pb)
+{
+	return __verify_planes_array(vb, pb);
+}
+
 /**
  * __verify_length() - Verify that the bytesused value for each plane fits in
  * the plane length and that the data offset doesn't exceed the bytesused value.
@@ -437,6 +442,7 @@ static int __fill_vb2_buffer(struct vb2_buffer *vb,
 }
 
 static const struct vb2_buf_ops v4l2_buf_ops = {
+	.verify_planes_array	= __verify_planes_array_core,
 	.fill_user_buffer	= __fill_v4l2_buffer,
 	.fill_vb2_buffer	= __fill_vb2_buffer,
 	.copy_timestamp		= __copy_timestamp,
path: drivers/media/v4l2-core/videobuf2-v4l2.c