drm/atmel-hlcdc: fix use-after-free of drm_crtc_commit after release

In the Linux kernel, the following vulnerability has been resolved:

drm/atmel-hlcdc: fix use-after-free of drm_crtc_commit after release

The atmel_hlcdc_plane_atomic_duplicate_state() callback was copying

the atmel_hlcdc_plane state structure without properly duplicating the

drm_plane_state. In particular, state->commit remained set to the old

state commit, which can lead to a use-after-free in the next

drm_atomic_commit() call.

Fix this by calling

__drm_atomic_helper_duplicate_plane_state(), which correctly clones

the base drm_plane_state (including the ->commit pointer).

It has been seen when closing and re-opening the device node while

another DRM client (e.g. fbdev) is still attached:

=============================================================================

BUG kmalloc-64 (Not tainted): Poison overwritten

-----------------------------------------------------------------------------

0xc611b344-0xc611b344 @offset=836. First byte 0x6a instead of 0x6b

FIX kmalloc-64: Restoring Poison 0xc611b344-0xc611b344=0x6b

Allocated in drm_atomic_helper_setup_commit+0x1e8/0x7bc age=178 cpu=0

pid=29

drm_atomic_helper_setup_commit+0x1e8/0x7bc

drm_atomic_helper_commit+0x3c/0x15c

drm_atomic_commit+0xc0/0xf4

drm_framebuffer_remove+0x4cc/0x5a8

drm_mode_rmfb_work_fn+0x6c/0x80

process_one_work+0x12c/0x2cc

worker_thread+0x2a8/0x400

kthread+0xc0/0xdc

ret_from_fork+0x14/0x28

Freed in drm_atomic_helper_commit_hw_done+0x100/0x150 age=8 cpu=0

pid=169

drm_atomic_helper_commit_hw_done+0x100/0x150

drm_atomic_helper_commit_tail+0x64/0x8c

commit_tail+0x168/0x18c

drm_atomic_helper_commit+0x138/0x15c

drm_atomic_commit+0xc0/0xf4

drm_atomic_helper_set_config+0x84/0xb8

drm_mode_setcrtc+0x32c/0x810

drm_ioctl+0x20c/0x488

sys_ioctl+0x14c/0xc20

ret_fast_syscall+0x0/0x54

Slab 0xef8bc360 objects=21 used=16 fp=0xc611b7c0

flags=0x200(workingset|zone=0)

Object 0xc611b340 @offset=832 fp=0xc611b7c0