drm/amd/display: Fix slab-use-after-free in hdcp

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

drm/amd/display: Fix slab-use-after-free in hdcp

The HDCP code in amdgpu_dm_hdcp.c copies pointers to amdgpu_dm_connector
objects without incrementing the kref reference counts. When using a
USB-C dock, and the dock is unplugged, the corresponding
amdgpu_dm_connector objects are freed, creating dangling pointers in the
HDCP code. When the dock is plugged back, the dangling pointers are
dereferenced, resulting in a slab-use-after-free:

[ 66.775837] BUG: KASAN: slab-use-after-free in event_property_validate+0x42f/0x6c0 [amdgpu]
[ 66.776171] Read of size 4 at addr ffff888127804120 by task kworker/0:1/10

[ 66.776179] CPU: 0 UID: 0 PID: 10 Comm: kworker/0:1 Not tainted 6.14.0-rc7-00180-g54505f727a38-dirty #233
[ 66.776183] Hardware name: HP HP Pavilion Aero Laptop 13-be0xxx/8916, BIOS F.17 12/18/2024
[ 66.776186] Workqueue: events event_property_validate [amdgpu]
[ 66.776494] Call Trace:
[ 66.776496] <TASK>
[ 66.776497] dump_stack_lvl+0x70/0xa0
[ 66.776504] print_report+0x175/0x555
[ 66.776507] ? __virt_addr_valid+0x243/0x450
[ 66.776510] ? kasan_complete_mode_report_info+0x66/0x1c0
[ 66.776515] kasan_report+0xeb/0x1c0
[ 66.776518] ? event_property_validate+0x42f/0x6c0 [amdgpu]
[ 66.776819] ? event_property_validate+0x42f/0x6c0 [amdgpu]
[ 66.777121] __asan_report_load4_noabort+0x14/0x20
[ 66.777124] event_property_validate+0x42f/0x6c0 [amdgpu]
[ 66.777342] ? __lock_acquire+0x6b40/0x6b40
[ 66.777347] ? enable_assr+0x250/0x250 [amdgpu]
[ 66.777571] process_one_work+0x86b/0x1510
[ 66.777575] ? pwq_dec_nr_in_flight+0xcf0/0xcf0
[ 66.777578] ? assign_work+0x16b/0x280
[ 66.777580] ? lock_is_held_type+0xa3/0x130
[ 66.777583] worker_thread+0x5c0/0xfa0
[ 66.777587] ? process_one_work+0x1510/0x1510
[ 66.777588] kthread+0x3a2/0x840
[ 66.777591] ? kthread_is_per_cpu+0xd0/0xd0
[ 66.777594] ? trace_hardirqs_on+0x4f/0x60
[ 66.777597] ? _raw_spin_unlock_irq+0x27/0x60
[ 66.777599] ? calculate_sigpending+0x77/0xa0
[ 66.777602] ? kthread_is_per_cpu+0xd0/0xd0
[ 66.777605] ret_from_fork+0x40/0x90
[ 66.777607] ? kthread_is_per_cpu+0xd0/0xd0
[ 66.777609] ret_from_fork_asm+0x11/0x20
[ 66.777614] </TASK>

[ 66.777643] Allocated by task 10:
[ 66.777646] kasan_save_stack+0x39/0x60
[ 66.777649] kasan_save_track+0x14/0x40
[ 66.777652] kasan_save_alloc_info+0x37/0x50
[ 66.777655] __kasan_kmalloc+0xbb/0xc0
[ 66.777658] __kmalloc_cache_noprof+0x1c8/0x4b0
[ 66.777661] dm_dp_add_mst_connector+0xdd/0x5c0 [amdgpu]
[ 66.777880] drm_dp_mst_port_add_connector+0x47e/0x770 [drm_display_helper]
[ 66.777892] drm_dp_send_link_address+0x1554/0x2bf0 [drm_display_helper]
[ 66.777901] drm_dp_check_and_send_link_address+0x187/0x1f0 [drm_display_helper]
[ 66.777909] drm_dp_mst_link_probe_work+0x2b8/0x410 [drm_display_helper]
[ 66.777917] process_one_work+0x86b/0x1510
[ 66.777919] worker_thread+0x5c0/0xfa0
[ 66.777922] kthread+0x3a2/0x840
[ 66.777925] ret_from_fork+0x40/0x90
[ 66.777927] ret_from_fork_asm+0x11/0x20

[ 66.777932] Freed by task 1713:
[ 66.777935] kasan_save_stack+0x39/0x60
[ 66.777938] kasan_save_track+0x14/0x40
[ 66.777940] kasan_save_free_info+0x3b/0x60
[ 66.777944] __kasan_slab_free+0x52/0x70
[ 66.777946] kfree+0x13f/0x4b0
[ 66.777949] dm_dp_mst_connector_destroy+0xfa/0x150 [amdgpu]
[ 66.778179] drm_connector_free+0x7d/0xb0
[ 66.778184] drm_mode_object_put.part.0+0xee/0x160
[ 66.778188] drm_mode_object_put+0x37/0x50
[ 66.778191] drm_atomic_state_default_clear+0x220/0xd60
[ 66.778194] __drm_atomic_state_free+0x16e/0x2a0
[ 66.778197] drm_mode_atomic_ioctl+0x15ed/0x2ba0
[ 66.778200] drm_ioctl_kernel+0x17a/0x310
[ 66.778203] drm_ioctl+0x584/0xd10
[ 66.778206] amdgpu_drm_ioctl+0xd2/0x1c0 [amdgpu]
[ 66.778375] __x64_sys_ioctl+0x139/0x1a0
[ 66.778378] x64_sys_call+0xee7/0xfb0
[ 66.778381]
---truncated---