ACPI: video: Fix random crashes due to bad kfree()

ACPI: video: Fix random crashes due to bad kfree()

Commit c6a837088bed ("drm/amd/display: Fetch the EDID from _DDC if
available for eDP") added function dm_helpers_probe_acpi_edid(), which
fetches the EDID from the BIOS by calling acpi_video_get_edid().

acpi_video_get_edid() returns a pointer to the EDID, but this pointer
does not originate from kmalloc() - it is actually the internal
"pointer" field from an acpi_buffer struct (which did come from
kmalloc()).

dm_helpers_probe_acpi_edid() then attempts to kfree() the EDID pointer,
resulting in memory corruption which leads to random, intermittent
crashes (e.g. 4% of boots will fail with some Oops).

Fix this by allocating a new array (which can be safely freed) for the
EDID data, and correctly freeing the acpi_buffer pointer.

The only other caller of acpi_video_get_edid() is nouveau_acpi_edid():
remove the extraneous kmemdup() here as the EDID data is now copied in
acpi_video_device_EDID().

Signed-off-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Fixes: c6a837088bed ("drm/amd/display: Fetch the EDID from _DDC if available for eDP")
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Reported-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Borislav Petkov (AMD) <bp@alien8.de>
Closes: https://lore.kernel.org/amd-gfx/20250110175252.GBZ4FedNKqmBRaY4T3@fat_crate.local/T/#m324a23eb4c4c32fa7e89e31f8ba96c781e496fb1
Link: https://patch.msgid.link/Z4K_oQL7eA9Owkbs@debian.local
[ rjw: Changed function description comment into a kerneldoc one ]
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>