CVE-2023-52856 — drm/bridge: lt8912b: Fix crash on bridge detach

Affected: Linux

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

drm/bridge: lt8912b: Fix crash on bridge detach

The lt8912b driver, in its bridge detach function, calls drm_connector_unregister() and drm_connector_cleanup().

drm_connector_unregister() should be called only for connectors explicitly registered with drm_connector_register(), which is not the case in lt8912b.

The driver's drm_connector_funcs.destroy hook is set to drm_connector_cleanup().

Thus the driver should not call either drm_connector_unregister() nor drm_connector_cleanup() in its lt8912_bridge_detach(), as they cause a crash on bridge detach:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Mem abort info: ESR = 0x0000000096000006 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x06: level 2 translation fault Data abort info: ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 user pgtable: 4k pages, 48-bit VAs, pgdp=00000000858f3000 [0000000000000000] pgd=0800000085918003, p4d=0800000085918003, pud=0800000085431003, pmd=0000000000000000 Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP Modules linked in: tidss(-) display_connector lontium_lt8912b tc358768 panel_lvds panel_simple drm_dma_helper drm_kms_helper drm drm_panel_orientation_quirks CPU: 3 PID: 462 Comm: rmmod Tainted: G W 6.5.0-rc2+ #2 Hardware name:…

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CVE-2023-52856 — drm/bridge: lt8912b: Fix crash on bridge detach