CVE-2023-52856

CVE-2023-52856 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Description

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: Toradex Verdin AM62 on Verdin Development Board (DT) pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : drm_connector_cleanup+0x78/0x2d4 [drm] lr : lt8912_bridge_detach+0x54/0x6c [lontium_lt8912b] sp : ffff800082ed3a90 x29: ffff800082ed3a90 x28: ffff0000040c1940 x27: 0000000000000000 x26: 0000000000000000 x25: dead000000000122 x24: dead000000000122 x23: dead000000000100 x22: ffff000003fb6388 x21: 0000000000000000 x20: 0000000000000000 x19: ffff000003fb6260 x18: fffffffffffe56e8 x17: 0000000000000000 x16: 0010000000000000 x15: 0000000000000038 x14: 0000000000000000 x13: ffff800081914b48 x12: 000000000000040e x11: 000000000000015a x10: ffff80008196ebb8 x9 : ffff800081914b48 x8 : 00000000ffffefff x7 : ffff0000040c1940 x6 : ffff80007aa649d0 x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff80008159e008 x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000 Call trace: drm_connector_cleanup+0x78/0x2d4 [drm] lt8912_bridge_detach+0x54/0x6c [lontium_lt8912b] drm_bridge_detach+0x44/0x84 [drm] drm_encoder_cleanup+0x40/0xb8 [drm] drmm_encoder_alloc_release+0x1c/0x30 [drm] drm_managed_release+0xac/0x148 [drm] drm_dev_put.part.0+0x88/0xb8 [drm] devm_drm_dev_init_release+0x14/0x24 [drm] devm_action_release+0x14/0x20 release_nodes+0x5c/0x90 devres_release_all+0x8c/0xe0 device_unbind_cleanup+0x18/0x68 device_release_driver_internal+0x208/0x23c driver_detach+0x4c/0x94 bus_remove_driver+0x70/0xf4 driver_unregister+0x30/0x60 platform_driver_unregister+0x14/0x20 tidss_platform_driver_exit+0x18/0xb2c [tidss] __arm64_sys_delete_module+0x1a0/0x2b4 invoke_syscall+0x48/0x110 el0_svc_common.constprop.0+0x60/0x10c do_el0_svc_compat+0x1c/0x40 el0_svc_compat+0x40/0xac el0t_32_sync_handler+0xb0/0x138 el0t_32_sync+0x194/0x198 Code: 9104a276 f2fbd5b7 aa0203e1 91008af8 (f85c0420)

Frequently asked questions

What is CVE-2023-52856?
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: Toradex Verdin AM62 on Verdin Development Board (DT) pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : drm_connector_cleanup+0x78/0x2d4 [drm] lr : lt8912_bridge_detach+0x54/0x6c [lontium_lt8912b] sp : ffff800082ed3a90 x29: ffff800082ed3a90 x28: ffff0000040c1940 x27: 0000000000000000 x26: 0000000000000000 x25: dead000000000122 x24: dead000000000122 x23: dead000000000100 x22: ffff000003fb6388 x21: 0000000000000000 x20: 0000000000000000 x19: ffff000003fb6260 x18: fffffffffffe56e8 x17: 0000000000000000 x16: 0010000000000000 x15: 0000000000000038 x14: 0000000000000000 x13: ffff800081914b48 x12: 000000000000040e x11: 000000000000015a x10: ffff80008196ebb8 x9 : ffff800081914b48 x8 : 00000000ffffefff x7 : ffff0000040c1940 x6 : ffff80007aa649d0 x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff80008159e008 x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000 Call trace: drm_connector_cleanup+0x78/0x2d4 [drm] lt8912_bridge_detach+0x54/0x6c [lontium_lt8912b] drm_bridge_detach+0x44/0x84 [drm] drm_encoder_cleanup+0x40/0xb8 [drm] drmm_encoder_alloc_release+0x1c/0x30 [drm] drm_managed_release+0xac/0x148 [drm] drm_dev_put.part.0+0x88/0xb8 [drm] devm_drm_dev_init_release+0x14/0x24 [drm] devm_action_release+0x14/0x20 release_nodes+0x5c/0x90 devres_release_all+0x8c/0xe0 device_unbind_cleanup+0x18/0x68 device_release_driver_internal+0x208/0x23c driver_detach+0x4c/0x94 bus_remove_driver+0x70/0xf4 driver_unregister+0x30/0x60 platform_driver_unregister+0x14/0x20 tidss_platform_driver_exit+0x18/0xb2c [tidss] __arm64_sys_delete_module+0x1a0/0x2b4 invoke_syscall+0x48/0x110 el0_svc_common.constprop.0+0x60/0x10c do_el0_svc_compat+0x1c/0x40 el0_svc_compat+0x40/0xac el0t_32_sync_handler+0xb0/0x138 el0t_32_sync+0x194/0x198 Code: 9104a276 f2fbd5b7 aa0203e1 91008af8 (f85c0420)
How severe is CVE-2023-52856?
CVE-2023-52856 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2023-52856 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (14th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-52856?
CVE-2023-52856 affects Linux Linux Kernel. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-52856?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2023-52856 have an EU (EUVD) identifier?
Yes. CVE-2023-52856 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2023-59569.
When was CVE-2023-52856 published?
CVE-2023-52856 was published on 2024-05-21 and last updated on 2026-06-17.

References

Affected products (1)

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