CVE-2023-53112

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

drm/i915/sseu: fix max_subslices array-index-out-of-bounds access

It seems that commit bc3c5e0809ae ("drm/i915/sseu: Don't try to store EU mask internally in UAPI format") exposed a potential out-of-bounds access, reported by UBSAN as following on a laptop with a gen 11 i915 card:

UBSAN: array-index-out-of-bounds in drivers/gpu/drm/i915/gt/intel_sseu.c:65:27 index 6 is out of range for type 'u16 [6]' CPU: 2 PID: 165 Comm: systemd-udevd Not tainted 6.2.0-9-generic #9-Ubuntu Hardware name: Dell Inc. XPS 13 9300/077Y9N, BIOS 1.11.0 03/22/2022 Call Trace: <TASK> show_stack+0x4e/0x61 dump_stack_lvl+0x4a/0x6f dump_stack+0x10/0x18 ubsan_epilogue+0x9/0x3a __ubsan_handle_out_of_bounds.cold+0x42/0x47 gen11_compute_sseu_info+0x121/0x130 [i915] intel_sseu_info_init+0x15d/0x2b0 [i915] intel_gt_init_mmio+0x23/0x40 [i915] i915_driver_mmio_probe+0x129/0x400 [i915] ? intel_gt_probe_all+0x91/0x2e0 [i915] i915_driver_probe+0xe1/0x3f0 [i915] ? drm_privacy_screen_get+0x16d/0x190 [drm] ? acpi_dev_found+0x64/0x80 i915_pci_probe+0xac/0x1b0 [i915] ...

According to the definition of sseu_dev_info, eu_mask->hsw is limited to a maximum of GEN_MAX_SS_PER_HSW_SLICE (6) sub-slices, but gen11_sseu_info_init() can potentially set 8 sub-slices, in the !IS_JSL_EHL(gt->i915) case.

Fix this by reserving up to 8 slots for max_subslices in the eu_mask struct.

(cherry picked from commit 3cba09a6ac86ea1d456909626eb2685596c07822)

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.