# CVE-2026-93237: LoongArch: Add DIRECT_MAP_PHYSMEM_END definition

CVE-2026-93237 is fixed in linux on 1 platform by DEBIAN-CVE-2026-93237 (version 7.2.6-1), released September 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-93237
- Priority: High
- CVSS: 7.8 (Moderate)
- EPSS: 0.0017
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 24, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-93237

## Description

In the Linux kernel, the following vulnerability has been resolved:  LoongArch: Add DIRECT_MAP_PHYSMEM_END definition  get_free_mem_region() and mhp_get_pluggable_range() bound their search to DIRECT_MAP_PHYSMEM_END. LoongArch does not define it, so the fallback in include/linux/mm.h applies: under CONFIG_SPARSEMEM_VMEMMAP it is (1ULL << MAX_PHYSMEM_BITS) - 1, a compile-time constant that does not adapt to the CPU's physical address space bits (cpu_pabits, probed from CPUCFG1).  The vmemmap window only covers physical space below 2^(cpu_pabits+1) (i.e. VMEMMAP_SIZE), so on CPUs with fewer physical address bits than MAX_PHYSMEM_BITS the fallback allows get_free_mem_region() to return a ZONE_DEVICE region outside the vmemmap window; vmemmap_populate() then wraps the memmap range around and maps it into low memory, silently corrupting the page tables. The same search also picked the top-of- address-space region that crashed memmap_init_zone_device() with amdkfd on Loongson-3C6000 in 6.16 [1]; the commit 2969b42c8f99 ("LoongArch/mm: align vmemmap to maximal folio size") keeps that region in bounds on current Loongson-3C6000 configs, but CPUs with smaller cpu_pabits (e.g. the Loongson-2K series) are still affected.  Define DIRECT_MAP_PHYSMEM_END as the vmemmap-covered physical range, (1ULL << (cpu_pabits + 1)) - 1, capped at (1ULL << MAX_PHYSMEM_BITS) - 1 under CONFIG_SPARSEMEM, similar to the commit f3336b48cf9d ("riscv: mm: Define DIRECT_MAP_PHYSMEM_END").  [1] https://lore.kernel.org/amd-gfx/20250814032153.227285-1-jeffbai@aosc.io/

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.2.6-1 | [DEBIAN-CVE-2026-93237](https://patchblox.com/security/data/fix/linux/debian-cve-2026-93237.md) | Sep 24, 2026 |

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