CVE-2026-93237
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
The Linux kernel for the LoongArch architecture lacks a DIRECT_MAP_PHYSMEM_END definition, causing get_free_mem_region() and mhp_get_pluggable_range() to potentially return ZONE_DEVICE regions outside the vmemmap window. This can lead to page table corruption or system crashes, especially on CPUs with fewer physical address bits, such as the Loongson-2K series.
Risk Assessment
The risk involves possible memory corruption and system crashes, particularly when using ZONE_DEVICE (e.g., with amdkfd). This could lead to unexpected system behavior or destabilization.
Recommendation
It is recommended to update the Linux kernel as soon as possible to a version that includes the fix defining DIRECT_MAP_PHYSMEM_END for LoongArch. Monitor security patch releases and apply them in production environments.
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Original NVD description (English source)
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/[email protected]/
Vulnerability data from NVD (NIST) · CISA KEV · EPSS