--- id: CVE-2025-71078 title: 'powerpc/64s/slb: Fix SLB multihit issue during SLB preload' summary: |- In the Linux kernel, the following vulnerability has been resolved: powerpc/64s/slb: Fix SLB multihit issue during SLB preload On systems using the hash MMU, there is a software SLB preload cache that mirrors the entries loaded into th… severity: high cvss: 7.8 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H' cvssSource: cna vendor: Linux product: Linux affected: - >- Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 01324c0328181b94cf390bda22ff91c75126ea57 - >- Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 2e9a95d60f1df7b57618fd5ef057aef331575bd2 - >- Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < c9f865022a1823d814032a09906e91e4701a35fc - >- Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < b13a3dbfa196af68eae2031f209743735ad416bf - >- Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 895123c309a34d2cfccf7812b41e17261a3a6f37 - >- Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 4ae1e46d8a290319f33f71a2710a1382ba5431e8 - >- Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 00312419f0863964625d6dcda8183f96849412c6 - Linux 4.20 ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-10-16T15:05:39.588741Z' published: '2026-01-13' updated: '2026-10-16' sourceUpdated: '2026-10-16T15:09:46.080Z' source: CVEORG sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-71078' references: - url: 'https://git.kernel.org/stable/c/01324c0328181b94cf390bda22ff91c75126ea57' - url: 'https://git.kernel.org/stable/c/2e9a95d60f1df7b57618fd5ef057aef331575bd2' - url: 'https://git.kernel.org/stable/c/c9f865022a1823d814032a09906e91e4701a35fc' - url: 'https://git.kernel.org/stable/c/b13a3dbfa196af68eae2031f209743735ad416bf' - url: 'https://git.kernel.org/stable/c/895123c309a34d2cfccf7812b41e17261a3a6f37' - url: 'https://git.kernel.org/stable/c/4ae1e46d8a290319f33f71a2710a1382ba5431e8' - url: 'https://git.kernel.org/stable/c/00312419f0863964625d6dcda8183f96849412c6' tags: - cve.org epss: 0.00144 epssPercentile: 0.03307 ingestedAt: '2026-10-16T17:24:46.635Z' --- ## Overview In the Linux kernel, the following vulnerability has been resolved: powerpc/64s/slb: Fix SLB multihit issue during SLB preload On systems using the hash MMU, there is a software SLB preload cache that mirrors the entries loaded into the hardware SLB buffer. This preload cache is subject to periodic eviction — typically after every 256 context switches — to remove old entry. To optimize performance, the kernel skips switch_mmu_context() in switch_mm_irqs_off() when the prev and next mm_struct are the same. However, on hash MMU systems, this can lead to inconsistencies between the hardware SLB and the software preload cache. If an SLB entry for a process is evicted from the software cache on one CPU, and the same process later runs on another CPU without executing switch_mmu_context(), the hardware SLB may retain stale entries. If the kernel then attempts to reload that entry, it can trigger an SLB multi-hit error. The following timeline shows how stale SLB entries are created and can cause a multi-hit error when a process moves between CPUs without a MMU context switch. CPU 0 CPU 1 ----- ----- Process P exec swapper/1 load_elf_binary begin_new_exc activate_mm switch_mm_irqs_off switch_mmu_context switch_slb /* * This invalidates all * the entries in the HW * and setup the new HW * SLB entries as per the * preload cache. */ context_switch sched_migrate_task migrates process P to cpu-1 Process swapper/0 context switch (to process P) (uses mm_struct of Process P) switch_mm_irqs_off() switch_slb load_slb++ /* * load_slb becomes 0 here * and we evict an entry from * the preload cache with * preload_age(). We still * keep HW SLB and preload * cache in sync, that is * because all HW SLB entries * anyways gets evicted in * switch_slb during SLBIA. * We then only add those * entries back in HW SLB, * which are currently * present in preload_cache * (after eviction). */ load_elf_binary continues... setup_new_exec() slb_setup_new_exec() sched_switch event sched_migrate_task migrates process P to cpu-0 context_switch from swapper/0 to Process P switch_mm_irqs_off() /* * Since both prev and next mm struct are same we don't call * switch_mmu_context(). This will cause the HW SLB and SW preload * cache to go out of sync in preload_new_slb_context. Because there * was an SLB entry which was evicted from both HW and preload cache * on cpu-1. Now later in preload_new_slb_context(), when we will try * to add the same preload entry again, we will add this to the SW * preload cache and then will add it to the HW SLB. Since on cpu-0 * this entry was never invalidated, hence adding this entry to the HW * SLB will cause a SLB multi-hit error. */ load_elf_binary cont ---truncated--- ## Affected - `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 01324c0328181b94cf390bda22ff91c75126ea57` - `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 2e9a95d60f1df7b57618fd5ef057aef331575bd2` - `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < c9f865022a1823d814032a09906e91e4701a35fc` - `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < b13a3dbfa196af68eae2031f209743735ad416bf` - `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 895123c309a34d2cfccf7812b41e17261a3a6f37` - `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 4ae1e46d8a290319f33f71a2710a1382ba5431e8` - `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 00312419f0863964625d6dcda8183f96849412c6` - `Linux 4.20` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges.