{"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:\n\npowerpc/64s/slb: Fix SLB multihit issue during SLB preload\n\nOn systems using the hash MMU, there is a software SLB preload cache that\nmirrors 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","slug":"CVE-2025-71078","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\npowerpc/64s/slb: Fix SLB multihit issue during SLB preload\n\nOn systems using the hash MMU, there is a software SLB preload cache that\nmirrors the entries loaded into the hardware SLB buffer. This preload\ncache is subject to periodic eviction — typically after every 256 context\nswitches — to remove old entry.\n\nTo optimize performance, the kernel skips switch_mmu_context() in\nswitch_mm_irqs_off() when the prev and next mm_struct are the same.\nHowever, on hash MMU systems, this can lead to inconsistencies between\nthe hardware SLB and the software preload cache.\n\nIf an SLB entry for a process is evicted from the software cache on one\nCPU, and the same process later runs on another CPU without executing\nswitch_mmu_context(), the hardware SLB may retain stale entries. If the\nkernel then attempts to reload that entry, it can trigger an SLB\nmulti-hit error.\n\nThe following timeline shows how stale SLB entries are created and can\ncause a multi-hit error when a process moves between CPUs without a\nMMU context switch.\n\nCPU 0 CPU 1\n----- -----\nProcess P\nexec swapper/1\n load_elf_binary\n begin_new_exc\n activate_mm\n switch_mm_irqs_off\n switch_mmu_context\n switch_slb\n /*\n * This invalidates all\n * the entries in the HW\n * and setup the new HW\n * SLB entries as per the\n * preload cache.\n */\ncontext_switch\nsched_migrate_task migrates process P to cpu-1\n\nProcess swapper/0 context switch (to process P)\n(uses mm_struct of Process P) switch_mm_irqs_off()\n switch_slb\n load_slb++\n /*\n * load_slb becomes 0 here\n * and we evict an entry from\n * the preload cache with\n * preload_age(). We still\n * keep HW SLB and preload\n * cache in sync, that is\n * because all HW SLB entries\n * anyways gets evicted in\n * switch_slb during SLBIA.\n * We then only add those\n * entries back in HW SLB,\n * which are currently\n * present in preload_cache\n * (after eviction).\n */\n load_elf_binary continues...\n setup_new_exec()\n slb_setup_new_exec()\n\n sched_switch event\n sched_migrate_task migrates\n process P to cpu-0\n\ncontext_switch from swapper/0 to Process P\n switch_mm_irqs_off()\n /*\n * Since both prev and next mm struct are same we don't call\n * switch_mmu_context(). This will cause the HW SLB and SW preload\n * cache to go out of sync in preload_new_slb_context. Because there\n * was an SLB entry which was evicted from both HW and preload cache\n * on cpu-1. Now later in preload_new_slb_context(), when we will try\n * to add the same preload entry again, we will add this to the SW\n * preload cache and then will add it to the HW SLB. Since on cpu-0\n * this entry was never invalidated, hence adding this entry to the HW\n * SLB will cause a SLB multi-hit error.\n */\nload_elf_binary cont\n---truncated---\n\n## Affected\n\n- `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 01324c0328181b94cf390bda22ff91c75126ea57`\n- `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 2e9a95d60f1df7b57618fd5ef057aef331575bd2`\n- `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < c9f865022a1823d814032a09906e91e4701a35fc`\n- `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < b13a3dbfa196af68eae2031f209743735ad416bf`\n- `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 895123c309a34d2cfccf7812b41e17261a3a6f37`\n- `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 4ae1e46d8a290319f33f71a2710a1382ba5431e8`\n- `Linux >= 5434ae74629af58ad0fc27143a9ea435f7734410 < 00312419f0863964625d6dcda8183f96849412c6`\n- `Linux 4.20`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}