CVE-2025-71078
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-03-25

Assigner: kernel.org

Description
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---
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Meta Information
Published
2026-01-13
Last Modified
2026-03-25
Generated
2026-05-07
AI Q&A
2026-01-14
EPSS Evaluated
2026-05-05
NVD
CVE-2025-71078
Affected Vendors & Products
Showing 15 associated CPEs
Vendor Product Version / Range
linux linux_kernel 4.20
linux linux_kernel From 5.11 (inc) to 5.15.198 (exc)
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 6.13 (inc) to 6.18.4 (exc)
linux linux_kernel From 5.16 (inc) to 6.1.160 (exc)
linux linux_kernel From 6.2 (inc) to 6.6.120 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.64 (exc)
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel 6.19
linux linux_kernel From 4.20.1 (inc) to 5.10.248 (exc)
Helpful Resources
Exploitability
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the Linux kernel on systems using the hash MMU with a software SLB preload cache. The preload cache mirrors entries in the hardware SLB buffer but is periodically evicted to remove old entries. To optimize performance, the kernel sometimes skips a context switch operation when the memory management structures are the same between processes. However, this can cause inconsistencies between the hardware SLB and the software preload cache. Specifically, if an SLB entry is evicted from the software cache on one CPU and the same process runs on another CPU without a proper MMU context switch, the hardware SLB may retain stale entries. When the kernel tries to reload these entries, it can cause an SLB multi-hit error, which is a conflict due to duplicate entries in the hardware SLB.


How can this vulnerability impact me? :

This vulnerability can lead to SLB multi-hit errors on affected systems, which may cause system instability or crashes when processes migrate between CPUs without proper MMU context switching. This can degrade system reliability and performance on systems using the hash MMU and affected Linux kernel versions.


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