Bug 2414498 (CVE-2025-40174)

Summary: CVE-2025-40174 kernel: x86/mm: Fix SMP ordering in switch_mm_irqs_off()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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flaw was found in the Linux kernel’s x86 memory‐management subsystem (function switch_mm_irqs_off()). Due to a missing smp_mb() memory‐barrier between the loaded_mm store and the tlb_gen load, the ordering of TLB (Translation Lookaside Buffer) flush operations can be violated in SMP systems. This may cause switch_mm() to not observe a recent tlb_gen update and fail to flush the TLBs properly.
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Description OSIDB Bzimport 2025-11-12 11:03:43 UTC 
In the Linux kernel, the following vulnerability has been resolved:

x86/mm: Fix SMP ordering in switch_mm_irqs_off()

Stephen noted that it is possible to not have an smp_mb() between
the loaded_mm store and the tlb_gen load in switch_mm(), meaning the
ordering against flush_tlb_mm_range() goes out the window, and it
becomes possible for switch_mm() to not observe a recent tlb_gen
update and fail to flush the TLBs.

[ dhansen: merge conflict fixed by Ingo ]
Comment 1 Alexander B 2025-11-13 14:25:58 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025111255-CVE-2025-40174-b076@gregkh/T