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CVE-2025-37964

Vulnérabilité élevée dans Linux (Linux)

CVSS 7.8 · Élevée
EPSS 0.2%
Linux•Linux•Versions : <=6.1.*, 6.14.7, <=6.12.*, 3dbe889a1b829b4c07e0836ff853fe649e51ce4f, <=6.14.*, 6.6.91, 0, <6.12.29, b47002ed65ade940839b7f439ff4a194e7d5ec28, 6.14, <6.6.91, d1347977661342cb09a304a17701eb2d4aa21dec, <=6.6.*, 848b5815177582de0e1d0118725378e0fbadca20, 6.1.129, <d41072906abec8bb8e01ed16afefbaa558908c89, 6.12.16, <5.15.183, 5.15.183, a04fe3bfc71e28009e20357b79df1e8ef7c9d600, <fea4e317f9e7e1f449ce90dedc27a2d2a95bee5a, 6.12.29, 6.13.4, <399ec9ca8fc4999e676ff89a90184ec40031cf59, 6.15, 5.15.179, <02ad4ce144bd27f71f583f667fdf3b3ba0753477, <=*, 6db2526c1d694c91c6e05e2f186c085e9460f202, <6.1.139, <=5.15.*, <6.14, <12f703811af043d32b1c8a30001b2fa04d5cd0ac, <d87392094f96e162fa5fa5a8640d70cc0952806f, 6.1.139, 6.6.79

Description

In the Linux kernel, the following vulnerability has been resolved: x86/mm: Eliminate window where TLB flushes may be inadvertently skipped tl;dr: There is a window in the mm switching code where the new CR3 is set and the CPU should be getting TLB flushes for the new mm. But should_flush_tlb() has a bug and suppresses the flush. Fix it by widening the window where should_flush_tlb() sends an IPI. Long Version: === History === There were a few things leading up to this. First, updating mm_cpumask() was observed to be too expensive, so it was made lazier. But being lazy caused too many unnecessary IPIs to CPUs due to the now-lazy mm_cpumask(). So code was added to cull mm_cpumask() periodically[2]. But that culling was a bit too aggressive and skipped sending TLB flushes to CPUs that need them. So here we are again. === Problem === The too-aggressive code in should_flush_tlb() strikes in this window: // Turn on IPIs for this CPU/mm combination, but only // if should_flush_tlb() agrees: cpumask_set_cpu(cpu, mm_cpumask(next)); next_tlb_gen = atomic64_read(&next->context.tlb_gen); choose_new_asid(next, next_tlb_gen, &new_asid, &need_flush); load_new_mm_cr3(need_flush); // ^ After 'need_flush' is set to false, IPIs *MUST* // be sent to this CPU and not be ignored. this_cpu_write(cpu_tlbstate.loaded_mm, next); // ^ Not until this point does should_flush_tlb() // become true! should_flush_tlb() will suppress TLB flushes between load_new_mm_cr3() and writing to 'loaded_mm', which is a window where they should not be suppressed. Whoops. === Solution === Thankfully, the fuzzy "just about to write CR3" window is already marked with loaded_mm==LOADED_MM_SWITCHING. Simply checking for that state in should_flush_tlb() is sufficient to ensure that the CPU is targeted with an IPI. This will cause more TLB flush IPIs. But the window is relatively small and I do not expect this to cause any kind of measurable performance impact. Update the comment where LOADED_MM_SWITCHING is written since it grew yet another user. Peter Z also raised a concern that should_flush_tlb() might not observe 'loaded_mm' and 'is_lazy' in the same order that switch_mm_irqs_off() writes them. Add a barrier to ensure that they are observed in the order they are written.

Gravité et risque d'exploitation

CVE-2025-37964 obtient un score CVSS de 7.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.21 %, ce qui la place devant 10.5 % des CVE référencées.

Que faire ?

  • Vérifiez si Linux (versions <=6.1.*, 6.14.7, <=6.12.*, 3dbe889a1b829b4c07e0836ff853fe649e51ce4f, <=6.14.*, 6.6.91, 0, <6.12.29, b47002ed65ade940839b7f439ff4a194e7d5ec28, 6.14, <6.6.91, d1347977661342cb09a304a17701eb2d4aa21dec, <=6.6.*, 848b5815177582de0e1d0118725378e0fbadca20, 6.1.129, <d41072906abec8bb8e01ed16afefbaa558908c89, 6.12.16, <5.15.183, 5.15.183, a04fe3bfc71e28009e20357b79df1e8ef7c9d600, <fea4e317f9e7e1f449ce90dedc27a2d2a95bee5a, 6.12.29, 6.13.4, <399ec9ca8fc4999e676ff89a90184ec40031cf59, 6.15, 5.15.179, <02ad4ce144bd27f71f583f667fdf3b3ba0753477, <=*, 6db2526c1d694c91c6e05e2f186c085e9460f202, <6.1.139, <=5.15.*, <6.14, <12f703811af043d32b1c8a30001b2fa04d5cd0ac, <d87392094f96e162fa5fa5a8640d70cc0952806f, 6.1.139, 6.6.79) est présent sur votre parc.
  • Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
  • À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
  • Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

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