Linux Kernel Alpha TLB Shootdown Bug Causing Heap Corruption
CVE-2026-43258 Published on May 6, 2026
alpha: fix user-space corruption during memory compaction
In the Linux kernel, the following vulnerability has been resolved:
alpha: fix user-space corruption during memory compaction
Alpha systems can suffer sporadic user-space crashes and heap
corruption when memory compaction is enabled.
Symptoms include SIGSEGV, glibc allocator failures (e.g. "unaligned
tcache chunk"), and compiler internal errors. The failures disappear
when compaction is disabled or when using global TLB invalidation.
The root cause is insufficient TLB shootdown during page migration.
Alpha relies on ASN-based MM context rollover for instruction cache
coherency, but this alone is not sufficient to prevent stale data or
instruction translations from surviving migration.
Fix this by introducing a migration-specific helper that combines:
- MM context invalidation (ASN rollover),
- immediate per-CPU TLB invalidation (TBI),
- synchronous cross-CPU shootdown when required.
The helper is used only by migration/compaction paths to avoid changing
global TLB semantics.
Additionally, update flush_tlb_other(), pte_clear(), to use
READ_ONCE()/WRITE_ONCE() for correct SMP memory ordering.
This fixes observed crashes on both UP and SMP Alpha systems.
Products Associated with CVE-2026-43258
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Affected Versions
Linux:- Version a48d07afdf18212de22b959715b16793c5a6e57a and below d4ca6ca2c6f5a1d19d9014c5b36d96637846b5d6 is affected.
- Version a48d07afdf18212de22b959715b16793c5a6e57a and below 03e42b5f7ad4c2c3db8bd384bab7990d5d53c90f is affected.
- Version a48d07afdf18212de22b959715b16793c5a6e57a and below bab8d762a8dbb816b10011e13b87d1bca91e5f77 is affected.
- Version a48d07afdf18212de22b959715b16793c5a6e57a and below dd5712f3379cfe760267cdd28ff957d9ab4e51c7 is affected.
- Version 2.6.16 is affected.
- Before 2.6.16 is unaffected.
- Version 6.12.75, <= 6.12.* is unaffected.
- Version 6.18.16, <= 6.18.* is unaffected.
- Version 6.19.6, <= 6.19.* is unaffected.
- Version 7.0, <= * is unaffected.