arm64: mm: Fix the lockless page-table walk in show_pte()

Summary

In the Linux kernel, the following vulnerability has been resolved: arm64: mm: Fix the lockless page-table walk in show_pte() show_pte() walks page tables locklessly and can run with interrupts enabled. A concurrent teardown can free a table page while it is being walked. It can also clear a parent entry after show_pte() checked it; the regular pXd_offset() helpers then reread the cleared entry and can derive a bogus lower-level pointer and fault again. Use the lockless offset helpers with the saved parent entries, as gup_fast() does, and pass the saved PMD to pte_offset_map(). For task page tables, arm64 selects MMU_GATHER_RCU_TABLE_FREE. Disable local interrupts around the walk to hold off RCU-deferred table frees and block the tlb_remove_table_sync_one() IPI until the walk is finished. Place the IRQ guard after the header print. This does not make the output a consistent snapshot, but prevents the task page-table walk from dereferencing a released table page or deriving a pointer from a different parent value.

Timeline

1. Sep 24, 2026, 3:34 PM UTCCVE published
2. Oct 19, 2026, 9:07 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 1d18c47c735e8adfe531fc41fae31e98f86b68fe · fixed in 08d931a0a850ad16a64f2cd23a19f40795cdbdf7; From 1d18c47c735e8adfe531fc41fae31e98f86b68fe · fixed in b28fe65a36b8209b6adcf2722c7ce974cf9ac8d1; From 1d18c47c735e8adfe531fc41fae31e98f86b68fe · fixed in 68cbd70795dd8c06e7ccdc4eb0b74c5b180076c3; From 1d18c47c735e8adfe531fc41fae31e98f86b68fe · fixed in 0f05d95b99164a9ccc4cf4a4920e0ff0228138ad; From 1d18c47c735e8adfe531fc41fae31e98f86b68fe · fixed in a77644d009dece1104b6fcc6e322b0e4503db0d6

• Linux Linux

  3.7

• KernelLinux

  From 3.7.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.51; From 6.19.0 · fixed in 7.2.5

References 5