CVE-2026-93239arm64: mm: Fix the lockless page-table walk in show_pte()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b8f06b73ad146d84a33c124563c93eeef4f5b674
• https://git.kernel.org/stable/c/b3535b6cb2c48f97b8c3378eb9ea12538425bf14
• https://git.kernel.org/stable/c/e1b06278a7e241da0cd3187871e67255f956d184
• https://git.kernel.org/stable/c/08d931a0a850ad16a64f2cd23a19f40795cdbdf7
• https://git.kernel.org/stable/c/b28fe65a36b8209b6adcf2722c7ce974cf9ac8d1
• https://git.kernel.org/stable/c/68cbd70795dd8c06e7ccdc4eb0b74c5b180076c3
• https://git.kernel.org/stable/c/0f05d95b99164a9ccc4cf4a4920e0ff0228138ad
• https://git.kernel.org/stable/c/a77644d009dece1104b6fcc6e322b0e4503db0d6