published September 24, 2026
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.