From 71385b78dbc290328e3b04ebd9b27786642afaca Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sun, 7 Jun 2026 21:25:47 -1000 Subject: [PATCH] arm64: mm: Complete the PTE store in ptep_try_set() ptep_try_set() installs a kernel PTE with try_cmpxchg() but, unlike __set_pte(), skips the barriers that arm64 requires after writing a valid kernel PTE. Without them a subsequent access can fault instead of seeing the new mapping. Issue them with emit_pte_barriers() rather than __set_pte_complete(). ptep_try_set() must finish the store before it returns, but __set_pte_complete() would defer the barriers when the calling context is in lazy MMU mode. v2: Emit the barriers directly instead of __set_pte_complete(). (Catalin) Fixes: 258df8fce42f ("mm: Add ptep_try_set() for lockless empty-slot installs") Suggested-by: Catalin Marinas Signed-off-by: Tejun Heo Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/all/aiRFcz78QTZdIHHB@arm.com/ Link: https://lore.kernel.org/bpf/7f5f7c94601312c1a401fb18998291cc@kernel.org Signed-off-by: Kumar Kartikeya Dwivedi --- arch/arm64/include/asm/pgtable.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 3ce0f2a6cab6..3e579c26b383 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1838,7 +1838,16 @@ static inline bool ptep_try_set(pte_t *ptep, pte_t new_pte) { pteval_t old = 0; - return try_cmpxchg(&pte_val(*ptep), &old, pte_val(new_pte)); + if (!try_cmpxchg(&pte_val(*ptep), &old, pte_val(new_pte))) + return false; + + /* + * The store must be complete by the time this returns, but the caller + * may be in lazy MMU mode, where __set_pte_complete() would defer the + * barriers. Issue them directly. + */ + emit_pte_barriers(); + return true; } #define ptep_try_set ptep_try_set