[PATCH bpf-next] arm64: mm: Complete the PTE store in ptep_try_set()

[Tejun Heo]

ptep_try_set() installs the new entry with try_cmpxchg() but, unlike
__set_pte(), never calls __set_pte_complete(). On arm64, installing a valid
kernel PTE requires barriers afterward so a subsequent access observes it.
Without them the access can fault instead of reaching the freshly installed
page.

Call __set_pte_complete() after a successful cmpxchg, mirroring
__set_pte().

Fixes: 258df8fce42f ("mm: Add ptep_try_set() for lockless empty-slot installs")
Suggested-by: Catalin Marinas <catalin.marinas at arm.com>
Link: https://lore.kernel.org/all/aiRFcz78QTZdIHHB@arm.com/
Signed-off-by: Tejun Heo <tj at kernel.org>
---
 arch/arm64/include/asm/pgtable.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 3ce0f2a6cab6..dc8525431273 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1838,7 +1838,11 @@ 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;
+
+	__set_pte_complete(new_pte);
+	return true;
 }
 #define ptep_try_set ptep_try_set
 
-- 
2.51.1