[PATCH v1] arm64: tlb: fix the TTL value of tlb_get_level

[Zhenyu Ye]

The TTL field indicates the level of page table walk holding the *leaf*
entry for the address being invalidated. But currently, the TTL field
may be set to an incorrent value in the following stack:

pte_free_tlb
    __pte_free_tlb
        tlb_remove_table
            tlb_table_invalidate
                tlb_flush_mmu_tlbonly
                    tlb_flush

In this case, we just want to flush a PTE page, but the tlb->cleared_pmds
is set and we get tlb_level = 2 in the tlb_get_level() function. This may
cause some unexpected problems.

This patch set the TTL field to 0 if tlb->freed_tables is set. The
tlb->freed_tables indicates page table pages are freed, not the leaf
entry.

Fixes: c4ab2cbc1d87 ("arm64: tlb: Set the TTL field in flush_tlb_range")
Reported-by: ZhuRui <zhurui3@xxxxxxxxxx>
Signed-off-by: Zhenyu Ye <yezhenyu2@xxxxxxxxxx>
---
 arch/arm64/include/asm/tlb.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index 61c97d3b58c7..c995d1f4594f 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -28,6 +28,10 @@ static void tlb_flush(struct mmu_gather *tlb);
  */
 static inline int tlb_get_level(struct mmu_gather *tlb)
 {
+	/* The TTL field is only valid for the leaf entry. */
+	if (tlb->freed_tables)
+		return 0;
+
 	if (tlb->cleared_ptes && !(tlb->cleared_pmds ||
 				   tlb->cleared_puds ||
 				   tlb->cleared_p4ds))
-- 
2.26.2