[PATCH v4 09/15] arm64: pgtable: move pagetable_dtor() to __tlb_remove_table()

[Qi Zheng]

Move pagetable_dtor() to __tlb_remove_table(), so that ptlock and page
table pages can be freed together (regardless of whether RCU is used).
This prevents the use-after-free problem where the ptlock is freed
immediately but the page table pages is freed later via RCU.

Page tables shouldn't have swap cache, so use pagetable_free() instead of
free_page_and_swap_cache() to free page table pages.

Signed-off-by: Qi Zheng <zhengqi.a...@bytedance.com>
Suggested-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: linux-arm-ker...@lists.infradead.org
---
 arch/arm64/include/asm/tlb.h | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index 408d0f36a8a8f..93591a80b5bfb 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -9,11 +9,13 @@
 #define __ASM_TLB_H
 
 #include <linux/pagemap.h>
-#include <linux/swap.h>
 
 static inline void __tlb_remove_table(void *_table)
 {
-       free_page_and_swap_cache((struct page *)_table);
+       struct ptdesc *ptdesc = (struct ptdesc *)_table;
+
+       pagetable_dtor(ptdesc);
+       pagetable_free(ptdesc);
 }
 
 #define tlb_flush tlb_flush
@@ -82,7 +84,6 @@ static inline void __pte_free_tlb(struct mmu_gather *tlb, 
pgtable_t pte,
 {
        struct ptdesc *ptdesc = page_ptdesc(pte);
 
-       pagetable_dtor(ptdesc);
        tlb_remove_ptdesc(tlb, ptdesc);
 }
 
@@ -92,7 +93,6 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, 
pmd_t *pmdp,
 {
        struct ptdesc *ptdesc = virt_to_ptdesc(pmdp);
 
-       pagetable_dtor(ptdesc);
        tlb_remove_ptdesc(tlb, ptdesc);
 }
 #endif
@@ -106,7 +106,6 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, 
pud_t *pudp,
        if (!pgtable_l4_enabled())
                return;
 
-       pagetable_dtor(ptdesc);
        tlb_remove_ptdesc(tlb, ptdesc);
 }
 #endif
@@ -120,7 +119,6 @@ static inline void __p4d_free_tlb(struct mmu_gather *tlb, 
p4d_t *p4dp,
        if (!pgtable_l5_enabled())
                return;
 
-       pagetable_dtor(ptdesc);
        tlb_remove_ptdesc(tlb, ptdesc);
 }
 #endif
-- 
2.20.1