linux-kernel - [PATCH v5 08/17] arm: pgtable: move pagetable_dtor() to __tlb_remove

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Message-Id: <327b4b8990729edd4ce97d9d5acbdaff2d9fa1d1.1736317725.git.zhengqi.arch@bytedance.com>
Date: Wed,  8 Jan 2025 14:57:24 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
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	Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH v5 08/17] arm: pgtable: move pagetable_dtor() to __tlb_remove_table()

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.arch@...edance.com>
Suggested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Kevin Brodsky <kevin.brodsky@....com>
Cc: linux-arm-kernel@...ts.infradead.org
---
 arch/arm/include/asm/tlb.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index ef79bf1e8563f..59854c6b97bc5 100644
--- a/arch/arm/include/asm/tlb.h
+++ b/arch/arm/include/asm/tlb.h
@@ -26,12 +26,14 @@
 
 #else /* !CONFIG_MMU */
 
-#include <linux/swap.h>
 #include <asm/tlbflush.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);
 }
 
 #include <asm-generic/tlb.h>
@@ -41,7 +43,9 @@ __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, unsigned long addr)
 {
 	struct ptdesc *ptdesc = page_ptdesc(pte);
 
+#ifndef CONFIG_MMU_GATHER_TABLE_FREE
 	pagetable_dtor(ptdesc);
+#endif
 
 #ifndef CONFIG_ARM_LPAE
 	/*
@@ -61,7 +65,6 @@ __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmdp, unsigned long addr)
 #ifdef CONFIG_ARM_LPAE
 	struct ptdesc *ptdesc = virt_to_ptdesc(pmdp);
 
-	pagetable_dtor(ptdesc);
 	tlb_remove_ptdesc(tlb, ptdesc);
 #endif
 }
-- 
2.20.1