linux-kernel - [PATCH v2 06/15] arm: pgtable: move pagetable_dtor() to __tlb_remove

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Message-Id: <dd9808c1a850a0b9974355b51182e2c98fe29c91.1734526570.git.zhengqi.arch@bytedance.com>
Date: Wed, 18 Dec 2024 21:04:42 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: peterz@...radead.org,
	tglx@...utronix.de,
	david@...hat.com,
	jannh@...gle.com,
	hughd@...gle.com,
	yuzhao@...gle.com,
	willy@...radead.org,
	muchun.song@...ux.dev,
	vbabka@...nel.org,
	lorenzo.stoakes@...cle.com,
	akpm@...ux-foundation.org,
	rientjes@...gle.com,
	vishal.moola@...il.com
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Qi Zheng <zhengqi.arch@...edance.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v2 06/15] 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>
Cc: linux-arm-kernel@...ts.infradead.org
---
 arch/arm/include/asm/tlb.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index ef79bf1e8563f..264ab635e807a 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>
@@ -41,8 +43,6 @@ __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, unsigned long addr)
 {
 	struct ptdesc *ptdesc = page_ptdesc(pte);
 
-	pagetable_dtor(ptdesc);
-
 #ifndef CONFIG_ARM_LPAE
 	/*
 	 * With the classic ARM MMU, a pte page has two corresponding pmd
@@ -61,7 +61,6 @@ __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