linux-kernel - [PATCH v5 12/17] x86: pgtable: move pagetable_dtor() to __tlb_remove

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Message-Id: <27b3cdc8786bebd4f748380bf82f796482718504.1736317725.git.zhengqi.arch@bytedance.com>
Date: Wed,  8 Jan 2025 14:57:28 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: peterz@...radead.org,
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	Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH v5 12/17] x86: 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.

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: x86@...nel.org
---
 arch/x86/include/asm/tlb.h |  1 +
 arch/x86/kernel/paravirt.c |  1 +
 arch/x86/mm/pgtable.c      | 16 ++++------------
 3 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/tlb.h b/arch/x86/include/asm/tlb.h
index 680ec3d47915a..f64730be5ad67 100644
--- a/arch/x86/include/asm/tlb.h
+++ b/arch/x86/include/asm/tlb.h
@@ -33,6 +33,7 @@ static inline void __tlb_remove_table(void *table)
 {
 	struct ptdesc *ptdesc = (struct ptdesc *)table;
 
+	pagetable_dtor(ptdesc);
 	pagetable_free(ptdesc);
 }
 
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index dc1ab9301d2c6..1ccaa3397a670 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -64,6 +64,7 @@ static void native_tlb_remove_table(struct mmu_gather *tlb, void *table)
 {
 	struct ptdesc *ptdesc = (struct ptdesc *)table;
 
+	pagetable_dtor(ptdesc);
 	tlb_remove_page(tlb, ptdesc_page(ptdesc));
 }
 #else
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index f9516024cbe5d..c02aa0427a6a5 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -25,6 +25,7 @@ void paravirt_tlb_remove_table(struct mmu_gather *tlb, void *table)
 {
 	struct ptdesc *ptdesc = (struct ptdesc *)table;
 
+	pagetable_dtor(ptdesc);
 	tlb_remove_page(tlb, ptdesc_page(ptdesc));
 }
 #else
@@ -62,7 +63,6 @@ early_param("userpte", setup_userpte);
 
 void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
 {
-	pagetable_dtor(page_ptdesc(pte));
 	paravirt_release_pte(page_to_pfn(pte));
 	paravirt_tlb_remove_table(tlb, page_ptdesc(pte));
 }
@@ -70,7 +70,6 @@ void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
 #if CONFIG_PGTABLE_LEVELS > 2
 void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
 {
-	struct ptdesc *ptdesc = virt_to_ptdesc(pmd);
 	paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
 	/*
 	 * NOTE! For PAE, any changes to the top page-directory-pointer-table
@@ -79,28 +78,21 @@ void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
 #ifdef CONFIG_X86_PAE
 	tlb->need_flush_all = 1;
 #endif
-	pagetable_dtor(ptdesc);
-	paravirt_tlb_remove_table(tlb, ptdesc);
+	paravirt_tlb_remove_table(tlb, virt_to_ptdesc(pmd));
 }
 
 #if CONFIG_PGTABLE_LEVELS > 3
 void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
 {
-	struct ptdesc *ptdesc = virt_to_ptdesc(pud);
-
-	pagetable_dtor(ptdesc);
 	paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
-	paravirt_tlb_remove_table(tlb, ptdesc);
+	paravirt_tlb_remove_table(tlb, virt_to_ptdesc(pud));
 }
 
 #if CONFIG_PGTABLE_LEVELS > 4
 void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d)
 {
-	struct ptdesc *ptdesc = virt_to_ptdesc(p4d);
-
-	pagetable_dtor(ptdesc);
 	paravirt_release_p4d(__pa(p4d) >> PAGE_SHIFT);
-	paravirt_tlb_remove_table(tlb, ptdesc);
+	paravirt_tlb_remove_table(tlb, virt_to_ptdesc(p4d));
 }
 #endif	/* CONFIG_PGTABLE_LEVELS > 4 */
 #endif	/* CONFIG_PGTABLE_LEVELS > 3 */
-- 
2.20.1