[PATCH v4 10/15] riscv: pgtable: move pagetable_dtor() to __tlb_remove_table()
From: Qi Zheng <hidden>
Date: 2024-12-30 09:10:45
Also in:
linux-arch, linux-arm-kernel, linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, linux-um, lkml, loongarch, sparclinux
Subsystem:
mmu gather and tlb invalidation, risc-v architecture, the rest · Maintainers:
Will Deacon, "Aneesh Kumar K.V", Andrew Morton, Nick Piggin, Peter Zijlstra, Paul Walmsley, Palmer Dabbelt, Albert Ou, Linus Torvalds
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. By the way, move the comment above __tlb_remove_table() to riscv_tlb_remove_ptdesc(), it will be more appropriate. Signed-off-by: Qi Zheng <redacted> Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: linux-riscv@lists.infradead.org --- arch/riscv/include/asm/pgalloc.h | 38 ++++++++++++++------------------ arch/riscv/include/asm/tlb.h | 14 ++++-------- 2 files changed, 21 insertions(+), 31 deletions(-)
diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
index b6793c5c99296..c8907b8317115 100644
--- a/arch/riscv/include/asm/pgalloc.h
+++ b/arch/riscv/include/asm/pgalloc.h@@ -15,12 +15,22 @@ #define __HAVE_ARCH_PUD_FREE #include <asm-generic/pgalloc.h> +/* + * While riscv platforms with riscv_ipi_for_rfence as true require an IPI to + * perform TLB shootdown, some platforms with riscv_ipi_for_rfence as false use + * SBI to perform TLB shootdown. To keep software pagetable walkers safe in this + * case we switch to RCU based table free (MMU_GATHER_RCU_TABLE_FREE). See the + * comment below 'ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE' in include/asm-generic/tlb.h + * for more details. + */ static inline void riscv_tlb_remove_ptdesc(struct mmu_gather *tlb, void *pt) { - if (riscv_use_sbi_for_rfence()) + if (riscv_use_sbi_for_rfence()) { tlb_remove_ptdesc(tlb, pt); - else + } else { + pagetable_dtor(pt); tlb_remove_page_ptdesc(tlb, pt); + } } static inline void pmd_populate_kernel(struct mm_struct *mm,
@@ -97,23 +107,15 @@ static inline void pud_free(struct mm_struct *mm, pud_t *pud) static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud, unsigned long addr) { - if (pgtable_l4_enabled) { - struct ptdesc *ptdesc = virt_to_ptdesc(pud); - - pagetable_dtor(ptdesc); - riscv_tlb_remove_ptdesc(tlb, ptdesc); - } + if (pgtable_l4_enabled) + riscv_tlb_remove_ptdesc(tlb, virt_to_ptdesc(pud)); } static inline void __p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d, unsigned long addr) { - if (pgtable_l5_enabled) { - struct ptdesc *ptdesc = virt_to_ptdesc(p4d); - - pagetable_dtor(ptdesc); + if (pgtable_l5_enabled) riscv_tlb_remove_ptdesc(tlb, virt_to_ptdesc(p4d)); - } } #endif /* __PAGETABLE_PMD_FOLDED */
@@ -142,10 +144,7 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm) static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, unsigned long addr) { - struct ptdesc *ptdesc = virt_to_ptdesc(pmd); - - pagetable_dtor(ptdesc); - riscv_tlb_remove_ptdesc(tlb, ptdesc); + riscv_tlb_remove_ptdesc(tlb, virt_to_ptdesc(pmd)); } #endif /* __PAGETABLE_PMD_FOLDED */
@@ -153,10 +152,7 @@ static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, unsigned long addr) { - struct ptdesc *ptdesc = page_ptdesc(pte); - - pagetable_dtor(ptdesc); - riscv_tlb_remove_ptdesc(tlb, ptdesc); + riscv_tlb_remove_ptdesc(tlb, page_ptdesc(pte)); } #endif /* CONFIG_MMU */
diff --git a/arch/riscv/include/asm/tlb.h b/arch/riscv/include/asm/tlb.h
index 1f6c38420d8e0..ded8724b3c4f7 100644
--- a/arch/riscv/include/asm/tlb.h
+++ b/arch/riscv/include/asm/tlb.h@@ -11,19 +11,13 @@ struct mmu_gather; static void tlb_flush(struct mmu_gather *tlb); #ifdef CONFIG_MMU -#include <linux/swap.h> -/* - * While riscv platforms with riscv_ipi_for_rfence as true require an IPI to - * perform TLB shootdown, some platforms with riscv_ipi_for_rfence as false use - * SBI to perform TLB shootdown. To keep software pagetable walkers safe in this - * case we switch to RCU based table free (MMU_GATHER_RCU_TABLE_FREE). See the - * comment below 'ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE' in include/asm-generic/tlb.h - * for more details. - */ static inline void __tlb_remove_table(void *table) { - free_page_and_swap_cache(table); + struct ptdesc *ptdesc = (struct ptdesc *)table; + + pagetable_dtor(ptdesc); + pagetable_free(ptdesc); } #endif /* CONFIG_MMU */
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2.20.1