riscv: 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.

By the way, move the comment above __tlb_remove_table() to
riscv_tlb_remove_ptdesc(), it will be more appropriate.

Link: https://lkml.kernel.org/r/b89d77c965507b1b102cbabe988e69365cb288b6.1736317725.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
index b6793c5c99296e53fef98cd14d43b8e41b8b91b6..c8907b83171153bd7d3fa2a5197f278e9af69b3f 100644 (file)
--- 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 1f6c38420d8e0764d74a27e870f74d055a67f08e..ded8724b3c4f70420e24383ca0603a1067495770 100644 (file)
--- 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 */