1df4e817bSPasha Tatashin // SPDX-License-Identifier: GPL-2.0 2df4e817bSPasha Tatashin 3df4e817bSPasha Tatashin /* 4df4e817bSPasha Tatashin * Copyright (c) 2021, Google LLC. 5df4e817bSPasha Tatashin * Pasha Tatashin <pasha.tatashin@soleen.com> 6df4e817bSPasha Tatashin */ 7df4e817bSPasha Tatashin #include <linux/mm.h> 8df4e817bSPasha Tatashin #include <linux/page_table_check.h> 9df4e817bSPasha Tatashin 10df4e817bSPasha Tatashin #undef pr_fmt 11df4e817bSPasha Tatashin #define pr_fmt(fmt) "page_table_check: " fmt 12df4e817bSPasha Tatashin 13df4e817bSPasha Tatashin struct page_table_check { 14df4e817bSPasha Tatashin atomic_t anon_map_count; 15df4e817bSPasha Tatashin atomic_t file_map_count; 16df4e817bSPasha Tatashin }; 17df4e817bSPasha Tatashin 18df4e817bSPasha Tatashin static bool __page_table_check_enabled __initdata = 19df4e817bSPasha Tatashin IS_ENABLED(CONFIG_PAGE_TABLE_CHECK_ENFORCED); 20df4e817bSPasha Tatashin 21df4e817bSPasha Tatashin DEFINE_STATIC_KEY_TRUE(page_table_check_disabled); 22df4e817bSPasha Tatashin EXPORT_SYMBOL(page_table_check_disabled); 23df4e817bSPasha Tatashin 24df4e817bSPasha Tatashin static int __init early_page_table_check_param(char *buf) 25df4e817bSPasha Tatashin { 26597da28eSDr. David Alan Gilbert return strtobool(buf, &__page_table_check_enabled); 27df4e817bSPasha Tatashin } 28df4e817bSPasha Tatashin 29df4e817bSPasha Tatashin early_param("page_table_check", early_page_table_check_param); 30df4e817bSPasha Tatashin 31df4e817bSPasha Tatashin static bool __init need_page_table_check(void) 32df4e817bSPasha Tatashin { 33df4e817bSPasha Tatashin return __page_table_check_enabled; 34df4e817bSPasha Tatashin } 35df4e817bSPasha Tatashin 36df4e817bSPasha Tatashin static void __init init_page_table_check(void) 37df4e817bSPasha Tatashin { 38df4e817bSPasha Tatashin if (!__page_table_check_enabled) 39df4e817bSPasha Tatashin return; 40df4e817bSPasha Tatashin static_branch_disable(&page_table_check_disabled); 41df4e817bSPasha Tatashin } 42df4e817bSPasha Tatashin 43df4e817bSPasha Tatashin struct page_ext_operations page_table_check_ops = { 44df4e817bSPasha Tatashin .size = sizeof(struct page_table_check), 45df4e817bSPasha Tatashin .need = need_page_table_check, 46df4e817bSPasha Tatashin .init = init_page_table_check, 47df4e817bSPasha Tatashin }; 48df4e817bSPasha Tatashin 49df4e817bSPasha Tatashin static struct page_table_check *get_page_table_check(struct page_ext *page_ext) 50df4e817bSPasha Tatashin { 51df4e817bSPasha Tatashin BUG_ON(!page_ext); 52df4e817bSPasha Tatashin return (void *)(page_ext) + page_table_check_ops.offset; 53df4e817bSPasha Tatashin } 54df4e817bSPasha Tatashin 55df4e817bSPasha Tatashin /* 56df4e817bSPasha Tatashin * An enty is removed from the page table, decrement the counters for that page 57df4e817bSPasha Tatashin * verify that it is of correct type and counters do not become negative. 58df4e817bSPasha Tatashin */ 59df4e817bSPasha Tatashin static void page_table_check_clear(struct mm_struct *mm, unsigned long addr, 60df4e817bSPasha Tatashin unsigned long pfn, unsigned long pgcnt) 61df4e817bSPasha Tatashin { 62df4e817bSPasha Tatashin struct page_ext *page_ext; 63df4e817bSPasha Tatashin struct page *page; 6464d8b9e1SPasha Tatashin unsigned long i; 65df4e817bSPasha Tatashin bool anon; 66df4e817bSPasha Tatashin 67df4e817bSPasha Tatashin if (!pfn_valid(pfn)) 68df4e817bSPasha Tatashin return; 69df4e817bSPasha Tatashin 70df4e817bSPasha Tatashin page = pfn_to_page(pfn); 71*b1d5488aSCharan Teja Kalla page_ext = page_ext_get(page); 72df4e817bSPasha Tatashin anon = PageAnon(page); 73df4e817bSPasha Tatashin 74df4e817bSPasha Tatashin for (i = 0; i < pgcnt; i++) { 75df4e817bSPasha Tatashin struct page_table_check *ptc = get_page_table_check(page_ext); 76df4e817bSPasha Tatashin 77df4e817bSPasha Tatashin if (anon) { 78df4e817bSPasha Tatashin BUG_ON(atomic_read(&ptc->file_map_count)); 79df4e817bSPasha Tatashin BUG_ON(atomic_dec_return(&ptc->anon_map_count) < 0); 80df4e817bSPasha Tatashin } else { 81df4e817bSPasha Tatashin BUG_ON(atomic_read(&ptc->anon_map_count)); 82df4e817bSPasha Tatashin BUG_ON(atomic_dec_return(&ptc->file_map_count) < 0); 83df4e817bSPasha Tatashin } 84df4e817bSPasha Tatashin page_ext = page_ext_next(page_ext); 85df4e817bSPasha Tatashin } 86*b1d5488aSCharan Teja Kalla page_ext_put(page_ext); 87df4e817bSPasha Tatashin } 88df4e817bSPasha Tatashin 89df4e817bSPasha Tatashin /* 90df4e817bSPasha Tatashin * A new enty is added to the page table, increment the counters for that page 91df4e817bSPasha Tatashin * verify that it is of correct type and is not being mapped with a different 92df4e817bSPasha Tatashin * type to a different process. 93df4e817bSPasha Tatashin */ 94df4e817bSPasha Tatashin static void page_table_check_set(struct mm_struct *mm, unsigned long addr, 95df4e817bSPasha Tatashin unsigned long pfn, unsigned long pgcnt, 96df4e817bSPasha Tatashin bool rw) 97df4e817bSPasha Tatashin { 98df4e817bSPasha Tatashin struct page_ext *page_ext; 99df4e817bSPasha Tatashin struct page *page; 10064d8b9e1SPasha Tatashin unsigned long i; 101df4e817bSPasha Tatashin bool anon; 102df4e817bSPasha Tatashin 103df4e817bSPasha Tatashin if (!pfn_valid(pfn)) 104df4e817bSPasha Tatashin return; 105df4e817bSPasha Tatashin 106df4e817bSPasha Tatashin page = pfn_to_page(pfn); 107*b1d5488aSCharan Teja Kalla page_ext = page_ext_get(page); 108df4e817bSPasha Tatashin anon = PageAnon(page); 109df4e817bSPasha Tatashin 110df4e817bSPasha Tatashin for (i = 0; i < pgcnt; i++) { 111df4e817bSPasha Tatashin struct page_table_check *ptc = get_page_table_check(page_ext); 112df4e817bSPasha Tatashin 113df4e817bSPasha Tatashin if (anon) { 114df4e817bSPasha Tatashin BUG_ON(atomic_read(&ptc->file_map_count)); 115df4e817bSPasha Tatashin BUG_ON(atomic_inc_return(&ptc->anon_map_count) > 1 && rw); 116df4e817bSPasha Tatashin } else { 117df4e817bSPasha Tatashin BUG_ON(atomic_read(&ptc->anon_map_count)); 118df4e817bSPasha Tatashin BUG_ON(atomic_inc_return(&ptc->file_map_count) < 0); 119df4e817bSPasha Tatashin } 120df4e817bSPasha Tatashin page_ext = page_ext_next(page_ext); 121df4e817bSPasha Tatashin } 122*b1d5488aSCharan Teja Kalla page_ext_put(page_ext); 123df4e817bSPasha Tatashin } 124df4e817bSPasha Tatashin 125df4e817bSPasha Tatashin /* 126df4e817bSPasha Tatashin * page is on free list, or is being allocated, verify that counters are zeroes 127df4e817bSPasha Tatashin * crash if they are not. 128df4e817bSPasha Tatashin */ 129df4e817bSPasha Tatashin void __page_table_check_zero(struct page *page, unsigned int order) 130df4e817bSPasha Tatashin { 131*b1d5488aSCharan Teja Kalla struct page_ext *page_ext; 13264d8b9e1SPasha Tatashin unsigned long i; 133df4e817bSPasha Tatashin 134*b1d5488aSCharan Teja Kalla page_ext = page_ext_get(page); 135df4e817bSPasha Tatashin BUG_ON(!page_ext); 13664d8b9e1SPasha Tatashin for (i = 0; i < (1ul << order); i++) { 137df4e817bSPasha Tatashin struct page_table_check *ptc = get_page_table_check(page_ext); 138df4e817bSPasha Tatashin 139df4e817bSPasha Tatashin BUG_ON(atomic_read(&ptc->anon_map_count)); 140df4e817bSPasha Tatashin BUG_ON(atomic_read(&ptc->file_map_count)); 141df4e817bSPasha Tatashin page_ext = page_ext_next(page_ext); 142df4e817bSPasha Tatashin } 143*b1d5488aSCharan Teja Kalla page_ext_put(page_ext); 144df4e817bSPasha Tatashin } 145df4e817bSPasha Tatashin 146df4e817bSPasha Tatashin void __page_table_check_pte_clear(struct mm_struct *mm, unsigned long addr, 147df4e817bSPasha Tatashin pte_t pte) 148df4e817bSPasha Tatashin { 149df4e817bSPasha Tatashin if (&init_mm == mm) 150df4e817bSPasha Tatashin return; 151df4e817bSPasha Tatashin 152df4e817bSPasha Tatashin if (pte_user_accessible_page(pte)) { 153df4e817bSPasha Tatashin page_table_check_clear(mm, addr, pte_pfn(pte), 154df4e817bSPasha Tatashin PAGE_SIZE >> PAGE_SHIFT); 155df4e817bSPasha Tatashin } 156df4e817bSPasha Tatashin } 157df4e817bSPasha Tatashin EXPORT_SYMBOL(__page_table_check_pte_clear); 158df4e817bSPasha Tatashin 159df4e817bSPasha Tatashin void __page_table_check_pmd_clear(struct mm_struct *mm, unsigned long addr, 160df4e817bSPasha Tatashin pmd_t pmd) 161df4e817bSPasha Tatashin { 162df4e817bSPasha Tatashin if (&init_mm == mm) 163df4e817bSPasha Tatashin return; 164df4e817bSPasha Tatashin 165df4e817bSPasha Tatashin if (pmd_user_accessible_page(pmd)) { 166df4e817bSPasha Tatashin page_table_check_clear(mm, addr, pmd_pfn(pmd), 16792fb0524STong Tiangen PMD_SIZE >> PAGE_SHIFT); 168df4e817bSPasha Tatashin } 169df4e817bSPasha Tatashin } 170df4e817bSPasha Tatashin EXPORT_SYMBOL(__page_table_check_pmd_clear); 171df4e817bSPasha Tatashin 172df4e817bSPasha Tatashin void __page_table_check_pud_clear(struct mm_struct *mm, unsigned long addr, 173df4e817bSPasha Tatashin pud_t pud) 174df4e817bSPasha Tatashin { 175df4e817bSPasha Tatashin if (&init_mm == mm) 176df4e817bSPasha Tatashin return; 177df4e817bSPasha Tatashin 178df4e817bSPasha Tatashin if (pud_user_accessible_page(pud)) { 179df4e817bSPasha Tatashin page_table_check_clear(mm, addr, pud_pfn(pud), 18092fb0524STong Tiangen PUD_SIZE >> PAGE_SHIFT); 181df4e817bSPasha Tatashin } 182df4e817bSPasha Tatashin } 183df4e817bSPasha Tatashin EXPORT_SYMBOL(__page_table_check_pud_clear); 184df4e817bSPasha Tatashin 185df4e817bSPasha Tatashin void __page_table_check_pte_set(struct mm_struct *mm, unsigned long addr, 186df4e817bSPasha Tatashin pte_t *ptep, pte_t pte) 187df4e817bSPasha Tatashin { 188df4e817bSPasha Tatashin if (&init_mm == mm) 189df4e817bSPasha Tatashin return; 190df4e817bSPasha Tatashin 19164d8b9e1SPasha Tatashin __page_table_check_pte_clear(mm, addr, *ptep); 192df4e817bSPasha Tatashin if (pte_user_accessible_page(pte)) { 193df4e817bSPasha Tatashin page_table_check_set(mm, addr, pte_pfn(pte), 194df4e817bSPasha Tatashin PAGE_SIZE >> PAGE_SHIFT, 195df4e817bSPasha Tatashin pte_write(pte)); 196df4e817bSPasha Tatashin } 197df4e817bSPasha Tatashin } 198df4e817bSPasha Tatashin EXPORT_SYMBOL(__page_table_check_pte_set); 199df4e817bSPasha Tatashin 200df4e817bSPasha Tatashin void __page_table_check_pmd_set(struct mm_struct *mm, unsigned long addr, 201df4e817bSPasha Tatashin pmd_t *pmdp, pmd_t pmd) 202df4e817bSPasha Tatashin { 203df4e817bSPasha Tatashin if (&init_mm == mm) 204df4e817bSPasha Tatashin return; 205df4e817bSPasha Tatashin 20664d8b9e1SPasha Tatashin __page_table_check_pmd_clear(mm, addr, *pmdp); 207df4e817bSPasha Tatashin if (pmd_user_accessible_page(pmd)) { 208df4e817bSPasha Tatashin page_table_check_set(mm, addr, pmd_pfn(pmd), 20992fb0524STong Tiangen PMD_SIZE >> PAGE_SHIFT, 210df4e817bSPasha Tatashin pmd_write(pmd)); 211df4e817bSPasha Tatashin } 212df4e817bSPasha Tatashin } 213df4e817bSPasha Tatashin EXPORT_SYMBOL(__page_table_check_pmd_set); 214df4e817bSPasha Tatashin 215df4e817bSPasha Tatashin void __page_table_check_pud_set(struct mm_struct *mm, unsigned long addr, 216df4e817bSPasha Tatashin pud_t *pudp, pud_t pud) 217df4e817bSPasha Tatashin { 218df4e817bSPasha Tatashin if (&init_mm == mm) 219df4e817bSPasha Tatashin return; 220df4e817bSPasha Tatashin 22164d8b9e1SPasha Tatashin __page_table_check_pud_clear(mm, addr, *pudp); 222df4e817bSPasha Tatashin if (pud_user_accessible_page(pud)) { 223df4e817bSPasha Tatashin page_table_check_set(mm, addr, pud_pfn(pud), 22492fb0524STong Tiangen PUD_SIZE >> PAGE_SHIFT, 225df4e817bSPasha Tatashin pud_write(pud)); 226df4e817bSPasha Tatashin } 227df4e817bSPasha Tatashin } 228df4e817bSPasha Tatashin EXPORT_SYMBOL(__page_table_check_pud_set); 22980110bbfSPasha Tatashin 23080110bbfSPasha Tatashin void __page_table_check_pte_clear_range(struct mm_struct *mm, 23180110bbfSPasha Tatashin unsigned long addr, 23280110bbfSPasha Tatashin pmd_t pmd) 23380110bbfSPasha Tatashin { 23480110bbfSPasha Tatashin if (&init_mm == mm) 23580110bbfSPasha Tatashin return; 23680110bbfSPasha Tatashin 23780110bbfSPasha Tatashin if (!pmd_bad(pmd) && !pmd_leaf(pmd)) { 23880110bbfSPasha Tatashin pte_t *ptep = pte_offset_map(&pmd, addr); 23980110bbfSPasha Tatashin unsigned long i; 24080110bbfSPasha Tatashin 24180110bbfSPasha Tatashin for (i = 0; i < PTRS_PER_PTE; i++) { 24280110bbfSPasha Tatashin __page_table_check_pte_clear(mm, addr, *ptep); 24380110bbfSPasha Tatashin addr += PAGE_SIZE; 24480110bbfSPasha Tatashin ptep++; 24580110bbfSPasha Tatashin } 24624c8e27eSMiaohe Lin pte_unmap(ptep - PTRS_PER_PTE); 24780110bbfSPasha Tatashin } 24880110bbfSPasha Tatashin } 249