1 /* 2 * mm/mprotect.c 3 * 4 * (C) Copyright 1994 Linus Torvalds 5 * (C) Copyright 2002 Christoph Hellwig 6 * 7 * Address space accounting code <alan@redhat.com> 8 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved 9 */ 10 11 #include <linux/mm.h> 12 #include <linux/hugetlb.h> 13 #include <linux/slab.h> 14 #include <linux/shm.h> 15 #include <linux/mman.h> 16 #include <linux/fs.h> 17 #include <linux/highmem.h> 18 #include <linux/security.h> 19 #include <linux/mempolicy.h> 20 #include <linux/personality.h> 21 #include <linux/syscalls.h> 22 #include <linux/swap.h> 23 #include <linux/swapops.h> 24 #include <asm/uaccess.h> 25 #include <asm/pgtable.h> 26 #include <asm/cacheflush.h> 27 #include <asm/tlbflush.h> 28 29 static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, 30 unsigned long addr, unsigned long end, pgprot_t newprot, 31 int dirty_accountable) 32 { 33 pte_t *pte, oldpte; 34 spinlock_t *ptl; 35 36 pte = pte_offset_map_lock(mm, pmd, addr, &ptl); 37 arch_enter_lazy_mmu_mode(); 38 do { 39 oldpte = *pte; 40 if (pte_present(oldpte)) { 41 pte_t ptent; 42 43 /* Avoid an SMP race with hardware updated dirty/clean 44 * bits by wiping the pte and then setting the new pte 45 * into place. 46 */ 47 ptent = ptep_get_and_clear(mm, addr, pte); 48 ptent = pte_modify(ptent, newprot); 49 /* 50 * Avoid taking write faults for pages we know to be 51 * dirty. 52 */ 53 if (dirty_accountable && pte_dirty(ptent)) 54 ptent = pte_mkwrite(ptent); 55 set_pte_at(mm, addr, pte, ptent); 56 lazy_mmu_prot_update(ptent); 57 #ifdef CONFIG_MIGRATION 58 } else if (!pte_file(oldpte)) { 59 swp_entry_t entry = pte_to_swp_entry(oldpte); 60 61 if (is_write_migration_entry(entry)) { 62 /* 63 * A protection check is difficult so 64 * just be safe and disable write 65 */ 66 make_migration_entry_read(&entry); 67 set_pte_at(mm, addr, pte, 68 swp_entry_to_pte(entry)); 69 } 70 #endif 71 } 72 73 } while (pte++, addr += PAGE_SIZE, addr != end); 74 arch_leave_lazy_mmu_mode(); 75 pte_unmap_unlock(pte - 1, ptl); 76 } 77 78 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, 79 unsigned long addr, unsigned long end, pgprot_t newprot, 80 int dirty_accountable) 81 { 82 pmd_t *pmd; 83 unsigned long next; 84 85 pmd = pmd_offset(pud, addr); 86 do { 87 next = pmd_addr_end(addr, end); 88 if (pmd_none_or_clear_bad(pmd)) 89 continue; 90 change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); 91 } while (pmd++, addr = next, addr != end); 92 } 93 94 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, 95 unsigned long addr, unsigned long end, pgprot_t newprot, 96 int dirty_accountable) 97 { 98 pud_t *pud; 99 unsigned long next; 100 101 pud = pud_offset(pgd, addr); 102 do { 103 next = pud_addr_end(addr, end); 104 if (pud_none_or_clear_bad(pud)) 105 continue; 106 change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); 107 } while (pud++, addr = next, addr != end); 108 } 109 110 static void change_protection(struct vm_area_struct *vma, 111 unsigned long addr, unsigned long end, pgprot_t newprot, 112 int dirty_accountable) 113 { 114 struct mm_struct *mm = vma->vm_mm; 115 pgd_t *pgd; 116 unsigned long next; 117 unsigned long start = addr; 118 119 BUG_ON(addr >= end); 120 pgd = pgd_offset(mm, addr); 121 flush_cache_range(vma, addr, end); 122 do { 123 next = pgd_addr_end(addr, end); 124 if (pgd_none_or_clear_bad(pgd)) 125 continue; 126 change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); 127 } while (pgd++, addr = next, addr != end); 128 flush_tlb_range(vma, start, end); 129 } 130 131 static int 132 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 133 unsigned long start, unsigned long end, unsigned long newflags) 134 { 135 struct mm_struct *mm = vma->vm_mm; 136 unsigned long oldflags = vma->vm_flags; 137 long nrpages = (end - start) >> PAGE_SHIFT; 138 unsigned long charged = 0; 139 pgoff_t pgoff; 140 int error; 141 int dirty_accountable = 0; 142 143 if (newflags == oldflags) { 144 *pprev = vma; 145 return 0; 146 } 147 148 /* 149 * If we make a private mapping writable we increase our commit; 150 * but (without finer accounting) cannot reduce our commit if we 151 * make it unwritable again. 152 * 153 * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting 154 * a MAP_NORESERVE private mapping to writable will now reserve. 155 */ 156 if (newflags & VM_WRITE) { 157 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) { 158 charged = nrpages; 159 if (security_vm_enough_memory(charged)) 160 return -ENOMEM; 161 newflags |= VM_ACCOUNT; 162 } 163 } 164 165 /* 166 * First try to merge with previous and/or next vma. 167 */ 168 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); 169 *pprev = vma_merge(mm, *pprev, start, end, newflags, 170 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); 171 if (*pprev) { 172 vma = *pprev; 173 goto success; 174 } 175 176 *pprev = vma; 177 178 if (start != vma->vm_start) { 179 error = split_vma(mm, vma, start, 1); 180 if (error) 181 goto fail; 182 } 183 184 if (end != vma->vm_end) { 185 error = split_vma(mm, vma, end, 0); 186 if (error) 187 goto fail; 188 } 189 190 success: 191 /* 192 * vm_flags and vm_page_prot are protected by the mmap_sem 193 * held in write mode. 194 */ 195 vma->vm_flags = newflags; 196 vma->vm_page_prot = protection_map[newflags & 197 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]; 198 if (vma_wants_writenotify(vma)) { 199 vma->vm_page_prot = protection_map[newflags & 200 (VM_READ|VM_WRITE|VM_EXEC)]; 201 dirty_accountable = 1; 202 } 203 204 if (is_vm_hugetlb_page(vma)) 205 hugetlb_change_protection(vma, start, end, vma->vm_page_prot); 206 else 207 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); 208 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); 209 vm_stat_account(mm, newflags, vma->vm_file, nrpages); 210 return 0; 211 212 fail: 213 vm_unacct_memory(charged); 214 return error; 215 } 216 217 asmlinkage long 218 sys_mprotect(unsigned long start, size_t len, unsigned long prot) 219 { 220 unsigned long vm_flags, nstart, end, tmp, reqprot; 221 struct vm_area_struct *vma, *prev; 222 int error = -EINVAL; 223 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 224 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 225 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 226 return -EINVAL; 227 228 if (start & ~PAGE_MASK) 229 return -EINVAL; 230 if (!len) 231 return 0; 232 len = PAGE_ALIGN(len); 233 end = start + len; 234 if (end <= start) 235 return -ENOMEM; 236 if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) 237 return -EINVAL; 238 239 reqprot = prot; 240 /* 241 * Does the application expect PROT_READ to imply PROT_EXEC: 242 */ 243 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 244 prot |= PROT_EXEC; 245 246 vm_flags = calc_vm_prot_bits(prot); 247 248 down_write(¤t->mm->mmap_sem); 249 250 vma = find_vma_prev(current->mm, start, &prev); 251 error = -ENOMEM; 252 if (!vma) 253 goto out; 254 if (unlikely(grows & PROT_GROWSDOWN)) { 255 if (vma->vm_start >= end) 256 goto out; 257 start = vma->vm_start; 258 error = -EINVAL; 259 if (!(vma->vm_flags & VM_GROWSDOWN)) 260 goto out; 261 } 262 else { 263 if (vma->vm_start > start) 264 goto out; 265 if (unlikely(grows & PROT_GROWSUP)) { 266 end = vma->vm_end; 267 error = -EINVAL; 268 if (!(vma->vm_flags & VM_GROWSUP)) 269 goto out; 270 } 271 } 272 if (start > vma->vm_start) 273 prev = vma; 274 275 for (nstart = start ; ; ) { 276 unsigned long newflags; 277 278 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ 279 280 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); 281 282 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 283 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { 284 error = -EACCES; 285 goto out; 286 } 287 288 error = security_file_mprotect(vma, reqprot, prot); 289 if (error) 290 goto out; 291 292 tmp = vma->vm_end; 293 if (tmp > end) 294 tmp = end; 295 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); 296 if (error) 297 goto out; 298 nstart = tmp; 299 300 if (nstart < prev->vm_end) 301 nstart = prev->vm_end; 302 if (nstart >= end) 303 goto out; 304 305 vma = prev->vm_next; 306 if (!vma || vma->vm_start != nstart) { 307 error = -ENOMEM; 308 goto out; 309 } 310 } 311 out: 312 up_write(¤t->mm->mmap_sem); 313 return error; 314 } 315