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 #ifdef CONFIG_MIGRATION 57 } else if (!pte_file(oldpte)) { 58 swp_entry_t entry = pte_to_swp_entry(oldpte); 59 60 if (is_write_migration_entry(entry)) { 61 /* 62 * A protection check is difficult so 63 * just be safe and disable write 64 */ 65 make_migration_entry_read(&entry); 66 set_pte_at(mm, addr, pte, 67 swp_entry_to_pte(entry)); 68 } 69 #endif 70 } 71 72 } while (pte++, addr += PAGE_SIZE, addr != end); 73 arch_leave_lazy_mmu_mode(); 74 pte_unmap_unlock(pte - 1, ptl); 75 } 76 77 static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, 78 unsigned long addr, unsigned long end, pgprot_t newprot, 79 int dirty_accountable) 80 { 81 pmd_t *pmd; 82 unsigned long next; 83 84 pmd = pmd_offset(pud, addr); 85 do { 86 next = pmd_addr_end(addr, end); 87 if (pmd_none_or_clear_bad(pmd)) 88 continue; 89 change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); 90 } while (pmd++, addr = next, addr != end); 91 } 92 93 static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, 94 unsigned long addr, unsigned long end, pgprot_t newprot, 95 int dirty_accountable) 96 { 97 pud_t *pud; 98 unsigned long next; 99 100 pud = pud_offset(pgd, addr); 101 do { 102 next = pud_addr_end(addr, end); 103 if (pud_none_or_clear_bad(pud)) 104 continue; 105 change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); 106 } while (pud++, addr = next, addr != end); 107 } 108 109 static void change_protection(struct vm_area_struct *vma, 110 unsigned long addr, unsigned long end, pgprot_t newprot, 111 int dirty_accountable) 112 { 113 struct mm_struct *mm = vma->vm_mm; 114 pgd_t *pgd; 115 unsigned long next; 116 unsigned long start = addr; 117 118 BUG_ON(addr >= end); 119 pgd = pgd_offset(mm, addr); 120 flush_cache_range(vma, addr, end); 121 do { 122 next = pgd_addr_end(addr, end); 123 if (pgd_none_or_clear_bad(pgd)) 124 continue; 125 change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); 126 } while (pgd++, addr = next, addr != end); 127 flush_tlb_range(vma, start, end); 128 } 129 130 int 131 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, 132 unsigned long start, unsigned long end, unsigned long newflags) 133 { 134 struct mm_struct *mm = vma->vm_mm; 135 unsigned long oldflags = vma->vm_flags; 136 long nrpages = (end - start) >> PAGE_SHIFT; 137 unsigned long charged = 0; 138 pgoff_t pgoff; 139 int error; 140 int dirty_accountable = 0; 141 142 if (newflags == oldflags) { 143 *pprev = vma; 144 return 0; 145 } 146 147 /* 148 * If we make a private mapping writable we increase our commit; 149 * but (without finer accounting) cannot reduce our commit if we 150 * make it unwritable again. 151 * 152 * FIXME? We haven't defined a VM_NORESERVE flag, so mprotecting 153 * a MAP_NORESERVE private mapping to writable will now reserve. 154 */ 155 if (newflags & VM_WRITE) { 156 if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) { 157 charged = nrpages; 158 if (security_vm_enough_memory(charged)) 159 return -ENOMEM; 160 newflags |= VM_ACCOUNT; 161 } 162 } 163 164 /* 165 * First try to merge with previous and/or next vma. 166 */ 167 pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT); 168 *pprev = vma_merge(mm, *pprev, start, end, newflags, 169 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); 170 if (*pprev) { 171 vma = *pprev; 172 goto success; 173 } 174 175 *pprev = vma; 176 177 if (start != vma->vm_start) { 178 error = split_vma(mm, vma, start, 1); 179 if (error) 180 goto fail; 181 } 182 183 if (end != vma->vm_end) { 184 error = split_vma(mm, vma, end, 0); 185 if (error) 186 goto fail; 187 } 188 189 success: 190 /* 191 * vm_flags and vm_page_prot are protected by the mmap_sem 192 * held in write mode. 193 */ 194 vma->vm_flags = newflags; 195 vma->vm_page_prot = vm_get_page_prot(newflags); 196 if (vma_wants_writenotify(vma)) { 197 vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED); 198 dirty_accountable = 1; 199 } 200 201 if (is_vm_hugetlb_page(vma)) 202 hugetlb_change_protection(vma, start, end, vma->vm_page_prot); 203 else 204 change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); 205 vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); 206 vm_stat_account(mm, newflags, vma->vm_file, nrpages); 207 return 0; 208 209 fail: 210 vm_unacct_memory(charged); 211 return error; 212 } 213 214 asmlinkage long 215 sys_mprotect(unsigned long start, size_t len, unsigned long prot) 216 { 217 unsigned long vm_flags, nstart, end, tmp, reqprot; 218 struct vm_area_struct *vma, *prev; 219 int error = -EINVAL; 220 const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP); 221 prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP); 222 if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */ 223 return -EINVAL; 224 225 if (start & ~PAGE_MASK) 226 return -EINVAL; 227 if (!len) 228 return 0; 229 len = PAGE_ALIGN(len); 230 end = start + len; 231 if (end <= start) 232 return -ENOMEM; 233 if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) 234 return -EINVAL; 235 236 reqprot = prot; 237 /* 238 * Does the application expect PROT_READ to imply PROT_EXEC: 239 */ 240 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 241 prot |= PROT_EXEC; 242 243 vm_flags = calc_vm_prot_bits(prot); 244 245 down_write(¤t->mm->mmap_sem); 246 247 vma = find_vma_prev(current->mm, start, &prev); 248 error = -ENOMEM; 249 if (!vma) 250 goto out; 251 if (unlikely(grows & PROT_GROWSDOWN)) { 252 if (vma->vm_start >= end) 253 goto out; 254 start = vma->vm_start; 255 error = -EINVAL; 256 if (!(vma->vm_flags & VM_GROWSDOWN)) 257 goto out; 258 } 259 else { 260 if (vma->vm_start > start) 261 goto out; 262 if (unlikely(grows & PROT_GROWSUP)) { 263 end = vma->vm_end; 264 error = -EINVAL; 265 if (!(vma->vm_flags & VM_GROWSUP)) 266 goto out; 267 } 268 } 269 if (start > vma->vm_start) 270 prev = vma; 271 272 for (nstart = start ; ; ) { 273 unsigned long newflags; 274 275 /* Here we know that vma->vm_start <= nstart < vma->vm_end. */ 276 277 newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC)); 278 279 /* newflags >> 4 shift VM_MAY% in place of VM_% */ 280 if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) { 281 error = -EACCES; 282 goto out; 283 } 284 285 error = security_file_mprotect(vma, reqprot, prot); 286 if (error) 287 goto out; 288 289 tmp = vma->vm_end; 290 if (tmp > end) 291 tmp = end; 292 error = mprotect_fixup(vma, &prev, nstart, tmp, newflags); 293 if (error) 294 goto out; 295 nstart = tmp; 296 297 if (nstart < prev->vm_end) 298 nstart = prev->vm_end; 299 if (nstart >= end) 300 goto out; 301 302 vma = prev->vm_next; 303 if (!vma || vma->vm_start != nstart) { 304 error = -ENOMEM; 305 goto out; 306 } 307 } 308 out: 309 up_write(¤t->mm->mmap_sem); 310 return error; 311 } 312