1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * mm/mmap.c 4 * 5 * Written by obz. 6 * 7 * Address space accounting code <alan@lxorguk.ukuu.org.uk> 8 */ 9 10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 11 12 #include <linux/kernel.h> 13 #include <linux/slab.h> 14 #include <linux/backing-dev.h> 15 #include <linux/mm.h> 16 #include <linux/mm_inline.h> 17 #include <linux/shm.h> 18 #include <linux/mman.h> 19 #include <linux/pagemap.h> 20 #include <linux/swap.h> 21 #include <linux/syscalls.h> 22 #include <linux/capability.h> 23 #include <linux/init.h> 24 #include <linux/file.h> 25 #include <linux/fs.h> 26 #include <linux/personality.h> 27 #include <linux/security.h> 28 #include <linux/hugetlb.h> 29 #include <linux/shmem_fs.h> 30 #include <linux/profile.h> 31 #include <linux/export.h> 32 #include <linux/mount.h> 33 #include <linux/mempolicy.h> 34 #include <linux/rmap.h> 35 #include <linux/mmu_notifier.h> 36 #include <linux/mmdebug.h> 37 #include <linux/perf_event.h> 38 #include <linux/audit.h> 39 #include <linux/khugepaged.h> 40 #include <linux/uprobes.h> 41 #include <linux/notifier.h> 42 #include <linux/memory.h> 43 #include <linux/printk.h> 44 #include <linux/userfaultfd_k.h> 45 #include <linux/moduleparam.h> 46 #include <linux/pkeys.h> 47 #include <linux/oom.h> 48 #include <linux/sched/mm.h> 49 #include <linux/ksm.h> 50 #include <linux/memfd.h> 51 52 #include <linux/uaccess.h> 53 #include <asm/cacheflush.h> 54 #include <asm/tlb.h> 55 #include <asm/mmu_context.h> 56 57 #define CREATE_TRACE_POINTS 58 #include <trace/events/mmap.h> 59 60 #include "internal.h" 61 62 #ifndef arch_mmap_check 63 #define arch_mmap_check(addr, len, flags) (0) 64 #endif 65 66 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS 67 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN; 68 int mmap_rnd_bits_max __ro_after_init = CONFIG_ARCH_MMAP_RND_BITS_MAX; 69 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS; 70 #endif 71 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS 72 const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN; 73 const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX; 74 int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS; 75 #endif 76 77 static bool ignore_rlimit_data; 78 core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644); 79 80 /* Update vma->vm_page_prot to reflect vma->vm_flags. */ 81 void vma_set_page_prot(struct vm_area_struct *vma) 82 { 83 unsigned long vm_flags = vma->vm_flags; 84 pgprot_t vm_page_prot; 85 86 vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags); 87 if (vma_wants_writenotify(vma, vm_page_prot)) { 88 vm_flags &= ~VM_SHARED; 89 vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags); 90 } 91 /* remove_protection_ptes reads vma->vm_page_prot without mmap_lock */ 92 WRITE_ONCE(vma->vm_page_prot, vm_page_prot); 93 } 94 95 /* 96 * check_brk_limits() - Use platform specific check of range & verify mlock 97 * limits. 98 * @addr: The address to check 99 * @len: The size of increase. 100 * 101 * Return: 0 on success. 102 */ 103 static int check_brk_limits(unsigned long addr, unsigned long len) 104 { 105 unsigned long mapped_addr; 106 107 mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); 108 if (IS_ERR_VALUE(mapped_addr)) 109 return mapped_addr; 110 111 return mlock_future_ok(current->mm, current->mm->def_flags, len) 112 ? 0 : -EAGAIN; 113 } 114 static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *brkvma, 115 unsigned long addr, unsigned long request, unsigned long flags); 116 SYSCALL_DEFINE1(brk, unsigned long, brk) 117 { 118 unsigned long newbrk, oldbrk, origbrk; 119 struct mm_struct *mm = current->mm; 120 struct vm_area_struct *brkvma, *next = NULL; 121 unsigned long min_brk; 122 bool populate = false; 123 LIST_HEAD(uf); 124 struct vma_iterator vmi; 125 126 if (mmap_write_lock_killable(mm)) 127 return -EINTR; 128 129 origbrk = mm->brk; 130 131 #ifdef CONFIG_COMPAT_BRK 132 /* 133 * CONFIG_COMPAT_BRK can still be overridden by setting 134 * randomize_va_space to 2, which will still cause mm->start_brk 135 * to be arbitrarily shifted 136 */ 137 if (current->brk_randomized) 138 min_brk = mm->start_brk; 139 else 140 min_brk = mm->end_data; 141 #else 142 min_brk = mm->start_brk; 143 #endif 144 if (brk < min_brk) 145 goto out; 146 147 /* 148 * Check against rlimit here. If this check is done later after the test 149 * of oldbrk with newbrk then it can escape the test and let the data 150 * segment grow beyond its set limit the in case where the limit is 151 * not page aligned -Ram Gupta 152 */ 153 if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk, 154 mm->end_data, mm->start_data)) 155 goto out; 156 157 newbrk = PAGE_ALIGN(brk); 158 oldbrk = PAGE_ALIGN(mm->brk); 159 if (oldbrk == newbrk) { 160 mm->brk = brk; 161 goto success; 162 } 163 164 /* Always allow shrinking brk. */ 165 if (brk <= mm->brk) { 166 /* Search one past newbrk */ 167 vma_iter_init(&vmi, mm, newbrk); 168 brkvma = vma_find(&vmi, oldbrk); 169 if (!brkvma || brkvma->vm_start >= oldbrk) 170 goto out; /* mapping intersects with an existing non-brk vma. */ 171 /* 172 * mm->brk must be protected by write mmap_lock. 173 * do_vmi_align_munmap() will drop the lock on success, so 174 * update it before calling do_vma_munmap(). 175 */ 176 mm->brk = brk; 177 if (do_vmi_align_munmap(&vmi, brkvma, mm, newbrk, oldbrk, &uf, 178 /* unlock = */ true)) 179 goto out; 180 181 goto success_unlocked; 182 } 183 184 if (check_brk_limits(oldbrk, newbrk - oldbrk)) 185 goto out; 186 187 /* 188 * Only check if the next VMA is within the stack_guard_gap of the 189 * expansion area 190 */ 191 vma_iter_init(&vmi, mm, oldbrk); 192 next = vma_find(&vmi, newbrk + PAGE_SIZE + stack_guard_gap); 193 if (next && newbrk + PAGE_SIZE > vm_start_gap(next)) 194 goto out; 195 196 brkvma = vma_prev_limit(&vmi, mm->start_brk); 197 /* Ok, looks good - let it rip. */ 198 if (do_brk_flags(&vmi, brkvma, oldbrk, newbrk - oldbrk, 0) < 0) 199 goto out; 200 201 mm->brk = brk; 202 if (mm->def_flags & VM_LOCKED) 203 populate = true; 204 205 success: 206 mmap_write_unlock(mm); 207 success_unlocked: 208 userfaultfd_unmap_complete(mm, &uf); 209 if (populate) 210 mm_populate(oldbrk, newbrk - oldbrk); 211 return brk; 212 213 out: 214 mm->brk = origbrk; 215 mmap_write_unlock(mm); 216 return origbrk; 217 } 218 219 /* 220 * If a hint addr is less than mmap_min_addr change hint to be as 221 * low as possible but still greater than mmap_min_addr 222 */ 223 static inline unsigned long round_hint_to_min(unsigned long hint) 224 { 225 hint &= PAGE_MASK; 226 if (((void *)hint != NULL) && 227 (hint < mmap_min_addr)) 228 return PAGE_ALIGN(mmap_min_addr); 229 return hint; 230 } 231 232 bool mlock_future_ok(struct mm_struct *mm, unsigned long flags, 233 unsigned long bytes) 234 { 235 unsigned long locked_pages, limit_pages; 236 237 if (!(flags & VM_LOCKED) || capable(CAP_IPC_LOCK)) 238 return true; 239 240 locked_pages = bytes >> PAGE_SHIFT; 241 locked_pages += mm->locked_vm; 242 243 limit_pages = rlimit(RLIMIT_MEMLOCK); 244 limit_pages >>= PAGE_SHIFT; 245 246 return locked_pages <= limit_pages; 247 } 248 249 static inline u64 file_mmap_size_max(struct file *file, struct inode *inode) 250 { 251 if (S_ISREG(inode->i_mode)) 252 return MAX_LFS_FILESIZE; 253 254 if (S_ISBLK(inode->i_mode)) 255 return MAX_LFS_FILESIZE; 256 257 if (S_ISSOCK(inode->i_mode)) 258 return MAX_LFS_FILESIZE; 259 260 /* Special "we do even unsigned file positions" case */ 261 if (file->f_op->fop_flags & FOP_UNSIGNED_OFFSET) 262 return 0; 263 264 /* Yes, random drivers might want more. But I'm tired of buggy drivers */ 265 return ULONG_MAX; 266 } 267 268 static inline bool file_mmap_ok(struct file *file, struct inode *inode, 269 unsigned long pgoff, unsigned long len) 270 { 271 u64 maxsize = file_mmap_size_max(file, inode); 272 273 if (maxsize && len > maxsize) 274 return false; 275 maxsize -= len; 276 if (pgoff > maxsize >> PAGE_SHIFT) 277 return false; 278 return true; 279 } 280 281 /* 282 * The caller must write-lock current->mm->mmap_lock. 283 */ 284 unsigned long do_mmap(struct file *file, unsigned long addr, 285 unsigned long len, unsigned long prot, 286 unsigned long flags, vm_flags_t vm_flags, 287 unsigned long pgoff, unsigned long *populate, 288 struct list_head *uf) 289 { 290 struct mm_struct *mm = current->mm; 291 int pkey = 0; 292 293 *populate = 0; 294 295 if (!len) 296 return -EINVAL; 297 298 /* 299 * Does the application expect PROT_READ to imply PROT_EXEC? 300 * 301 * (the exception is when the underlying filesystem is noexec 302 * mounted, in which case we don't add PROT_EXEC.) 303 */ 304 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 305 if (!(file && path_noexec(&file->f_path))) 306 prot |= PROT_EXEC; 307 308 /* force arch specific MAP_FIXED handling in get_unmapped_area */ 309 if (flags & MAP_FIXED_NOREPLACE) 310 flags |= MAP_FIXED; 311 312 if (!(flags & MAP_FIXED)) 313 addr = round_hint_to_min(addr); 314 315 /* Careful about overflows.. */ 316 len = PAGE_ALIGN(len); 317 if (!len) 318 return -ENOMEM; 319 320 /* offset overflow? */ 321 if ((pgoff + (len >> PAGE_SHIFT)) < pgoff) 322 return -EOVERFLOW; 323 324 /* Too many mappings? */ 325 if (mm->map_count > sysctl_max_map_count) 326 return -ENOMEM; 327 328 /* 329 * addr is returned from get_unmapped_area, 330 * There are two cases: 331 * 1> MAP_FIXED == false 332 * unallocated memory, no need to check sealing. 333 * 1> MAP_FIXED == true 334 * sealing is checked inside mmap_region when 335 * do_vmi_munmap is called. 336 */ 337 338 if (prot == PROT_EXEC) { 339 pkey = execute_only_pkey(mm); 340 if (pkey < 0) 341 pkey = 0; 342 } 343 344 /* Do simple checking here so the lower-level routines won't have 345 * to. we assume access permissions have been handled by the open 346 * of the memory object, so we don't do any here. 347 */ 348 vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(file, flags) | 349 mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; 350 351 /* Obtain the address to map to. we verify (or select) it and ensure 352 * that it represents a valid section of the address space. 353 */ 354 addr = __get_unmapped_area(file, addr, len, pgoff, flags, vm_flags); 355 if (IS_ERR_VALUE(addr)) 356 return addr; 357 358 if (flags & MAP_FIXED_NOREPLACE) { 359 if (find_vma_intersection(mm, addr, addr + len)) 360 return -EEXIST; 361 } 362 363 if (flags & MAP_LOCKED) 364 if (!can_do_mlock()) 365 return -EPERM; 366 367 if (!mlock_future_ok(mm, vm_flags, len)) 368 return -EAGAIN; 369 370 if (file) { 371 struct inode *inode = file_inode(file); 372 unsigned int seals = memfd_file_seals(file); 373 unsigned long flags_mask; 374 375 if (!file_mmap_ok(file, inode, pgoff, len)) 376 return -EOVERFLOW; 377 378 flags_mask = LEGACY_MAP_MASK; 379 if (file->f_op->fop_flags & FOP_MMAP_SYNC) 380 flags_mask |= MAP_SYNC; 381 382 switch (flags & MAP_TYPE) { 383 case MAP_SHARED: 384 /* 385 * Force use of MAP_SHARED_VALIDATE with non-legacy 386 * flags. E.g. MAP_SYNC is dangerous to use with 387 * MAP_SHARED as you don't know which consistency model 388 * you will get. We silently ignore unsupported flags 389 * with MAP_SHARED to preserve backward compatibility. 390 */ 391 flags &= LEGACY_MAP_MASK; 392 fallthrough; 393 case MAP_SHARED_VALIDATE: 394 if (flags & ~flags_mask) 395 return -EOPNOTSUPP; 396 if (prot & PROT_WRITE) { 397 if (!(file->f_mode & FMODE_WRITE)) 398 return -EACCES; 399 if (IS_SWAPFILE(file->f_mapping->host)) 400 return -ETXTBSY; 401 } 402 403 /* 404 * Make sure we don't allow writing to an append-only 405 * file.. 406 */ 407 if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE)) 408 return -EACCES; 409 410 vm_flags |= VM_SHARED | VM_MAYSHARE; 411 if (!(file->f_mode & FMODE_WRITE)) 412 vm_flags &= ~(VM_MAYWRITE | VM_SHARED); 413 else if (is_readonly_sealed(seals, vm_flags)) 414 vm_flags &= ~VM_MAYWRITE; 415 fallthrough; 416 case MAP_PRIVATE: 417 if (!(file->f_mode & FMODE_READ)) 418 return -EACCES; 419 if (path_noexec(&file->f_path)) { 420 if (vm_flags & VM_EXEC) 421 return -EPERM; 422 vm_flags &= ~VM_MAYEXEC; 423 } 424 425 if (!file->f_op->mmap) 426 return -ENODEV; 427 if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) 428 return -EINVAL; 429 break; 430 431 default: 432 return -EINVAL; 433 } 434 } else { 435 switch (flags & MAP_TYPE) { 436 case MAP_SHARED: 437 if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) 438 return -EINVAL; 439 /* 440 * Ignore pgoff. 441 */ 442 pgoff = 0; 443 vm_flags |= VM_SHARED | VM_MAYSHARE; 444 break; 445 case MAP_DROPPABLE: 446 if (VM_DROPPABLE == VM_NONE) 447 return -ENOTSUPP; 448 /* 449 * A locked or stack area makes no sense to be droppable. 450 * 451 * Also, since droppable pages can just go away at any time 452 * it makes no sense to copy them on fork or dump them. 453 * 454 * And don't attempt to combine with hugetlb for now. 455 */ 456 if (flags & (MAP_LOCKED | MAP_HUGETLB)) 457 return -EINVAL; 458 if (vm_flags & (VM_GROWSDOWN | VM_GROWSUP)) 459 return -EINVAL; 460 461 vm_flags |= VM_DROPPABLE; 462 463 /* 464 * If the pages can be dropped, then it doesn't make 465 * sense to reserve them. 466 */ 467 vm_flags |= VM_NORESERVE; 468 469 /* 470 * Likewise, they're volatile enough that they 471 * shouldn't survive forks or coredumps. 472 */ 473 vm_flags |= VM_WIPEONFORK | VM_DONTDUMP; 474 fallthrough; 475 case MAP_PRIVATE: 476 /* 477 * Set pgoff according to addr for anon_vma. 478 */ 479 pgoff = addr >> PAGE_SHIFT; 480 break; 481 default: 482 return -EINVAL; 483 } 484 } 485 486 /* 487 * Set 'VM_NORESERVE' if we should not account for the 488 * memory use of this mapping. 489 */ 490 if (flags & MAP_NORESERVE) { 491 /* We honor MAP_NORESERVE if allowed to overcommit */ 492 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER) 493 vm_flags |= VM_NORESERVE; 494 495 /* hugetlb applies strict overcommit unless MAP_NORESERVE */ 496 if (file && is_file_hugepages(file)) 497 vm_flags |= VM_NORESERVE; 498 } 499 500 addr = mmap_region(file, addr, len, vm_flags, pgoff, uf); 501 if (!IS_ERR_VALUE(addr) && 502 ((vm_flags & VM_LOCKED) || 503 (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE)) 504 *populate = len; 505 return addr; 506 } 507 508 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len, 509 unsigned long prot, unsigned long flags, 510 unsigned long fd, unsigned long pgoff) 511 { 512 struct file *file = NULL; 513 unsigned long retval; 514 515 if (!(flags & MAP_ANONYMOUS)) { 516 audit_mmap_fd(fd, flags); 517 file = fget(fd); 518 if (!file) 519 return -EBADF; 520 if (is_file_hugepages(file)) { 521 len = ALIGN(len, huge_page_size(hstate_file(file))); 522 } else if (unlikely(flags & MAP_HUGETLB)) { 523 retval = -EINVAL; 524 goto out_fput; 525 } 526 } else if (flags & MAP_HUGETLB) { 527 struct hstate *hs; 528 529 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK); 530 if (!hs) 531 return -EINVAL; 532 533 len = ALIGN(len, huge_page_size(hs)); 534 /* 535 * VM_NORESERVE is used because the reservations will be 536 * taken when vm_ops->mmap() is called 537 */ 538 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, 539 VM_NORESERVE, 540 HUGETLB_ANONHUGE_INODE, 541 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK); 542 if (IS_ERR(file)) 543 return PTR_ERR(file); 544 } 545 546 retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff); 547 out_fput: 548 if (file) 549 fput(file); 550 return retval; 551 } 552 553 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len, 554 unsigned long, prot, unsigned long, flags, 555 unsigned long, fd, unsigned long, pgoff) 556 { 557 return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff); 558 } 559 560 #ifdef __ARCH_WANT_SYS_OLD_MMAP 561 struct mmap_arg_struct { 562 unsigned long addr; 563 unsigned long len; 564 unsigned long prot; 565 unsigned long flags; 566 unsigned long fd; 567 unsigned long offset; 568 }; 569 570 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) 571 { 572 struct mmap_arg_struct a; 573 574 if (copy_from_user(&a, arg, sizeof(a))) 575 return -EFAULT; 576 if (offset_in_page(a.offset)) 577 return -EINVAL; 578 579 return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, 580 a.offset >> PAGE_SHIFT); 581 } 582 #endif /* __ARCH_WANT_SYS_OLD_MMAP */ 583 584 /** 585 * unmapped_area() - Find an area between the low_limit and the high_limit with 586 * the correct alignment and offset, all from @info. Note: current->mm is used 587 * for the search. 588 * 589 * @info: The unmapped area information including the range [low_limit - 590 * high_limit), the alignment offset and mask. 591 * 592 * Return: A memory address or -ENOMEM. 593 */ 594 static unsigned long unmapped_area(struct vm_unmapped_area_info *info) 595 { 596 unsigned long length, gap; 597 unsigned long low_limit, high_limit; 598 struct vm_area_struct *tmp; 599 VMA_ITERATOR(vmi, current->mm, 0); 600 601 /* Adjust search length to account for worst case alignment overhead */ 602 length = info->length + info->align_mask + info->start_gap; 603 if (length < info->length) 604 return -ENOMEM; 605 606 low_limit = info->low_limit; 607 if (low_limit < mmap_min_addr) 608 low_limit = mmap_min_addr; 609 high_limit = info->high_limit; 610 retry: 611 if (vma_iter_area_lowest(&vmi, low_limit, high_limit, length)) 612 return -ENOMEM; 613 614 /* 615 * Adjust for the gap first so it doesn't interfere with the 616 * later alignment. The first step is the minimum needed to 617 * fulill the start gap, the next steps is the minimum to align 618 * that. It is the minimum needed to fulill both. 619 */ 620 gap = vma_iter_addr(&vmi) + info->start_gap; 621 gap += (info->align_offset - gap) & info->align_mask; 622 tmp = vma_next(&vmi); 623 if (tmp && (tmp->vm_flags & VM_STARTGAP_FLAGS)) { /* Avoid prev check if possible */ 624 if (vm_start_gap(tmp) < gap + length - 1) { 625 low_limit = tmp->vm_end; 626 vma_iter_reset(&vmi); 627 goto retry; 628 } 629 } else { 630 tmp = vma_prev(&vmi); 631 if (tmp && vm_end_gap(tmp) > gap) { 632 low_limit = vm_end_gap(tmp); 633 vma_iter_reset(&vmi); 634 goto retry; 635 } 636 } 637 638 return gap; 639 } 640 641 /** 642 * unmapped_area_topdown() - Find an area between the low_limit and the 643 * high_limit with the correct alignment and offset at the highest available 644 * address, all from @info. Note: current->mm is used for the search. 645 * 646 * @info: The unmapped area information including the range [low_limit - 647 * high_limit), the alignment offset and mask. 648 * 649 * Return: A memory address or -ENOMEM. 650 */ 651 static unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info) 652 { 653 unsigned long length, gap, gap_end; 654 unsigned long low_limit, high_limit; 655 struct vm_area_struct *tmp; 656 VMA_ITERATOR(vmi, current->mm, 0); 657 658 /* Adjust search length to account for worst case alignment overhead */ 659 length = info->length + info->align_mask + info->start_gap; 660 if (length < info->length) 661 return -ENOMEM; 662 663 low_limit = info->low_limit; 664 if (low_limit < mmap_min_addr) 665 low_limit = mmap_min_addr; 666 high_limit = info->high_limit; 667 retry: 668 if (vma_iter_area_highest(&vmi, low_limit, high_limit, length)) 669 return -ENOMEM; 670 671 gap = vma_iter_end(&vmi) - info->length; 672 gap -= (gap - info->align_offset) & info->align_mask; 673 gap_end = vma_iter_end(&vmi); 674 tmp = vma_next(&vmi); 675 if (tmp && (tmp->vm_flags & VM_STARTGAP_FLAGS)) { /* Avoid prev check if possible */ 676 if (vm_start_gap(tmp) < gap_end) { 677 high_limit = vm_start_gap(tmp); 678 vma_iter_reset(&vmi); 679 goto retry; 680 } 681 } else { 682 tmp = vma_prev(&vmi); 683 if (tmp && vm_end_gap(tmp) > gap) { 684 high_limit = tmp->vm_start; 685 vma_iter_reset(&vmi); 686 goto retry; 687 } 688 } 689 690 return gap; 691 } 692 693 /* 694 * Determine if the allocation needs to ensure that there is no 695 * existing mapping within it's guard gaps, for use as start_gap. 696 */ 697 static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) 698 { 699 if (vm_flags & VM_SHADOW_STACK) 700 return PAGE_SIZE; 701 702 return 0; 703 } 704 705 /* 706 * Search for an unmapped address range. 707 * 708 * We are looking for a range that: 709 * - does not intersect with any VMA; 710 * - is contained within the [low_limit, high_limit) interval; 711 * - is at least the desired size. 712 * - satisfies (begin_addr & align_mask) == (align_offset & align_mask) 713 */ 714 unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info) 715 { 716 unsigned long addr; 717 718 if (info->flags & VM_UNMAPPED_AREA_TOPDOWN) 719 addr = unmapped_area_topdown(info); 720 else 721 addr = unmapped_area(info); 722 723 trace_vm_unmapped_area(addr, info); 724 return addr; 725 } 726 727 /* Get an address range which is currently unmapped. 728 * For shmat() with addr=0. 729 * 730 * Ugly calling convention alert: 731 * Return value with the low bits set means error value, 732 * ie 733 * if (ret & ~PAGE_MASK) 734 * error = ret; 735 * 736 * This function "knows" that -ENOMEM has the bits set. 737 */ 738 unsigned long 739 generic_get_unmapped_area(struct file *filp, unsigned long addr, 740 unsigned long len, unsigned long pgoff, 741 unsigned long flags, vm_flags_t vm_flags) 742 { 743 struct mm_struct *mm = current->mm; 744 struct vm_area_struct *vma, *prev; 745 struct vm_unmapped_area_info info = {}; 746 const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags); 747 748 if (len > mmap_end - mmap_min_addr) 749 return -ENOMEM; 750 751 if (flags & MAP_FIXED) 752 return addr; 753 754 if (addr) { 755 addr = PAGE_ALIGN(addr); 756 vma = find_vma_prev(mm, addr, &prev); 757 if (mmap_end - len >= addr && addr >= mmap_min_addr && 758 (!vma || addr + len <= vm_start_gap(vma)) && 759 (!prev || addr >= vm_end_gap(prev))) 760 return addr; 761 } 762 763 info.length = len; 764 info.low_limit = mm->mmap_base; 765 info.high_limit = mmap_end; 766 info.start_gap = stack_guard_placement(vm_flags); 767 if (filp && is_file_hugepages(filp)) 768 info.align_mask = huge_page_mask_align(filp); 769 return vm_unmapped_area(&info); 770 } 771 772 #ifndef HAVE_ARCH_UNMAPPED_AREA 773 unsigned long 774 arch_get_unmapped_area(struct file *filp, unsigned long addr, 775 unsigned long len, unsigned long pgoff, 776 unsigned long flags, vm_flags_t vm_flags) 777 { 778 return generic_get_unmapped_area(filp, addr, len, pgoff, flags, 779 vm_flags); 780 } 781 #endif 782 783 /* 784 * This mmap-allocator allocates new areas top-down from below the 785 * stack's low limit (the base): 786 */ 787 unsigned long 788 generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr, 789 unsigned long len, unsigned long pgoff, 790 unsigned long flags, vm_flags_t vm_flags) 791 { 792 struct vm_area_struct *vma, *prev; 793 struct mm_struct *mm = current->mm; 794 struct vm_unmapped_area_info info = {}; 795 const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags); 796 797 /* requested length too big for entire address space */ 798 if (len > mmap_end - mmap_min_addr) 799 return -ENOMEM; 800 801 if (flags & MAP_FIXED) 802 return addr; 803 804 /* requesting a specific address */ 805 if (addr) { 806 addr = PAGE_ALIGN(addr); 807 vma = find_vma_prev(mm, addr, &prev); 808 if (mmap_end - len >= addr && addr >= mmap_min_addr && 809 (!vma || addr + len <= vm_start_gap(vma)) && 810 (!prev || addr >= vm_end_gap(prev))) 811 return addr; 812 } 813 814 info.flags = VM_UNMAPPED_AREA_TOPDOWN; 815 info.length = len; 816 info.low_limit = PAGE_SIZE; 817 info.high_limit = arch_get_mmap_base(addr, mm->mmap_base); 818 info.start_gap = stack_guard_placement(vm_flags); 819 if (filp && is_file_hugepages(filp)) 820 info.align_mask = huge_page_mask_align(filp); 821 addr = vm_unmapped_area(&info); 822 823 /* 824 * A failed mmap() very likely causes application failure, 825 * so fall back to the bottom-up function here. This scenario 826 * can happen with large stack limits and large mmap() 827 * allocations. 828 */ 829 if (offset_in_page(addr)) { 830 VM_BUG_ON(addr != -ENOMEM); 831 info.flags = 0; 832 info.low_limit = TASK_UNMAPPED_BASE; 833 info.high_limit = mmap_end; 834 addr = vm_unmapped_area(&info); 835 } 836 837 return addr; 838 } 839 840 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN 841 unsigned long 842 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, 843 unsigned long len, unsigned long pgoff, 844 unsigned long flags, vm_flags_t vm_flags) 845 { 846 return generic_get_unmapped_area_topdown(filp, addr, len, pgoff, flags, 847 vm_flags); 848 } 849 #endif 850 851 unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm, struct file *filp, 852 unsigned long addr, unsigned long len, 853 unsigned long pgoff, unsigned long flags, 854 vm_flags_t vm_flags) 855 { 856 if (test_bit(MMF_TOPDOWN, &mm->flags)) 857 return arch_get_unmapped_area_topdown(filp, addr, len, pgoff, 858 flags, vm_flags); 859 return arch_get_unmapped_area(filp, addr, len, pgoff, flags, vm_flags); 860 } 861 862 unsigned long 863 __get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, 864 unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags) 865 { 866 unsigned long (*get_area)(struct file *, unsigned long, 867 unsigned long, unsigned long, unsigned long) 868 = NULL; 869 870 unsigned long error = arch_mmap_check(addr, len, flags); 871 if (error) 872 return error; 873 874 /* Careful about overflows.. */ 875 if (len > TASK_SIZE) 876 return -ENOMEM; 877 878 if (file) { 879 if (file->f_op->get_unmapped_area) 880 get_area = file->f_op->get_unmapped_area; 881 } else if (flags & MAP_SHARED) { 882 /* 883 * mmap_region() will call shmem_zero_setup() to create a file, 884 * so use shmem's get_unmapped_area in case it can be huge. 885 */ 886 get_area = shmem_get_unmapped_area; 887 } 888 889 /* Always treat pgoff as zero for anonymous memory. */ 890 if (!file) 891 pgoff = 0; 892 893 if (get_area) { 894 addr = get_area(file, addr, len, pgoff, flags); 895 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && !file 896 && !addr /* no hint */ 897 && IS_ALIGNED(len, PMD_SIZE)) { 898 /* Ensures that larger anonymous mappings are THP aligned. */ 899 addr = thp_get_unmapped_area_vmflags(file, addr, len, 900 pgoff, flags, vm_flags); 901 } else { 902 addr = mm_get_unmapped_area_vmflags(current->mm, file, addr, len, 903 pgoff, flags, vm_flags); 904 } 905 if (IS_ERR_VALUE(addr)) 906 return addr; 907 908 if (addr > TASK_SIZE - len) 909 return -ENOMEM; 910 if (offset_in_page(addr)) 911 return -EINVAL; 912 913 error = security_mmap_addr(addr); 914 return error ? error : addr; 915 } 916 917 unsigned long 918 mm_get_unmapped_area(struct mm_struct *mm, struct file *file, 919 unsigned long addr, unsigned long len, 920 unsigned long pgoff, unsigned long flags) 921 { 922 if (test_bit(MMF_TOPDOWN, &mm->flags)) 923 return arch_get_unmapped_area_topdown(file, addr, len, pgoff, flags, 0); 924 return arch_get_unmapped_area(file, addr, len, pgoff, flags, 0); 925 } 926 EXPORT_SYMBOL(mm_get_unmapped_area); 927 928 /** 929 * find_vma_intersection() - Look up the first VMA which intersects the interval 930 * @mm: The process address space. 931 * @start_addr: The inclusive start user address. 932 * @end_addr: The exclusive end user address. 933 * 934 * Returns: The first VMA within the provided range, %NULL otherwise. Assumes 935 * start_addr < end_addr. 936 */ 937 struct vm_area_struct *find_vma_intersection(struct mm_struct *mm, 938 unsigned long start_addr, 939 unsigned long end_addr) 940 { 941 unsigned long index = start_addr; 942 943 mmap_assert_locked(mm); 944 return mt_find(&mm->mm_mt, &index, end_addr - 1); 945 } 946 EXPORT_SYMBOL(find_vma_intersection); 947 948 /** 949 * find_vma() - Find the VMA for a given address, or the next VMA. 950 * @mm: The mm_struct to check 951 * @addr: The address 952 * 953 * Returns: The VMA associated with addr, or the next VMA. 954 * May return %NULL in the case of no VMA at addr or above. 955 */ 956 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) 957 { 958 unsigned long index = addr; 959 960 mmap_assert_locked(mm); 961 return mt_find(&mm->mm_mt, &index, ULONG_MAX); 962 } 963 EXPORT_SYMBOL(find_vma); 964 965 /** 966 * find_vma_prev() - Find the VMA for a given address, or the next vma and 967 * set %pprev to the previous VMA, if any. 968 * @mm: The mm_struct to check 969 * @addr: The address 970 * @pprev: The pointer to set to the previous VMA 971 * 972 * Note that RCU lock is missing here since the external mmap_lock() is used 973 * instead. 974 * 975 * Returns: The VMA associated with @addr, or the next vma. 976 * May return %NULL in the case of no vma at addr or above. 977 */ 978 struct vm_area_struct * 979 find_vma_prev(struct mm_struct *mm, unsigned long addr, 980 struct vm_area_struct **pprev) 981 { 982 struct vm_area_struct *vma; 983 VMA_ITERATOR(vmi, mm, addr); 984 985 vma = vma_iter_load(&vmi); 986 *pprev = vma_prev(&vmi); 987 if (!vma) 988 vma = vma_next(&vmi); 989 return vma; 990 } 991 992 /* 993 * Verify that the stack growth is acceptable and 994 * update accounting. This is shared with both the 995 * grow-up and grow-down cases. 996 */ 997 static int acct_stack_growth(struct vm_area_struct *vma, 998 unsigned long size, unsigned long grow) 999 { 1000 struct mm_struct *mm = vma->vm_mm; 1001 unsigned long new_start; 1002 1003 /* address space limit tests */ 1004 if (!may_expand_vm(mm, vma->vm_flags, grow)) 1005 return -ENOMEM; 1006 1007 /* Stack limit test */ 1008 if (size > rlimit(RLIMIT_STACK)) 1009 return -ENOMEM; 1010 1011 /* mlock limit tests */ 1012 if (!mlock_future_ok(mm, vma->vm_flags, grow << PAGE_SHIFT)) 1013 return -ENOMEM; 1014 1015 /* Check to ensure the stack will not grow into a hugetlb-only region */ 1016 new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start : 1017 vma->vm_end - size; 1018 if (is_hugepage_only_range(vma->vm_mm, new_start, size)) 1019 return -EFAULT; 1020 1021 /* 1022 * Overcommit.. This must be the final test, as it will 1023 * update security statistics. 1024 */ 1025 if (security_vm_enough_memory_mm(mm, grow)) 1026 return -ENOMEM; 1027 1028 return 0; 1029 } 1030 1031 #if defined(CONFIG_STACK_GROWSUP) 1032 /* 1033 * PA-RISC uses this for its stack. 1034 * vma is the last one with address > vma->vm_end. Have to extend vma. 1035 */ 1036 static int expand_upwards(struct vm_area_struct *vma, unsigned long address) 1037 { 1038 struct mm_struct *mm = vma->vm_mm; 1039 struct vm_area_struct *next; 1040 unsigned long gap_addr; 1041 int error = 0; 1042 VMA_ITERATOR(vmi, mm, vma->vm_start); 1043 1044 if (!(vma->vm_flags & VM_GROWSUP)) 1045 return -EFAULT; 1046 1047 mmap_assert_write_locked(mm); 1048 1049 /* Guard against exceeding limits of the address space. */ 1050 address &= PAGE_MASK; 1051 if (address >= (TASK_SIZE & PAGE_MASK)) 1052 return -ENOMEM; 1053 address += PAGE_SIZE; 1054 1055 /* Enforce stack_guard_gap */ 1056 gap_addr = address + stack_guard_gap; 1057 1058 /* Guard against overflow */ 1059 if (gap_addr < address || gap_addr > TASK_SIZE) 1060 gap_addr = TASK_SIZE; 1061 1062 next = find_vma_intersection(mm, vma->vm_end, gap_addr); 1063 if (next && vma_is_accessible(next)) { 1064 if (!(next->vm_flags & VM_GROWSUP)) 1065 return -ENOMEM; 1066 /* Check that both stack segments have the same anon_vma? */ 1067 } 1068 1069 if (next) 1070 vma_iter_prev_range_limit(&vmi, address); 1071 1072 vma_iter_config(&vmi, vma->vm_start, address); 1073 if (vma_iter_prealloc(&vmi, vma)) 1074 return -ENOMEM; 1075 1076 /* We must make sure the anon_vma is allocated. */ 1077 if (unlikely(anon_vma_prepare(vma))) { 1078 vma_iter_free(&vmi); 1079 return -ENOMEM; 1080 } 1081 1082 /* Lock the VMA before expanding to prevent concurrent page faults */ 1083 vma_start_write(vma); 1084 /* We update the anon VMA tree. */ 1085 anon_vma_lock_write(vma->anon_vma); 1086 1087 /* Somebody else might have raced and expanded it already */ 1088 if (address > vma->vm_end) { 1089 unsigned long size, grow; 1090 1091 size = address - vma->vm_start; 1092 grow = (address - vma->vm_end) >> PAGE_SHIFT; 1093 1094 error = -ENOMEM; 1095 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) { 1096 error = acct_stack_growth(vma, size, grow); 1097 if (!error) { 1098 if (vma->vm_flags & VM_LOCKED) 1099 mm->locked_vm += grow; 1100 vm_stat_account(mm, vma->vm_flags, grow); 1101 anon_vma_interval_tree_pre_update_vma(vma); 1102 vma->vm_end = address; 1103 /* Overwrite old entry in mtree. */ 1104 vma_iter_store(&vmi, vma); 1105 anon_vma_interval_tree_post_update_vma(vma); 1106 1107 perf_event_mmap(vma); 1108 } 1109 } 1110 } 1111 anon_vma_unlock_write(vma->anon_vma); 1112 vma_iter_free(&vmi); 1113 validate_mm(mm); 1114 return error; 1115 } 1116 #endif /* CONFIG_STACK_GROWSUP */ 1117 1118 /* 1119 * vma is the first one with address < vma->vm_start. Have to extend vma. 1120 * mmap_lock held for writing. 1121 */ 1122 int expand_downwards(struct vm_area_struct *vma, unsigned long address) 1123 { 1124 struct mm_struct *mm = vma->vm_mm; 1125 struct vm_area_struct *prev; 1126 int error = 0; 1127 VMA_ITERATOR(vmi, mm, vma->vm_start); 1128 1129 if (!(vma->vm_flags & VM_GROWSDOWN)) 1130 return -EFAULT; 1131 1132 mmap_assert_write_locked(mm); 1133 1134 address &= PAGE_MASK; 1135 if (address < mmap_min_addr || address < FIRST_USER_ADDRESS) 1136 return -EPERM; 1137 1138 /* Enforce stack_guard_gap */ 1139 prev = vma_prev(&vmi); 1140 /* Check that both stack segments have the same anon_vma? */ 1141 if (prev) { 1142 if (!(prev->vm_flags & VM_GROWSDOWN) && 1143 vma_is_accessible(prev) && 1144 (address - prev->vm_end < stack_guard_gap)) 1145 return -ENOMEM; 1146 } 1147 1148 if (prev) 1149 vma_iter_next_range_limit(&vmi, vma->vm_start); 1150 1151 vma_iter_config(&vmi, address, vma->vm_end); 1152 if (vma_iter_prealloc(&vmi, vma)) 1153 return -ENOMEM; 1154 1155 /* We must make sure the anon_vma is allocated. */ 1156 if (unlikely(anon_vma_prepare(vma))) { 1157 vma_iter_free(&vmi); 1158 return -ENOMEM; 1159 } 1160 1161 /* Lock the VMA before expanding to prevent concurrent page faults */ 1162 vma_start_write(vma); 1163 /* We update the anon VMA tree. */ 1164 anon_vma_lock_write(vma->anon_vma); 1165 1166 /* Somebody else might have raced and expanded it already */ 1167 if (address < vma->vm_start) { 1168 unsigned long size, grow; 1169 1170 size = vma->vm_end - address; 1171 grow = (vma->vm_start - address) >> PAGE_SHIFT; 1172 1173 error = -ENOMEM; 1174 if (grow <= vma->vm_pgoff) { 1175 error = acct_stack_growth(vma, size, grow); 1176 if (!error) { 1177 if (vma->vm_flags & VM_LOCKED) 1178 mm->locked_vm += grow; 1179 vm_stat_account(mm, vma->vm_flags, grow); 1180 anon_vma_interval_tree_pre_update_vma(vma); 1181 vma->vm_start = address; 1182 vma->vm_pgoff -= grow; 1183 /* Overwrite old entry in mtree. */ 1184 vma_iter_store(&vmi, vma); 1185 anon_vma_interval_tree_post_update_vma(vma); 1186 1187 perf_event_mmap(vma); 1188 } 1189 } 1190 } 1191 anon_vma_unlock_write(vma->anon_vma); 1192 vma_iter_free(&vmi); 1193 validate_mm(mm); 1194 return error; 1195 } 1196 1197 /* enforced gap between the expanding stack and other mappings. */ 1198 unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT; 1199 1200 static int __init cmdline_parse_stack_guard_gap(char *p) 1201 { 1202 unsigned long val; 1203 char *endptr; 1204 1205 val = simple_strtoul(p, &endptr, 10); 1206 if (!*endptr) 1207 stack_guard_gap = val << PAGE_SHIFT; 1208 1209 return 1; 1210 } 1211 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap); 1212 1213 #ifdef CONFIG_STACK_GROWSUP 1214 int expand_stack_locked(struct vm_area_struct *vma, unsigned long address) 1215 { 1216 return expand_upwards(vma, address); 1217 } 1218 1219 struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr) 1220 { 1221 struct vm_area_struct *vma, *prev; 1222 1223 addr &= PAGE_MASK; 1224 vma = find_vma_prev(mm, addr, &prev); 1225 if (vma && (vma->vm_start <= addr)) 1226 return vma; 1227 if (!prev) 1228 return NULL; 1229 if (expand_stack_locked(prev, addr)) 1230 return NULL; 1231 if (prev->vm_flags & VM_LOCKED) 1232 populate_vma_page_range(prev, addr, prev->vm_end, NULL); 1233 return prev; 1234 } 1235 #else 1236 int expand_stack_locked(struct vm_area_struct *vma, unsigned long address) 1237 { 1238 return expand_downwards(vma, address); 1239 } 1240 1241 struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr) 1242 { 1243 struct vm_area_struct *vma; 1244 unsigned long start; 1245 1246 addr &= PAGE_MASK; 1247 vma = find_vma(mm, addr); 1248 if (!vma) 1249 return NULL; 1250 if (vma->vm_start <= addr) 1251 return vma; 1252 start = vma->vm_start; 1253 if (expand_stack_locked(vma, addr)) 1254 return NULL; 1255 if (vma->vm_flags & VM_LOCKED) 1256 populate_vma_page_range(vma, addr, start, NULL); 1257 return vma; 1258 } 1259 #endif 1260 1261 #if defined(CONFIG_STACK_GROWSUP) 1262 1263 #define vma_expand_up(vma,addr) expand_upwards(vma, addr) 1264 #define vma_expand_down(vma, addr) (-EFAULT) 1265 1266 #else 1267 1268 #define vma_expand_up(vma,addr) (-EFAULT) 1269 #define vma_expand_down(vma, addr) expand_downwards(vma, addr) 1270 1271 #endif 1272 1273 /* 1274 * expand_stack(): legacy interface for page faulting. Don't use unless 1275 * you have to. 1276 * 1277 * This is called with the mm locked for reading, drops the lock, takes 1278 * the lock for writing, tries to look up a vma again, expands it if 1279 * necessary, and downgrades the lock to reading again. 1280 * 1281 * If no vma is found or it can't be expanded, it returns NULL and has 1282 * dropped the lock. 1283 */ 1284 struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr) 1285 { 1286 struct vm_area_struct *vma, *prev; 1287 1288 mmap_read_unlock(mm); 1289 if (mmap_write_lock_killable(mm)) 1290 return NULL; 1291 1292 vma = find_vma_prev(mm, addr, &prev); 1293 if (vma && vma->vm_start <= addr) 1294 goto success; 1295 1296 if (prev && !vma_expand_up(prev, addr)) { 1297 vma = prev; 1298 goto success; 1299 } 1300 1301 if (vma && !vma_expand_down(vma, addr)) 1302 goto success; 1303 1304 mmap_write_unlock(mm); 1305 return NULL; 1306 1307 success: 1308 mmap_write_downgrade(mm); 1309 return vma; 1310 } 1311 1312 /* do_munmap() - Wrapper function for non-maple tree aware do_munmap() calls. 1313 * @mm: The mm_struct 1314 * @start: The start address to munmap 1315 * @len: The length to be munmapped. 1316 * @uf: The userfaultfd list_head 1317 * 1318 * Return: 0 on success, error otherwise. 1319 */ 1320 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, 1321 struct list_head *uf) 1322 { 1323 VMA_ITERATOR(vmi, mm, start); 1324 1325 return do_vmi_munmap(&vmi, mm, start, len, uf, false); 1326 } 1327 1328 unsigned long mmap_region(struct file *file, unsigned long addr, 1329 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff, 1330 struct list_head *uf) 1331 { 1332 unsigned long ret; 1333 bool writable_file_mapping = false; 1334 1335 /* Check to see if MDWE is applicable. */ 1336 if (map_deny_write_exec(vm_flags, vm_flags)) 1337 return -EACCES; 1338 1339 /* Allow architectures to sanity-check the vm_flags. */ 1340 if (!arch_validate_flags(vm_flags)) 1341 return -EINVAL; 1342 1343 /* Map writable and ensure this isn't a sealed memfd. */ 1344 if (file && is_shared_maywrite(vm_flags)) { 1345 int error = mapping_map_writable(file->f_mapping); 1346 1347 if (error) 1348 return error; 1349 writable_file_mapping = true; 1350 } 1351 1352 ret = __mmap_region(file, addr, len, vm_flags, pgoff, uf); 1353 1354 /* Clear our write mapping regardless of error. */ 1355 if (writable_file_mapping) 1356 mapping_unmap_writable(file->f_mapping); 1357 1358 validate_mm(current->mm); 1359 return ret; 1360 } 1361 1362 static int __vm_munmap(unsigned long start, size_t len, bool unlock) 1363 { 1364 int ret; 1365 struct mm_struct *mm = current->mm; 1366 LIST_HEAD(uf); 1367 VMA_ITERATOR(vmi, mm, start); 1368 1369 if (mmap_write_lock_killable(mm)) 1370 return -EINTR; 1371 1372 ret = do_vmi_munmap(&vmi, mm, start, len, &uf, unlock); 1373 if (ret || !unlock) 1374 mmap_write_unlock(mm); 1375 1376 userfaultfd_unmap_complete(mm, &uf); 1377 return ret; 1378 } 1379 1380 int vm_munmap(unsigned long start, size_t len) 1381 { 1382 return __vm_munmap(start, len, false); 1383 } 1384 EXPORT_SYMBOL(vm_munmap); 1385 1386 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) 1387 { 1388 addr = untagged_addr(addr); 1389 return __vm_munmap(addr, len, true); 1390 } 1391 1392 1393 /* 1394 * Emulation of deprecated remap_file_pages() syscall. 1395 */ 1396 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, 1397 unsigned long, prot, unsigned long, pgoff, unsigned long, flags) 1398 { 1399 1400 struct mm_struct *mm = current->mm; 1401 struct vm_area_struct *vma; 1402 unsigned long populate = 0; 1403 unsigned long ret = -EINVAL; 1404 struct file *file; 1405 vm_flags_t vm_flags; 1406 1407 pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/mm/remap_file_pages.rst.\n", 1408 current->comm, current->pid); 1409 1410 if (prot) 1411 return ret; 1412 start = start & PAGE_MASK; 1413 size = size & PAGE_MASK; 1414 1415 if (start + size <= start) 1416 return ret; 1417 1418 /* Does pgoff wrap? */ 1419 if (pgoff + (size >> PAGE_SHIFT) < pgoff) 1420 return ret; 1421 1422 if (mmap_read_lock_killable(mm)) 1423 return -EINTR; 1424 1425 /* 1426 * Look up VMA under read lock first so we can perform the security 1427 * without holding locks (which can be problematic). We reacquire a 1428 * write lock later and check nothing changed underneath us. 1429 */ 1430 vma = vma_lookup(mm, start); 1431 1432 if (!vma || !(vma->vm_flags & VM_SHARED)) { 1433 mmap_read_unlock(mm); 1434 return -EINVAL; 1435 } 1436 1437 prot |= vma->vm_flags & VM_READ ? PROT_READ : 0; 1438 prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0; 1439 prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0; 1440 1441 flags &= MAP_NONBLOCK; 1442 flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE; 1443 if (vma->vm_flags & VM_LOCKED) 1444 flags |= MAP_LOCKED; 1445 1446 /* Save vm_flags used to calculate prot and flags, and recheck later. */ 1447 vm_flags = vma->vm_flags; 1448 file = get_file(vma->vm_file); 1449 1450 mmap_read_unlock(mm); 1451 1452 /* Call outside mmap_lock to be consistent with other callers. */ 1453 ret = security_mmap_file(file, prot, flags); 1454 if (ret) { 1455 fput(file); 1456 return ret; 1457 } 1458 1459 ret = -EINVAL; 1460 1461 /* OK security check passed, take write lock + let it rip. */ 1462 if (mmap_write_lock_killable(mm)) { 1463 fput(file); 1464 return -EINTR; 1465 } 1466 1467 vma = vma_lookup(mm, start); 1468 1469 if (!vma) 1470 goto out; 1471 1472 /* Make sure things didn't change under us. */ 1473 if (vma->vm_flags != vm_flags) 1474 goto out; 1475 if (vma->vm_file != file) 1476 goto out; 1477 1478 if (start + size > vma->vm_end) { 1479 VMA_ITERATOR(vmi, mm, vma->vm_end); 1480 struct vm_area_struct *next, *prev = vma; 1481 1482 for_each_vma_range(vmi, next, start + size) { 1483 /* hole between vmas ? */ 1484 if (next->vm_start != prev->vm_end) 1485 goto out; 1486 1487 if (next->vm_file != vma->vm_file) 1488 goto out; 1489 1490 if (next->vm_flags != vma->vm_flags) 1491 goto out; 1492 1493 if (start + size <= next->vm_end) 1494 break; 1495 1496 prev = next; 1497 } 1498 1499 if (!next) 1500 goto out; 1501 } 1502 1503 ret = do_mmap(vma->vm_file, start, size, 1504 prot, flags, 0, pgoff, &populate, NULL); 1505 out: 1506 mmap_write_unlock(mm); 1507 fput(file); 1508 if (populate) 1509 mm_populate(ret, populate); 1510 if (!IS_ERR_VALUE(ret)) 1511 ret = 0; 1512 return ret; 1513 } 1514 1515 /* 1516 * do_brk_flags() - Increase the brk vma if the flags match. 1517 * @vmi: The vma iterator 1518 * @addr: The start address 1519 * @len: The length of the increase 1520 * @vma: The vma, 1521 * @flags: The VMA Flags 1522 * 1523 * Extend the brk VMA from addr to addr + len. If the VMA is NULL or the flags 1524 * do not match then create a new anonymous VMA. Eventually we may be able to 1525 * do some brk-specific accounting here. 1526 */ 1527 static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma, 1528 unsigned long addr, unsigned long len, unsigned long flags) 1529 { 1530 struct mm_struct *mm = current->mm; 1531 1532 /* 1533 * Check against address space limits by the changed size 1534 * Note: This happens *after* clearing old mappings in some code paths. 1535 */ 1536 flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags; 1537 if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT)) 1538 return -ENOMEM; 1539 1540 if (mm->map_count > sysctl_max_map_count) 1541 return -ENOMEM; 1542 1543 if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT)) 1544 return -ENOMEM; 1545 1546 /* 1547 * Expand the existing vma if possible; Note that singular lists do not 1548 * occur after forking, so the expand will only happen on new VMAs. 1549 */ 1550 if (vma && vma->vm_end == addr) { 1551 VMG_STATE(vmg, mm, vmi, addr, addr + len, flags, PHYS_PFN(addr)); 1552 1553 vmg.prev = vma; 1554 /* vmi is positioned at prev, which this mode expects. */ 1555 vmg.merge_flags = VMG_FLAG_JUST_EXPAND; 1556 1557 if (vma_merge_new_range(&vmg)) 1558 goto out; 1559 else if (vmg_nomem(&vmg)) 1560 goto unacct_fail; 1561 } 1562 1563 if (vma) 1564 vma_iter_next_range(vmi); 1565 /* create a vma struct for an anonymous mapping */ 1566 vma = vm_area_alloc(mm); 1567 if (!vma) 1568 goto unacct_fail; 1569 1570 vma_set_anonymous(vma); 1571 vma_set_range(vma, addr, addr + len, addr >> PAGE_SHIFT); 1572 vm_flags_init(vma, flags); 1573 vma->vm_page_prot = vm_get_page_prot(flags); 1574 vma_start_write(vma); 1575 if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL)) 1576 goto mas_store_fail; 1577 1578 mm->map_count++; 1579 validate_mm(mm); 1580 ksm_add_vma(vma); 1581 out: 1582 perf_event_mmap(vma); 1583 mm->total_vm += len >> PAGE_SHIFT; 1584 mm->data_vm += len >> PAGE_SHIFT; 1585 if (flags & VM_LOCKED) 1586 mm->locked_vm += (len >> PAGE_SHIFT); 1587 vm_flags_set(vma, VM_SOFTDIRTY); 1588 return 0; 1589 1590 mas_store_fail: 1591 vm_area_free(vma); 1592 unacct_fail: 1593 vm_unacct_memory(len >> PAGE_SHIFT); 1594 return -ENOMEM; 1595 } 1596 1597 int vm_brk_flags(unsigned long addr, unsigned long request, unsigned long flags) 1598 { 1599 struct mm_struct *mm = current->mm; 1600 struct vm_area_struct *vma = NULL; 1601 unsigned long len; 1602 int ret; 1603 bool populate; 1604 LIST_HEAD(uf); 1605 VMA_ITERATOR(vmi, mm, addr); 1606 1607 len = PAGE_ALIGN(request); 1608 if (len < request) 1609 return -ENOMEM; 1610 if (!len) 1611 return 0; 1612 1613 /* Until we need other flags, refuse anything except VM_EXEC. */ 1614 if ((flags & (~VM_EXEC)) != 0) 1615 return -EINVAL; 1616 1617 if (mmap_write_lock_killable(mm)) 1618 return -EINTR; 1619 1620 ret = check_brk_limits(addr, len); 1621 if (ret) 1622 goto limits_failed; 1623 1624 ret = do_vmi_munmap(&vmi, mm, addr, len, &uf, 0); 1625 if (ret) 1626 goto munmap_failed; 1627 1628 vma = vma_prev(&vmi); 1629 ret = do_brk_flags(&vmi, vma, addr, len, flags); 1630 populate = ((mm->def_flags & VM_LOCKED) != 0); 1631 mmap_write_unlock(mm); 1632 userfaultfd_unmap_complete(mm, &uf); 1633 if (populate && !ret) 1634 mm_populate(addr, len); 1635 return ret; 1636 1637 munmap_failed: 1638 limits_failed: 1639 mmap_write_unlock(mm); 1640 return ret; 1641 } 1642 EXPORT_SYMBOL(vm_brk_flags); 1643 1644 /* Release all mmaps. */ 1645 void exit_mmap(struct mm_struct *mm) 1646 { 1647 struct mmu_gather tlb; 1648 struct vm_area_struct *vma; 1649 unsigned long nr_accounted = 0; 1650 VMA_ITERATOR(vmi, mm, 0); 1651 int count = 0; 1652 1653 /* mm's last user has gone, and its about to be pulled down */ 1654 mmu_notifier_release(mm); 1655 1656 mmap_read_lock(mm); 1657 arch_exit_mmap(mm); 1658 1659 vma = vma_next(&vmi); 1660 if (!vma || unlikely(xa_is_zero(vma))) { 1661 /* Can happen if dup_mmap() received an OOM */ 1662 mmap_read_unlock(mm); 1663 mmap_write_lock(mm); 1664 goto destroy; 1665 } 1666 1667 lru_add_drain(); 1668 flush_cache_mm(mm); 1669 tlb_gather_mmu_fullmm(&tlb, mm); 1670 /* update_hiwater_rss(mm) here? but nobody should be looking */ 1671 /* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */ 1672 unmap_vmas(&tlb, &vmi.mas, vma, 0, ULONG_MAX, ULONG_MAX, false); 1673 mmap_read_unlock(mm); 1674 1675 /* 1676 * Set MMF_OOM_SKIP to hide this task from the oom killer/reaper 1677 * because the memory has been already freed. 1678 */ 1679 set_bit(MMF_OOM_SKIP, &mm->flags); 1680 mmap_write_lock(mm); 1681 mt_clear_in_rcu(&mm->mm_mt); 1682 vma_iter_set(&vmi, vma->vm_end); 1683 free_pgtables(&tlb, &vmi.mas, vma, FIRST_USER_ADDRESS, 1684 USER_PGTABLES_CEILING, true); 1685 tlb_finish_mmu(&tlb); 1686 1687 /* 1688 * Walk the list again, actually closing and freeing it, with preemption 1689 * enabled, without holding any MM locks besides the unreachable 1690 * mmap_write_lock. 1691 */ 1692 vma_iter_set(&vmi, vma->vm_end); 1693 do { 1694 if (vma->vm_flags & VM_ACCOUNT) 1695 nr_accounted += vma_pages(vma); 1696 remove_vma(vma, /* unreachable = */ true); 1697 count++; 1698 cond_resched(); 1699 vma = vma_next(&vmi); 1700 } while (vma && likely(!xa_is_zero(vma))); 1701 1702 BUG_ON(count != mm->map_count); 1703 1704 trace_exit_mmap(mm); 1705 destroy: 1706 __mt_destroy(&mm->mm_mt); 1707 mmap_write_unlock(mm); 1708 vm_unacct_memory(nr_accounted); 1709 } 1710 1711 /* Insert vm structure into process list sorted by address 1712 * and into the inode's i_mmap tree. If vm_file is non-NULL 1713 * then i_mmap_rwsem is taken here. 1714 */ 1715 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma) 1716 { 1717 unsigned long charged = vma_pages(vma); 1718 1719 1720 if (find_vma_intersection(mm, vma->vm_start, vma->vm_end)) 1721 return -ENOMEM; 1722 1723 if ((vma->vm_flags & VM_ACCOUNT) && 1724 security_vm_enough_memory_mm(mm, charged)) 1725 return -ENOMEM; 1726 1727 /* 1728 * The vm_pgoff of a purely anonymous vma should be irrelevant 1729 * until its first write fault, when page's anon_vma and index 1730 * are set. But now set the vm_pgoff it will almost certainly 1731 * end up with (unless mremap moves it elsewhere before that 1732 * first wfault), so /proc/pid/maps tells a consistent story. 1733 * 1734 * By setting it to reflect the virtual start address of the 1735 * vma, merges and splits can happen in a seamless way, just 1736 * using the existing file pgoff checks and manipulations. 1737 * Similarly in do_mmap and in do_brk_flags. 1738 */ 1739 if (vma_is_anonymous(vma)) { 1740 BUG_ON(vma->anon_vma); 1741 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT; 1742 } 1743 1744 if (vma_link(mm, vma)) { 1745 if (vma->vm_flags & VM_ACCOUNT) 1746 vm_unacct_memory(charged); 1747 return -ENOMEM; 1748 } 1749 1750 return 0; 1751 } 1752 1753 /* 1754 * Return true if the calling process may expand its vm space by the passed 1755 * number of pages 1756 */ 1757 bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages) 1758 { 1759 if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT) 1760 return false; 1761 1762 if (is_data_mapping(flags) && 1763 mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) { 1764 /* Workaround for Valgrind */ 1765 if (rlimit(RLIMIT_DATA) == 0 && 1766 mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT) 1767 return true; 1768 1769 pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n", 1770 current->comm, current->pid, 1771 (mm->data_vm + npages) << PAGE_SHIFT, 1772 rlimit(RLIMIT_DATA), 1773 ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data"); 1774 1775 if (!ignore_rlimit_data) 1776 return false; 1777 } 1778 1779 return true; 1780 } 1781 1782 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages) 1783 { 1784 WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm)+npages); 1785 1786 if (is_exec_mapping(flags)) 1787 mm->exec_vm += npages; 1788 else if (is_stack_mapping(flags)) 1789 mm->stack_vm += npages; 1790 else if (is_data_mapping(flags)) 1791 mm->data_vm += npages; 1792 } 1793 1794 static vm_fault_t special_mapping_fault(struct vm_fault *vmf); 1795 1796 /* 1797 * Close hook, called for unmap() and on the old vma for mremap(). 1798 * 1799 * Having a close hook prevents vma merging regardless of flags. 1800 */ 1801 static void special_mapping_close(struct vm_area_struct *vma) 1802 { 1803 const struct vm_special_mapping *sm = vma->vm_private_data; 1804 1805 if (sm->close) 1806 sm->close(sm, vma); 1807 } 1808 1809 static const char *special_mapping_name(struct vm_area_struct *vma) 1810 { 1811 return ((struct vm_special_mapping *)vma->vm_private_data)->name; 1812 } 1813 1814 static int special_mapping_mremap(struct vm_area_struct *new_vma) 1815 { 1816 struct vm_special_mapping *sm = new_vma->vm_private_data; 1817 1818 if (WARN_ON_ONCE(current->mm != new_vma->vm_mm)) 1819 return -EFAULT; 1820 1821 if (sm->mremap) 1822 return sm->mremap(sm, new_vma); 1823 1824 return 0; 1825 } 1826 1827 static int special_mapping_split(struct vm_area_struct *vma, unsigned long addr) 1828 { 1829 /* 1830 * Forbid splitting special mappings - kernel has expectations over 1831 * the number of pages in mapping. Together with VM_DONTEXPAND 1832 * the size of vma should stay the same over the special mapping's 1833 * lifetime. 1834 */ 1835 return -EINVAL; 1836 } 1837 1838 static const struct vm_operations_struct special_mapping_vmops = { 1839 .close = special_mapping_close, 1840 .fault = special_mapping_fault, 1841 .mremap = special_mapping_mremap, 1842 .name = special_mapping_name, 1843 /* vDSO code relies that VVAR can't be accessed remotely */ 1844 .access = NULL, 1845 .may_split = special_mapping_split, 1846 }; 1847 1848 static vm_fault_t special_mapping_fault(struct vm_fault *vmf) 1849 { 1850 struct vm_area_struct *vma = vmf->vma; 1851 pgoff_t pgoff; 1852 struct page **pages; 1853 struct vm_special_mapping *sm = vma->vm_private_data; 1854 1855 if (sm->fault) 1856 return sm->fault(sm, vmf->vma, vmf); 1857 1858 pages = sm->pages; 1859 1860 for (pgoff = vmf->pgoff; pgoff && *pages; ++pages) 1861 pgoff--; 1862 1863 if (*pages) { 1864 struct page *page = *pages; 1865 get_page(page); 1866 vmf->page = page; 1867 return 0; 1868 } 1869 1870 return VM_FAULT_SIGBUS; 1871 } 1872 1873 static struct vm_area_struct *__install_special_mapping( 1874 struct mm_struct *mm, 1875 unsigned long addr, unsigned long len, 1876 unsigned long vm_flags, void *priv, 1877 const struct vm_operations_struct *ops) 1878 { 1879 int ret; 1880 struct vm_area_struct *vma; 1881 1882 vma = vm_area_alloc(mm); 1883 if (unlikely(vma == NULL)) 1884 return ERR_PTR(-ENOMEM); 1885 1886 vma_set_range(vma, addr, addr + len, 0); 1887 vm_flags_init(vma, (vm_flags | mm->def_flags | 1888 VM_DONTEXPAND | VM_SOFTDIRTY) & ~VM_LOCKED_MASK); 1889 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 1890 1891 vma->vm_ops = ops; 1892 vma->vm_private_data = priv; 1893 1894 ret = insert_vm_struct(mm, vma); 1895 if (ret) 1896 goto out; 1897 1898 vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT); 1899 1900 perf_event_mmap(vma); 1901 1902 return vma; 1903 1904 out: 1905 vm_area_free(vma); 1906 return ERR_PTR(ret); 1907 } 1908 1909 bool vma_is_special_mapping(const struct vm_area_struct *vma, 1910 const struct vm_special_mapping *sm) 1911 { 1912 return vma->vm_private_data == sm && 1913 vma->vm_ops == &special_mapping_vmops; 1914 } 1915 1916 /* 1917 * Called with mm->mmap_lock held for writing. 1918 * Insert a new vma covering the given region, with the given flags. 1919 * Its pages are supplied by the given array of struct page *. 1920 * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated. 1921 * The region past the last page supplied will always produce SIGBUS. 1922 * The array pointer and the pages it points to are assumed to stay alive 1923 * for as long as this mapping might exist. 1924 */ 1925 struct vm_area_struct *_install_special_mapping( 1926 struct mm_struct *mm, 1927 unsigned long addr, unsigned long len, 1928 unsigned long vm_flags, const struct vm_special_mapping *spec) 1929 { 1930 return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec, 1931 &special_mapping_vmops); 1932 } 1933 1934 /* 1935 * initialise the percpu counter for VM 1936 */ 1937 void __init mmap_init(void) 1938 { 1939 int ret; 1940 1941 ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL); 1942 VM_BUG_ON(ret); 1943 } 1944 1945 /* 1946 * Initialise sysctl_user_reserve_kbytes. 1947 * 1948 * This is intended to prevent a user from starting a single memory hogging 1949 * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER 1950 * mode. 1951 * 1952 * The default value is min(3% of free memory, 128MB) 1953 * 128MB is enough to recover with sshd/login, bash, and top/kill. 1954 */ 1955 static int init_user_reserve(void) 1956 { 1957 unsigned long free_kbytes; 1958 1959 free_kbytes = K(global_zone_page_state(NR_FREE_PAGES)); 1960 1961 sysctl_user_reserve_kbytes = min(free_kbytes / 32, SZ_128K); 1962 return 0; 1963 } 1964 subsys_initcall(init_user_reserve); 1965 1966 /* 1967 * Initialise sysctl_admin_reserve_kbytes. 1968 * 1969 * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin 1970 * to log in and kill a memory hogging process. 1971 * 1972 * Systems with more than 256MB will reserve 8MB, enough to recover 1973 * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will 1974 * only reserve 3% of free pages by default. 1975 */ 1976 static int init_admin_reserve(void) 1977 { 1978 unsigned long free_kbytes; 1979 1980 free_kbytes = K(global_zone_page_state(NR_FREE_PAGES)); 1981 1982 sysctl_admin_reserve_kbytes = min(free_kbytes / 32, SZ_8K); 1983 return 0; 1984 } 1985 subsys_initcall(init_admin_reserve); 1986 1987 /* 1988 * Reinititalise user and admin reserves if memory is added or removed. 1989 * 1990 * The default user reserve max is 128MB, and the default max for the 1991 * admin reserve is 8MB. These are usually, but not always, enough to 1992 * enable recovery from a memory hogging process using login/sshd, a shell, 1993 * and tools like top. It may make sense to increase or even disable the 1994 * reserve depending on the existence of swap or variations in the recovery 1995 * tools. So, the admin may have changed them. 1996 * 1997 * If memory is added and the reserves have been eliminated or increased above 1998 * the default max, then we'll trust the admin. 1999 * 2000 * If memory is removed and there isn't enough free memory, then we 2001 * need to reset the reserves. 2002 * 2003 * Otherwise keep the reserve set by the admin. 2004 */ 2005 static int reserve_mem_notifier(struct notifier_block *nb, 2006 unsigned long action, void *data) 2007 { 2008 unsigned long tmp, free_kbytes; 2009 2010 switch (action) { 2011 case MEM_ONLINE: 2012 /* Default max is 128MB. Leave alone if modified by operator. */ 2013 tmp = sysctl_user_reserve_kbytes; 2014 if (tmp > 0 && tmp < SZ_128K) 2015 init_user_reserve(); 2016 2017 /* Default max is 8MB. Leave alone if modified by operator. */ 2018 tmp = sysctl_admin_reserve_kbytes; 2019 if (tmp > 0 && tmp < SZ_8K) 2020 init_admin_reserve(); 2021 2022 break; 2023 case MEM_OFFLINE: 2024 free_kbytes = K(global_zone_page_state(NR_FREE_PAGES)); 2025 2026 if (sysctl_user_reserve_kbytes > free_kbytes) { 2027 init_user_reserve(); 2028 pr_info("vm.user_reserve_kbytes reset to %lu\n", 2029 sysctl_user_reserve_kbytes); 2030 } 2031 2032 if (sysctl_admin_reserve_kbytes > free_kbytes) { 2033 init_admin_reserve(); 2034 pr_info("vm.admin_reserve_kbytes reset to %lu\n", 2035 sysctl_admin_reserve_kbytes); 2036 } 2037 break; 2038 default: 2039 break; 2040 } 2041 return NOTIFY_OK; 2042 } 2043 2044 static int __meminit init_reserve_notifier(void) 2045 { 2046 if (hotplug_memory_notifier(reserve_mem_notifier, DEFAULT_CALLBACK_PRI)) 2047 pr_err("Failed registering memory add/remove notifier for admin reserve\n"); 2048 2049 return 0; 2050 } 2051 subsys_initcall(init_reserve_notifier); 2052 2053 /* 2054 * Relocate a VMA downwards by shift bytes. There cannot be any VMAs between 2055 * this VMA and its relocated range, which will now reside at [vma->vm_start - 2056 * shift, vma->vm_end - shift). 2057 * 2058 * This function is almost certainly NOT what you want for anything other than 2059 * early executable temporary stack relocation. 2060 */ 2061 int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift) 2062 { 2063 /* 2064 * The process proceeds as follows: 2065 * 2066 * 1) Use shift to calculate the new vma endpoints. 2067 * 2) Extend vma to cover both the old and new ranges. This ensures the 2068 * arguments passed to subsequent functions are consistent. 2069 * 3) Move vma's page tables to the new range. 2070 * 4) Free up any cleared pgd range. 2071 * 5) Shrink the vma to cover only the new range. 2072 */ 2073 2074 struct mm_struct *mm = vma->vm_mm; 2075 unsigned long old_start = vma->vm_start; 2076 unsigned long old_end = vma->vm_end; 2077 unsigned long length = old_end - old_start; 2078 unsigned long new_start = old_start - shift; 2079 unsigned long new_end = old_end - shift; 2080 VMA_ITERATOR(vmi, mm, new_start); 2081 VMG_STATE(vmg, mm, &vmi, new_start, old_end, 0, vma->vm_pgoff); 2082 struct vm_area_struct *next; 2083 struct mmu_gather tlb; 2084 2085 BUG_ON(new_start > new_end); 2086 2087 /* 2088 * ensure there are no vmas between where we want to go 2089 * and where we are 2090 */ 2091 if (vma != vma_next(&vmi)) 2092 return -EFAULT; 2093 2094 vma_iter_prev_range(&vmi); 2095 /* 2096 * cover the whole range: [new_start, old_end) 2097 */ 2098 vmg.vma = vma; 2099 if (vma_expand(&vmg)) 2100 return -ENOMEM; 2101 2102 /* 2103 * move the page tables downwards, on failure we rely on 2104 * process cleanup to remove whatever mess we made. 2105 */ 2106 if (length != move_page_tables(vma, old_start, 2107 vma, new_start, length, false, true)) 2108 return -ENOMEM; 2109 2110 lru_add_drain(); 2111 tlb_gather_mmu(&tlb, mm); 2112 next = vma_next(&vmi); 2113 if (new_end > old_start) { 2114 /* 2115 * when the old and new regions overlap clear from new_end. 2116 */ 2117 free_pgd_range(&tlb, new_end, old_end, new_end, 2118 next ? next->vm_start : USER_PGTABLES_CEILING); 2119 } else { 2120 /* 2121 * otherwise, clean from old_start; this is done to not touch 2122 * the address space in [new_end, old_start) some architectures 2123 * have constraints on va-space that make this illegal (IA64) - 2124 * for the others its just a little faster. 2125 */ 2126 free_pgd_range(&tlb, old_start, old_end, new_end, 2127 next ? next->vm_start : USER_PGTABLES_CEILING); 2128 } 2129 tlb_finish_mmu(&tlb); 2130 2131 vma_prev(&vmi); 2132 /* Shrink the vma to just the new range */ 2133 return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff); 2134 } 2135