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 vma_flags_t vma_flags = vma->flags; 84 pgprot_t vm_page_prot; 85 86 vm_page_prot = vma_pgprot_modify(vma->vm_page_prot, vma_flags); 87 if (vma_wants_writenotify(vma, vm_page_prot)) { 88 vma_flags_clear(&vma_flags, VMA_SHARED_BIT); 89 vm_page_prot = vma_pgprot_modify(vm_page_prot, vma_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 const struct mm_struct *mm = current->mm; 106 const bool is_def_locked = 107 vma_flags_test(&mm->def_vma_flags, VMA_LOCKED_BIT); 108 unsigned long mapped_addr; 109 110 mapped_addr = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); 111 if (IS_ERR_VALUE(mapped_addr)) 112 return mapped_addr; 113 114 return mlock_future_ok(mm, is_def_locked, len) ? 0 : -EAGAIN; 115 } 116 117 SYSCALL_DEFINE1(brk, unsigned long, brk) 118 { 119 unsigned long newbrk, oldbrk, origbrk; 120 struct mm_struct *mm = current->mm; 121 struct vm_area_struct *brkvma, *next = NULL; 122 unsigned long min_brk; 123 bool populate = false; 124 LIST_HEAD(uf); 125 struct vma_iterator vmi; 126 127 if (mmap_write_lock_killable(mm)) 128 return -EINTR; 129 130 origbrk = mm->brk; 131 132 min_brk = mm->start_brk; 133 #ifdef CONFIG_COMPAT_BRK 134 /* 135 * CONFIG_COMPAT_BRK can still be overridden by setting 136 * randomize_va_space to 2, which will still cause mm->start_brk 137 * to be arbitrarily shifted 138 */ 139 if (!current->brk_randomized) 140 min_brk = mm->end_data; 141 #endif 142 if (brk < min_brk) 143 goto out; 144 145 /* 146 * Check against rlimit here. If this check is done later after the test 147 * of oldbrk with newbrk then it can escape the test and let the data 148 * segment grow beyond its set limit the in case where the limit is 149 * not page aligned -Ram Gupta 150 */ 151 if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk, 152 mm->end_data, mm->start_data)) 153 goto out; 154 155 newbrk = PAGE_ALIGN(brk); 156 oldbrk = PAGE_ALIGN(mm->brk); 157 if (oldbrk == newbrk) { 158 mm->brk = brk; 159 goto success; 160 } 161 162 /* Always allow shrinking brk. */ 163 if (brk <= mm->brk) { 164 /* Search one past newbrk */ 165 vma_iter_init(&vmi, mm, newbrk); 166 brkvma = vma_find(&vmi, oldbrk); 167 if (!brkvma || brkvma->vm_start >= oldbrk) 168 goto out; /* mapping intersects with an existing non-brk vma. */ 169 /* 170 * mm->brk must be protected by write mmap_lock. 171 * do_vmi_align_munmap() will drop the lock on success, so 172 * update it before calling do_vma_munmap(). 173 */ 174 mm->brk = brk; 175 if (do_vmi_align_munmap(&vmi, brkvma, mm, newbrk, oldbrk, &uf, 176 /* unlock = */ true)) 177 goto out; 178 179 goto success_unlocked; 180 } 181 182 if (check_brk_limits(oldbrk, newbrk - oldbrk)) 183 goto out; 184 185 /* 186 * Only check if the next VMA is within the stack_guard_gap of the 187 * expansion area 188 */ 189 vma_iter_init(&vmi, mm, oldbrk); 190 next = vma_find(&vmi, newbrk + PAGE_SIZE + stack_guard_gap); 191 if (next && newbrk + PAGE_SIZE > vm_start_gap(next)) 192 goto out; 193 194 brkvma = vma_prev_limit(&vmi, mm->start_brk); 195 /* Ok, looks good - let it rip. */ 196 if (do_brk_flags(&vmi, brkvma, oldbrk, newbrk - oldbrk, 197 EMPTY_VMA_FLAGS) < 0) 198 goto out; 199 200 mm->brk = brk; 201 if (vma_flags_test(&mm->def_vma_flags, VMA_LOCKED_BIT)) 202 populate = true; 203 204 success: 205 mmap_write_unlock(mm); 206 success_unlocked: 207 userfaultfd_unmap_complete(mm, &uf); 208 if (populate) 209 mm_populate(oldbrk, newbrk - oldbrk); 210 return brk; 211 212 out: 213 mm->brk = origbrk; 214 mmap_write_unlock(mm); 215 return origbrk; 216 } 217 218 /* 219 * If a hint addr is less than mmap_min_addr change hint to be as 220 * low as possible but still greater than mmap_min_addr 221 */ 222 static inline unsigned long round_hint_to_min(unsigned long hint) 223 { 224 hint &= PAGE_MASK; 225 if (((void *)hint != NULL) && 226 (hint < mmap_min_addr)) 227 return PAGE_ALIGN(mmap_min_addr); 228 return hint; 229 } 230 231 bool mlock_future_ok(const struct mm_struct *mm, bool is_vma_locked, 232 unsigned long bytes) 233 { 234 unsigned long locked_pages, limit_pages; 235 236 if (!is_vma_locked || capable(CAP_IPC_LOCK)) 237 return true; 238 239 locked_pages = bytes >> PAGE_SHIFT; 240 locked_pages += mm->locked_vm; 241 242 limit_pages = rlimit(RLIMIT_MEMLOCK); 243 limit_pages >>= PAGE_SHIFT; 244 245 return locked_pages <= limit_pages; 246 } 247 248 static inline u64 file_mmap_size_max(struct file *file, struct inode *inode) 249 { 250 if (S_ISREG(inode->i_mode)) 251 return MAX_LFS_FILESIZE; 252 253 if (S_ISBLK(inode->i_mode)) 254 return MAX_LFS_FILESIZE; 255 256 if (S_ISSOCK(inode->i_mode)) 257 return MAX_LFS_FILESIZE; 258 259 /* Special "we do even unsigned file positions" case */ 260 if (file->f_op->fop_flags & FOP_UNSIGNED_OFFSET) 261 return 0; 262 263 /* Yes, random drivers might want more. But I'm tired of buggy drivers */ 264 return ULONG_MAX; 265 } 266 267 static inline bool file_mmap_ok(struct file *file, struct inode *inode, 268 unsigned long pgoff, unsigned long len) 269 { 270 u64 maxsize = file_mmap_size_max(file, inode); 271 272 if (maxsize && len > maxsize) 273 return false; 274 maxsize -= len; 275 if (pgoff > maxsize >> PAGE_SHIFT) 276 return false; 277 return true; 278 } 279 280 /** 281 * do_mmap() - Perform a userland memory mapping into the current process 282 * address space of length @len with protection bits @prot, mmap flags @flags 283 * (from which VMA flags will be inferred), and any additional VMA flags to 284 * apply @vma_flags. If this is a file-backed mapping then the file is specified 285 * in @file and page offset into the file via @pgoff. 286 * 287 * This function does not perform security checks on the file and assumes, if 288 * @uf is non-NULL, the caller has provided a list head to track unmap events 289 * for userfaultfd @uf. 290 * 291 * It also simply indicates whether memory population is required by setting 292 * @populate, which must be non-NULL, expecting the caller to actually perform 293 * this task itself if appropriate. 294 * 295 * This function will invoke architecture-specific (and if provided and 296 * relevant, file system-specific) logic to determine the most appropriate 297 * unmapped area in which to place the mapping if not MAP_FIXED. 298 * 299 * Callers which require userland mmap() behaviour should invoke vm_mmap(), 300 * which is also exported for module use. 301 * 302 * Those which require this behaviour less security checks, userfaultfd and 303 * populate behaviour, and who handle the mmap write lock themselves, should 304 * call this function. 305 * 306 * Note that the returned address may reside within a merged VMA if an 307 * appropriate merge were to take place, so it doesn't necessarily specify the 308 * start of a VMA, rather only the start of a valid mapped range of length 309 * @len bytes, rounded down to the nearest page size. 310 * 311 * The caller must write-lock current->mm->mmap_lock. 312 * 313 * @file: An optional struct file pointer describing the file which is to be 314 * mapped, if a file-backed mapping. 315 * @addr: If non-zero, hints at (or if @flags has MAP_FIXED set, specifies) the 316 * address at which to perform this mapping. See mmap (2) for details. Must be 317 * page-aligned. 318 * @len: The length of the mapping. Will be page-aligned and must be at least 1 319 * page in size. 320 * @prot: Protection bits describing access required to the mapping. See mmap 321 * (2) for details. 322 * @flags: Flags specifying how the mapping should be performed, see mmap (2) 323 * for details. 324 * @vma_flags: VMA flags which should be set by default, or EMPTY_VMA_FLAGS 325 * otherwise. 326 * @pgoff: Page offset into the @file if file-backed, should be 0 otherwise. 327 * @populate: A pointer to a value which will be set to 0 if no population of 328 * the range is required, or the number of bytes to populate if it is. Must be 329 * non-NULL. See mmap (2) for details as to under what circumstances population 330 * of the range occurs. 331 * @uf: An optional pointer to a list head to track userfaultfd unmap events 332 * should unmapping events arise. If provided, it is up to the caller to manage 333 * this. 334 * 335 * Returns: Either an error, or the address at which the requested mapping has 336 * been performed. 337 */ 338 unsigned long do_mmap(struct file *file, unsigned long addr, 339 unsigned long len, unsigned long prot, 340 unsigned long flags, vma_flags_t vma_flags, 341 unsigned long pgoff, unsigned long *populate, 342 struct list_head *uf) 343 { 344 struct mm_struct *mm = current->mm; 345 int pkey = 0; 346 347 *populate = 0; 348 349 mmap_assert_write_locked(mm); 350 351 if (!len) 352 return -EINVAL; 353 354 /* 355 * Does the application expect PROT_READ to imply PROT_EXEC? 356 * 357 * (the exception is when the underlying filesystem is noexec 358 * mounted, in which case we don't add PROT_EXEC.) 359 */ 360 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 361 if (!(file && path_noexec(&file->f_path))) 362 prot |= PROT_EXEC; 363 364 /* force arch specific MAP_FIXED handling in get_unmapped_area */ 365 if (flags & MAP_FIXED_NOREPLACE) 366 flags |= MAP_FIXED; 367 368 if (!(flags & MAP_FIXED)) 369 addr = round_hint_to_min(addr); 370 371 /* Careful about overflows.. */ 372 len = PAGE_ALIGN(len); 373 if (!len) 374 return -ENOMEM; 375 376 /* offset overflow? */ 377 if ((pgoff + (len >> PAGE_SHIFT)) < pgoff) 378 return -EOVERFLOW; 379 380 /* Too many mappings? */ 381 if (mm->map_count > get_sysctl_max_map_count()) 382 return -ENOMEM; 383 384 /* 385 * addr is returned from get_unmapped_area, 386 * There are two cases: 387 * 1> MAP_FIXED == false 388 * unallocated memory, no need to check sealing. 389 * 1> MAP_FIXED == true 390 * sealing is checked inside mmap_region when 391 * do_vmi_munmap is called. 392 */ 393 394 if (prot == PROT_EXEC) { 395 pkey = execute_only_pkey(mm); 396 if (pkey < 0) 397 pkey = 0; 398 } 399 400 /* Do simple checking here so the lower-level routines won't have 401 * to. we assume access permissions have been handled by the open 402 * of the memory object, so we don't do any here. 403 */ 404 vma_flags_set_mask(&vma_flags, 405 legacy_to_vma_flags(calc_vm_prot_bits(prot, pkey))); 406 vma_flags_set_mask(&vma_flags, 407 legacy_to_vma_flags(calc_vm_flag_bits(file, flags))); 408 vma_flags_set_mask(&vma_flags, mm->def_vma_flags); 409 vma_flags_set(&vma_flags, VMA_MAYREAD_BIT, VMA_MAYWRITE_BIT, 410 VMA_MAYEXEC_BIT); 411 412 /* Obtain the address to map to. we verify (or select) it and ensure 413 * that it represents a valid section of the address space. 414 */ 415 addr = __get_unmapped_area(file, addr, len, pgoff, flags, vma_flags); 416 if (IS_ERR_VALUE(addr)) 417 return addr; 418 419 if (flags & MAP_FIXED_NOREPLACE) { 420 if (find_vma_intersection(mm, addr, addr + len)) 421 return -EEXIST; 422 } 423 424 if (flags & MAP_LOCKED) 425 if (!can_do_mlock()) 426 return -EPERM; 427 428 if (!mlock_future_ok(mm, vma_flags_test(&vma_flags, VMA_LOCKED_BIT), len)) 429 return -EAGAIN; 430 431 if (file) { 432 struct inode *inode = file_inode(file); 433 unsigned long flags_mask; 434 int err; 435 436 if (!file_mmap_ok(file, inode, pgoff, len)) 437 return -EOVERFLOW; 438 439 flags_mask = LEGACY_MAP_MASK; 440 if (file->f_op->fop_flags & FOP_MMAP_SYNC) 441 flags_mask |= MAP_SYNC; 442 443 switch (flags & MAP_TYPE) { 444 case MAP_SHARED: 445 /* 446 * Force use of MAP_SHARED_VALIDATE with non-legacy 447 * flags. E.g. MAP_SYNC is dangerous to use with 448 * MAP_SHARED as you don't know which consistency model 449 * you will get. We silently ignore unsupported flags 450 * with MAP_SHARED to preserve backward compatibility. 451 */ 452 flags &= LEGACY_MAP_MASK; 453 fallthrough; 454 case MAP_SHARED_VALIDATE: 455 if (flags & ~flags_mask) 456 return -EOPNOTSUPP; 457 if (prot & PROT_WRITE) { 458 if (!(file->f_mode & FMODE_WRITE)) 459 return -EACCES; 460 if (IS_SWAPFILE(file->f_mapping->host)) 461 return -ETXTBSY; 462 } 463 464 /* 465 * Make sure we don't allow writing to an append-only 466 * file.. 467 */ 468 if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE)) 469 return -EACCES; 470 471 vma_flags_set(&vma_flags, VMA_SHARED_BIT, VMA_MAYSHARE_BIT); 472 if (!(file->f_mode & FMODE_WRITE)) 473 vma_flags_clear(&vma_flags, VMA_MAYWRITE_BIT, 474 VMA_SHARED_BIT); 475 fallthrough; 476 case MAP_PRIVATE: 477 if (!(file->f_mode & FMODE_READ)) 478 return -EACCES; 479 if (path_noexec(&file->f_path)) { 480 if (vma_flags_test(&vma_flags, VMA_EXEC_BIT)) 481 return -EPERM; 482 vma_flags_clear(&vma_flags, VMA_MAYEXEC_BIT); 483 } 484 485 if (!can_mmap_file(file)) 486 return -ENODEV; 487 if (vma_flags_can_grow(&vma_flags)) 488 return -EINVAL; 489 break; 490 491 default: 492 return -EINVAL; 493 } 494 495 /* 496 * Check to see if we are violating any seals and update VMA 497 * flags if necessary to avoid future seal violations. 498 */ 499 err = memfd_check_seals_mmap(file, &vma_flags); 500 if (err) 501 return (unsigned long)err; 502 } else { 503 switch (flags & MAP_TYPE) { 504 case MAP_SHARED: 505 if (vma_flags_can_grow(&vma_flags)) 506 return -EINVAL; 507 /* 508 * Ignore pgoff. 509 */ 510 pgoff = 0; 511 vma_flags_set(&vma_flags, VMA_SHARED_BIT, VMA_MAYSHARE_BIT); 512 break; 513 case MAP_DROPPABLE: { 514 vma_flags_t droppable = VMA_DROPPABLE; 515 516 if (vma_flags_empty(&droppable)) 517 return -EOPNOTSUPP; 518 vma_flags_set_mask(&vma_flags, droppable); 519 520 /* 521 * A locked or stack area makes no sense to be droppable. 522 * 523 * Also, since droppable pages can just go away at any time 524 * it makes no sense to copy them on fork or dump them. 525 * 526 * And don't attempt to combine with hugetlb for now. 527 */ 528 if (flags & (MAP_LOCKED | MAP_HUGETLB)) 529 return -EINVAL; 530 if (vma_flags_can_grow(&vma_flags)) 531 return -EINVAL; 532 533 /* 534 * If the pages can be dropped, then it doesn't make 535 * sense to reserve them. 536 */ 537 vma_flags_set(&vma_flags, VMA_NORESERVE_BIT); 538 539 /* 540 * Likewise, they're volatile enough that they 541 * shouldn't survive forks or coredumps. 542 */ 543 vma_flags_set(&vma_flags, VMA_WIPEONFORK_BIT, 544 VMA_DONTDUMP_BIT); 545 546 fallthrough; 547 } 548 case MAP_PRIVATE: 549 /* 550 * Set pgoff according to addr for anon_vma. 551 */ 552 pgoff = addr >> PAGE_SHIFT; 553 break; 554 default: 555 return -EINVAL; 556 } 557 } 558 559 /* 560 * Set VMA_NORESERVE_BIT if we should not account for the memory use 561 * of this mapping. 562 */ 563 if (flags & MAP_NORESERVE) { 564 /* We honor MAP_NORESERVE if allowed to overcommit */ 565 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER) 566 vma_flags_set(&vma_flags, VMA_NORESERVE_BIT); 567 568 /* hugetlb applies strict overcommit unless MAP_NORESERVE */ 569 if (file && is_file_hugepages(file)) 570 vma_flags_set(&vma_flags, VMA_NORESERVE_BIT); 571 } 572 573 addr = mmap_region(file, addr, len, vma_flags, pgoff, uf); 574 if (!IS_ERR_VALUE(addr) && 575 (vma_flags_test(&vma_flags, VMA_LOCKED_BIT) || 576 (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE)) 577 *populate = len; 578 return addr; 579 } 580 581 unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len, 582 unsigned long prot, unsigned long flags, 583 unsigned long fd, unsigned long pgoff) 584 { 585 struct file *file = NULL; 586 unsigned long retval; 587 588 if (!(flags & MAP_ANONYMOUS)) { 589 audit_mmap_fd(fd, flags); 590 file = fget(fd); 591 if (!file) 592 return -EBADF; 593 if (is_file_hugepages(file)) { 594 len = ALIGN(len, huge_page_size(hstate_file(file))); 595 } else if (unlikely(flags & MAP_HUGETLB)) { 596 retval = -EINVAL; 597 goto out_fput; 598 } 599 } else if (flags & MAP_HUGETLB) { 600 struct hstate *hs; 601 602 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK); 603 if (!hs) 604 return -EINVAL; 605 606 len = ALIGN(len, huge_page_size(hs)); 607 /* 608 * VM_NORESERVE is used because the reservations will be 609 * taken when vm_ops->mmap() is called 610 */ 611 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, 612 mk_vma_flags(VMA_NORESERVE_BIT), 613 HUGETLB_ANONHUGE_INODE, 614 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK); 615 if (IS_ERR(file)) 616 return PTR_ERR(file); 617 } 618 619 retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff); 620 out_fput: 621 if (file) 622 fput(file); 623 return retval; 624 } 625 626 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len, 627 unsigned long, prot, unsigned long, flags, 628 unsigned long, fd, unsigned long, pgoff) 629 { 630 return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff); 631 } 632 633 #ifdef __ARCH_WANT_SYS_OLD_MMAP 634 struct mmap_arg_struct { 635 unsigned long addr; 636 unsigned long len; 637 unsigned long prot; 638 unsigned long flags; 639 unsigned long fd; 640 unsigned long offset; 641 }; 642 643 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) 644 { 645 struct mmap_arg_struct a; 646 647 if (copy_from_user(&a, arg, sizeof(a))) 648 return -EFAULT; 649 if (offset_in_page(a.offset)) 650 return -EINVAL; 651 652 return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, 653 a.offset >> PAGE_SHIFT); 654 } 655 #endif /* __ARCH_WANT_SYS_OLD_MMAP */ 656 657 /* 658 * Determine if the allocation needs to ensure that there is no 659 * existing mapping within it's guard gaps, for use as start_gap. 660 */ 661 static inline unsigned long stack_guard_placement(vma_flags_t vma_flags) 662 { 663 if (vma_flags_test_single_mask(&vma_flags, VMA_SHADOW_STACK)) 664 return PAGE_SIZE; 665 666 return 0; 667 } 668 669 /* 670 * Search for an unmapped address range. 671 * 672 * We are looking for a range that: 673 * - does not intersect with any VMA; 674 * - is contained within the [low_limit, high_limit) interval; 675 * - is at least the desired size. 676 * - satisfies (begin_addr & align_mask) == (align_offset & align_mask) 677 */ 678 unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info) 679 { 680 unsigned long addr; 681 682 if (info->flags & VM_UNMAPPED_AREA_TOPDOWN) 683 addr = unmapped_area_topdown(info); 684 else 685 addr = unmapped_area(info); 686 687 trace_vm_unmapped_area(addr, info); 688 return addr; 689 } 690 691 /* Get an address range which is currently unmapped. 692 * For shmat() with addr=0. 693 * 694 * Ugly calling convention alert: 695 * Return value with the low bits set means error value, 696 * ie 697 * if (ret & ~PAGE_MASK) 698 * error = ret; 699 * 700 * This function "knows" that -ENOMEM has the bits set. 701 */ 702 unsigned long 703 generic_get_unmapped_area(struct file *filp, unsigned long addr, 704 unsigned long len, unsigned long pgoff, 705 unsigned long flags, vma_flags_t vma_flags) 706 { 707 struct mm_struct *mm = current->mm; 708 struct vm_area_struct *vma, *prev; 709 struct vm_unmapped_area_info info = {}; 710 const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags); 711 712 if (len > mmap_end - mmap_min_addr) 713 return -ENOMEM; 714 715 if (flags & MAP_FIXED) 716 return addr; 717 718 if (addr) { 719 addr = PAGE_ALIGN(addr); 720 vma = find_vma_prev(mm, addr, &prev); 721 if (mmap_end - len >= addr && addr >= mmap_min_addr && 722 (!vma || addr + len <= vm_start_gap(vma)) && 723 (!prev || addr >= vm_end_gap(prev))) 724 return addr; 725 } 726 727 info.length = len; 728 info.low_limit = mm->mmap_base; 729 info.high_limit = mmap_end; 730 info.start_gap = stack_guard_placement(vma_flags); 731 if (filp && is_file_hugepages(filp)) 732 info.align_mask = huge_page_mask_align(filp); 733 return vm_unmapped_area(&info); 734 } 735 736 #ifndef HAVE_ARCH_UNMAPPED_AREA 737 unsigned long 738 arch_get_unmapped_area(struct file *filp, unsigned long addr, 739 unsigned long len, unsigned long pgoff, 740 unsigned long flags, vm_flags_t vm_flags) 741 { 742 return generic_get_unmapped_area(filp, addr, len, pgoff, flags, 743 legacy_to_vma_flags(vm_flags)); 744 } 745 #endif 746 747 /* 748 * This mmap-allocator allocates new areas top-down from below the 749 * stack's low limit (the base): 750 */ 751 unsigned long 752 generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr, 753 unsigned long len, unsigned long pgoff, 754 unsigned long flags, vma_flags_t vma_flags) 755 { 756 struct vm_area_struct *vma, *prev; 757 struct mm_struct *mm = current->mm; 758 struct vm_unmapped_area_info info = {}; 759 const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags); 760 761 /* requested length too big for entire address space */ 762 if (len > mmap_end - mmap_min_addr) 763 return -ENOMEM; 764 765 if (flags & MAP_FIXED) 766 return addr; 767 768 /* requesting a specific address */ 769 if (addr) { 770 addr = PAGE_ALIGN(addr); 771 vma = find_vma_prev(mm, addr, &prev); 772 if (mmap_end - len >= addr && addr >= mmap_min_addr && 773 (!vma || addr + len <= vm_start_gap(vma)) && 774 (!prev || addr >= vm_end_gap(prev))) 775 return addr; 776 } 777 778 info.flags = VM_UNMAPPED_AREA_TOPDOWN; 779 info.length = len; 780 info.low_limit = PAGE_SIZE; 781 info.high_limit = arch_get_mmap_base(addr, mm->mmap_base); 782 info.start_gap = stack_guard_placement(vma_flags); 783 if (filp && is_file_hugepages(filp)) 784 info.align_mask = huge_page_mask_align(filp); 785 addr = vm_unmapped_area(&info); 786 787 /* 788 * A failed mmap() very likely causes application failure, 789 * so fall back to the bottom-up function here. This scenario 790 * can happen with large stack limits and large mmap() 791 * allocations. 792 */ 793 if (offset_in_page(addr)) { 794 VM_BUG_ON(addr != -ENOMEM); 795 info.flags = 0; 796 info.low_limit = TASK_UNMAPPED_BASE; 797 info.high_limit = mmap_end; 798 addr = vm_unmapped_area(&info); 799 } 800 801 return addr; 802 } 803 804 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN 805 unsigned long 806 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, 807 unsigned long len, unsigned long pgoff, 808 unsigned long flags, vm_flags_t vm_flags) 809 { 810 return generic_get_unmapped_area_topdown(filp, addr, len, pgoff, flags, 811 legacy_to_vma_flags(vm_flags)); 812 } 813 #endif 814 815 unsigned long mm_get_unmapped_area_vmaflags(struct file *filp, unsigned long addr, 816 unsigned long len, unsigned long pgoff, unsigned long flags, 817 vma_flags_t vma_flags) 818 { 819 if (mm_flags_test(MMF_TOPDOWN, current->mm)) 820 return arch_get_unmapped_area_topdown(filp, addr, len, pgoff, 821 flags, vma_flags_to_legacy(vma_flags)); 822 return arch_get_unmapped_area(filp, addr, len, pgoff, flags, 823 vma_flags_to_legacy(vma_flags)); 824 } 825 826 unsigned long 827 __get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, 828 unsigned long pgoff, unsigned long flags, vma_flags_t vma_flags) 829 { 830 unsigned long (*get_area)(struct file *, unsigned long, 831 unsigned long, unsigned long, unsigned long) 832 = NULL; 833 834 unsigned long error = arch_mmap_check(addr, len, flags); 835 if (error) 836 return error; 837 838 /* Careful about overflows.. */ 839 if (len > TASK_SIZE) 840 return -ENOMEM; 841 842 if (file) { 843 if (file->f_op->get_unmapped_area) 844 get_area = file->f_op->get_unmapped_area; 845 } else if (flags & MAP_SHARED) { 846 /* 847 * mmap_region() will call shmem_zero_setup() to create a file, 848 * so use shmem's get_unmapped_area in case it can be huge. 849 */ 850 get_area = shmem_get_unmapped_area; 851 } 852 853 /* Always treat pgoff as zero for anonymous memory. */ 854 if (!file) 855 pgoff = 0; 856 857 if (get_area) { 858 addr = get_area(file, addr, len, pgoff, flags); 859 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && !file 860 && !addr /* no hint */ 861 && IS_ALIGNED(len, PMD_SIZE)) { 862 /* Ensures that larger anonymous mappings are THP aligned. */ 863 addr = thp_get_unmapped_area_vmaflags(file, addr, len, 864 pgoff, flags, vma_flags); 865 } else { 866 addr = mm_get_unmapped_area_vmaflags(file, addr, len, 867 pgoff, flags, vma_flags); 868 } 869 if (IS_ERR_VALUE(addr)) 870 return addr; 871 872 if (addr > TASK_SIZE - len) 873 return -ENOMEM; 874 if (offset_in_page(addr)) 875 return -EINVAL; 876 877 error = security_mmap_addr(addr); 878 return error ? error : addr; 879 } 880 881 unsigned long 882 mm_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, 883 unsigned long pgoff, unsigned long flags) 884 { 885 return mm_get_unmapped_area_vmaflags(file, addr, len, pgoff, flags, 886 EMPTY_VMA_FLAGS); 887 } 888 EXPORT_SYMBOL(mm_get_unmapped_area); 889 890 /** 891 * find_vma_intersection() - Look up the first VMA which intersects the interval 892 * @mm: The process address space. 893 * @start_addr: The inclusive start user address. 894 * @end_addr: The exclusive end user address. 895 * 896 * Returns: The first VMA within the provided range, %NULL otherwise. Assumes 897 * start_addr < end_addr. 898 */ 899 struct vm_area_struct *find_vma_intersection(struct mm_struct *mm, 900 unsigned long start_addr, 901 unsigned long end_addr) 902 { 903 unsigned long index = start_addr; 904 905 mmap_assert_locked(mm); 906 return mt_find(&mm->mm_mt, &index, end_addr - 1); 907 } 908 EXPORT_SYMBOL(find_vma_intersection); 909 910 /** 911 * find_vma() - Find the VMA for a given address, or the next VMA. 912 * @mm: The mm_struct to check 913 * @addr: The address 914 * 915 * Returns: The VMA associated with addr, or the next VMA. 916 * May return %NULL in the case of no VMA at addr or above. 917 */ 918 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) 919 { 920 unsigned long index = addr; 921 922 mmap_assert_locked(mm); 923 return mt_find(&mm->mm_mt, &index, ULONG_MAX); 924 } 925 EXPORT_SYMBOL(find_vma); 926 927 /** 928 * find_vma_prev() - Find the VMA for a given address, or the next vma and 929 * set %pprev to the previous VMA, if any. 930 * @mm: The mm_struct to check 931 * @addr: The address 932 * @pprev: The pointer to set to the previous VMA 933 * 934 * Note that RCU lock is missing here since the external mmap_lock() is used 935 * instead. 936 * 937 * Returns: The VMA associated with @addr, or the next vma. 938 * May return %NULL in the case of no vma at addr or above. 939 */ 940 struct vm_area_struct * 941 find_vma_prev(struct mm_struct *mm, unsigned long addr, 942 struct vm_area_struct **pprev) 943 { 944 struct vm_area_struct *vma; 945 VMA_ITERATOR(vmi, mm, addr); 946 947 vma = vma_iter_load(&vmi); 948 *pprev = vma_prev(&vmi); 949 if (!vma) 950 vma = vma_next(&vmi); 951 return vma; 952 } 953 954 /* enforced gap between the expanding stack and other mappings. */ 955 unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT; 956 957 static int __init cmdline_parse_stack_guard_gap(char *p) 958 { 959 unsigned long val; 960 char *endptr; 961 962 val = simple_strtoul(p, &endptr, 10); 963 if (!*endptr) 964 stack_guard_gap = val << PAGE_SHIFT; 965 966 return 1; 967 } 968 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap); 969 970 #ifdef CONFIG_STACK_GROWSUP 971 int expand_stack_locked(struct vm_area_struct *vma, unsigned long address) 972 { 973 return expand_upwards(vma, address); 974 } 975 976 struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr) 977 { 978 struct vm_area_struct *vma, *prev; 979 980 addr &= PAGE_MASK; 981 vma = find_vma_prev(mm, addr, &prev); 982 if (vma && (vma->vm_start <= addr)) 983 return vma; 984 if (!prev) 985 return NULL; 986 if (expand_stack_locked(prev, addr)) 987 return NULL; 988 if (vma_test(prev, VMA_LOCKED_BIT)) 989 populate_vma_page_range(prev, addr, prev->vm_end, NULL); 990 return prev; 991 } 992 #else 993 int expand_stack_locked(struct vm_area_struct *vma, unsigned long address) 994 { 995 return expand_downwards(vma, address); 996 } 997 998 struct vm_area_struct *find_extend_vma_locked(struct mm_struct *mm, unsigned long addr) 999 { 1000 struct vm_area_struct *vma; 1001 unsigned long start; 1002 1003 addr &= PAGE_MASK; 1004 vma = find_vma(mm, addr); 1005 if (!vma) 1006 return NULL; 1007 if (vma->vm_start <= addr) 1008 return vma; 1009 start = vma->vm_start; 1010 if (expand_stack_locked(vma, addr)) 1011 return NULL; 1012 if (vma_test(vma, VMA_LOCKED_BIT)) 1013 populate_vma_page_range(vma, addr, start, NULL); 1014 return vma; 1015 } 1016 #endif 1017 1018 #if defined(CONFIG_STACK_GROWSUP) 1019 1020 #define vma_expand_up(vma,addr) expand_upwards(vma, addr) 1021 #define vma_expand_down(vma, addr) (-EFAULT) 1022 1023 #else 1024 1025 #define vma_expand_up(vma,addr) (-EFAULT) 1026 #define vma_expand_down(vma, addr) expand_downwards(vma, addr) 1027 1028 #endif 1029 1030 /* 1031 * expand_stack(): legacy interface for page faulting. Don't use unless 1032 * you have to. 1033 * 1034 * This is called with the mm locked for reading, drops the lock, takes 1035 * the lock for writing, tries to look up a vma again, expands it if 1036 * necessary, and downgrades the lock to reading again. 1037 * 1038 * If no vma is found or it can't be expanded, it returns NULL and has 1039 * dropped the lock. 1040 */ 1041 struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr) 1042 { 1043 struct vm_area_struct *vma, *prev; 1044 1045 mmap_read_unlock(mm); 1046 if (mmap_write_lock_killable(mm)) 1047 return NULL; 1048 1049 vma = find_vma_prev(mm, addr, &prev); 1050 if (vma && vma->vm_start <= addr) 1051 goto success; 1052 1053 if (prev && !vma_expand_up(prev, addr)) { 1054 vma = prev; 1055 goto success; 1056 } 1057 1058 if (vma && !vma_expand_down(vma, addr)) 1059 goto success; 1060 1061 mmap_write_unlock(mm); 1062 return NULL; 1063 1064 success: 1065 mmap_write_downgrade(mm); 1066 return vma; 1067 } 1068 1069 /* do_munmap() - Wrapper function for non-maple tree aware do_munmap() calls. 1070 * @mm: The mm_struct 1071 * @start: The start address to munmap 1072 * @len: The length to be munmapped. 1073 * @uf: The userfaultfd list_head 1074 * 1075 * Return: 0 on success, error otherwise. 1076 */ 1077 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, 1078 struct list_head *uf) 1079 { 1080 VMA_ITERATOR(vmi, mm, start); 1081 1082 return do_vmi_munmap(&vmi, mm, start, len, uf, false); 1083 } 1084 1085 int vm_munmap(unsigned long start, size_t len) 1086 { 1087 return __vm_munmap(start, len, false); 1088 } 1089 EXPORT_SYMBOL(vm_munmap); 1090 1091 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) 1092 { 1093 addr = untagged_addr(addr); 1094 return __vm_munmap(addr, len, true); 1095 } 1096 1097 1098 /* 1099 * Emulation of deprecated remap_file_pages() syscall. 1100 */ 1101 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, 1102 unsigned long, prot, unsigned long, pgoff, unsigned long, flags) 1103 { 1104 1105 struct mm_struct *mm = current->mm; 1106 struct vm_area_struct *vma; 1107 unsigned long populate = 0; 1108 unsigned long ret = -EINVAL; 1109 struct file *file; 1110 vm_flags_t vm_flags; 1111 1112 pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/mm/remap_file_pages.rst.\n", 1113 current->comm, current->pid); 1114 1115 if (prot) 1116 return ret; 1117 start = start & PAGE_MASK; 1118 size = size & PAGE_MASK; 1119 1120 if (start + size <= start) 1121 return ret; 1122 1123 /* Does pgoff wrap? */ 1124 if (pgoff + (size >> PAGE_SHIFT) < pgoff) 1125 return ret; 1126 1127 if (mmap_read_lock_killable(mm)) 1128 return -EINTR; 1129 1130 /* 1131 * Look up VMA under read lock first so we can perform the security 1132 * without holding locks (which can be problematic). We reacquire a 1133 * write lock later and check nothing changed underneath us. 1134 */ 1135 vma = vma_lookup(mm, start); 1136 1137 if (!vma || !vma_test(vma, VMA_SHARED_BIT)) { 1138 mmap_read_unlock(mm); 1139 return -EINVAL; 1140 } 1141 1142 prot |= vma_test(vma, VMA_READ_BIT) ? PROT_READ : 0; 1143 prot |= vma_test(vma, VMA_WRITE_BIT) ? PROT_WRITE : 0; 1144 prot |= vma_test(vma, VMA_EXEC_BIT) ? PROT_EXEC : 0; 1145 1146 flags &= MAP_NONBLOCK; 1147 flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE; 1148 if (vma_test(vma, VMA_LOCKED_BIT)) 1149 flags |= MAP_LOCKED; 1150 1151 /* Save vm_flags used to calculate prot and flags, and recheck later. */ 1152 vm_flags = vma->vm_flags; 1153 file = get_file(vma->vm_file); 1154 1155 mmap_read_unlock(mm); 1156 1157 /* Call outside mmap_lock to be consistent with other callers. */ 1158 ret = security_mmap_file(file, prot, flags); 1159 if (ret) { 1160 fput(file); 1161 return ret; 1162 } 1163 1164 ret = -EINVAL; 1165 1166 /* OK security check passed, take write lock + let it rip. */ 1167 if (mmap_write_lock_killable(mm)) { 1168 fput(file); 1169 return -EINTR; 1170 } 1171 1172 vma = vma_lookup(mm, start); 1173 1174 if (!vma) 1175 goto out; 1176 1177 /* Make sure things didn't change under us. */ 1178 if (vma->vm_flags != vm_flags) 1179 goto out; 1180 if (vma->vm_file != file) 1181 goto out; 1182 1183 if (start + size > vma->vm_end) { 1184 VMA_ITERATOR(vmi, mm, vma->vm_end); 1185 struct vm_area_struct *next, *prev = vma; 1186 1187 for_each_vma_range(vmi, next, start + size) { 1188 /* hole between vmas ? */ 1189 if (next->vm_start != prev->vm_end) 1190 goto out; 1191 1192 if (next->vm_file != vma->vm_file) 1193 goto out; 1194 1195 if (next->vm_flags != vma->vm_flags) 1196 goto out; 1197 1198 if (start + size <= next->vm_end) 1199 break; 1200 1201 prev = next; 1202 } 1203 1204 if (!next) 1205 goto out; 1206 } 1207 1208 ret = do_mmap(vma->vm_file, start, size, 1209 prot, flags, EMPTY_VMA_FLAGS, pgoff, &populate, NULL); 1210 out: 1211 mmap_write_unlock(mm); 1212 fput(file); 1213 if (populate) 1214 mm_populate(ret, populate); 1215 if (!IS_ERR_VALUE(ret)) 1216 ret = 0; 1217 return ret; 1218 } 1219 1220 int vm_brk_flags(unsigned long addr, unsigned long request, bool is_exec) 1221 { 1222 const vma_flags_t vma_flags = is_exec ? 1223 mk_vma_flags(VMA_EXEC_BIT) : EMPTY_VMA_FLAGS; 1224 struct mm_struct *mm = current->mm; 1225 struct vm_area_struct *vma = NULL; 1226 unsigned long len; 1227 int ret; 1228 bool populate; 1229 LIST_HEAD(uf); 1230 VMA_ITERATOR(vmi, mm, addr); 1231 1232 len = PAGE_ALIGN(request); 1233 if (len < request) 1234 return -ENOMEM; 1235 if (!len) 1236 return 0; 1237 1238 if (mmap_write_lock_killable(mm)) 1239 return -EINTR; 1240 1241 ret = check_brk_limits(addr, len); 1242 if (ret) 1243 goto limits_failed; 1244 1245 ret = do_vmi_munmap(&vmi, mm, addr, len, &uf, 0); 1246 if (ret) 1247 goto munmap_failed; 1248 1249 vma = vma_prev(&vmi); 1250 ret = do_brk_flags(&vmi, vma, addr, len, vma_flags); 1251 populate = vma_flags_test(&mm->def_vma_flags, VMA_LOCKED_BIT); 1252 mmap_write_unlock(mm); 1253 userfaultfd_unmap_complete(mm, &uf); 1254 if (populate && !ret) 1255 mm_populate(addr, len); 1256 return ret; 1257 1258 munmap_failed: 1259 limits_failed: 1260 mmap_write_unlock(mm); 1261 return ret; 1262 } 1263 1264 static 1265 unsigned long tear_down_vmas(struct mm_struct *mm, struct vma_iterator *vmi, 1266 struct vm_area_struct *vma, unsigned long end) 1267 { 1268 unsigned long nr_accounted = 0; 1269 int count = 0; 1270 1271 mmap_assert_write_locked(mm); 1272 vma_iter_set(vmi, vma->vm_end); 1273 do { 1274 if (vma_test(vma, VMA_ACCOUNT_BIT)) 1275 nr_accounted += vma_pages(vma); 1276 vma_mark_detached(vma); 1277 remove_vma(vma); 1278 count++; 1279 cond_resched(); 1280 vma = vma_next(vmi); 1281 } while (vma && vma->vm_end <= end); 1282 1283 VM_WARN_ON_ONCE(count != mm->map_count); 1284 return nr_accounted; 1285 } 1286 1287 /* Release all mmaps. */ 1288 void exit_mmap(struct mm_struct *mm) 1289 { 1290 struct mmu_gather tlb; 1291 struct vm_area_struct *vma; 1292 unsigned long nr_accounted = 0; 1293 VMA_ITERATOR(vmi, mm, 0); 1294 struct unmap_desc unmap; 1295 1296 /* mm's last user has gone, and its about to be pulled down */ 1297 mmu_notifier_release(mm); 1298 1299 mmap_read_lock(mm); 1300 arch_exit_mmap(mm); 1301 1302 vma = vma_next(&vmi); 1303 if (!vma) { 1304 /* Can happen if dup_mmap() received an OOM */ 1305 mmap_read_unlock(mm); 1306 mmap_write_lock(mm); 1307 goto destroy; 1308 } 1309 1310 unmap_all_init(&unmap, &vmi, vma); 1311 flush_cache_mm(mm); 1312 tlb_gather_mmu_fullmm(&tlb, mm); 1313 /* update_hiwater_rss(mm) here? but nobody should be looking */ 1314 /* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */ 1315 unmap_vmas(&tlb, &unmap); 1316 mmap_read_unlock(mm); 1317 1318 /* 1319 * Set MMF_OOM_SKIP to hide this task from the oom killer/reaper 1320 * because the memory has been already freed. 1321 */ 1322 mm_flags_set(MMF_OOM_SKIP, mm); 1323 mmap_write_lock(mm); 1324 unmap.mm_wr_locked = true; 1325 mt_clear_in_rcu(&mm->mm_mt); 1326 unmap_pgtable_init(&unmap, &vmi); 1327 free_pgtables(&tlb, &unmap); 1328 tlb_finish_mmu(&tlb); 1329 1330 /* 1331 * Walk the list again, actually closing and freeing it, with preemption 1332 * enabled, without holding any MM locks besides the unreachable 1333 * mmap_write_lock. 1334 */ 1335 nr_accounted = tear_down_vmas(mm, &vmi, vma, ULONG_MAX); 1336 1337 destroy: 1338 __mt_destroy(&mm->mm_mt); 1339 trace_exit_mmap(mm); 1340 mmap_write_unlock(mm); 1341 vm_unacct_memory(nr_accounted); 1342 } 1343 1344 /* 1345 * Return true if the calling process may expand its vm space by the passed 1346 * number of pages 1347 */ 1348 bool may_expand_vm(struct mm_struct *mm, const vma_flags_t *vma_flags, 1349 unsigned long npages) 1350 { 1351 if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT) 1352 return false; 1353 1354 if (is_data_mapping_vma_flags(vma_flags) && 1355 mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) { 1356 /* Workaround for Valgrind */ 1357 if (rlimit(RLIMIT_DATA) == 0 && 1358 mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT) 1359 return true; 1360 1361 pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits%s.\n", 1362 current->comm, current->pid, 1363 (mm->data_vm + npages) << PAGE_SHIFT, 1364 rlimit(RLIMIT_DATA), 1365 ignore_rlimit_data ? "" : " or use boot option ignore_rlimit_data"); 1366 1367 if (!ignore_rlimit_data) 1368 return false; 1369 } 1370 1371 return true; 1372 } 1373 1374 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages) 1375 { 1376 WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm)+npages); 1377 1378 if (is_exec_mapping(flags)) 1379 mm->exec_vm += npages; 1380 else if (is_stack_mapping(flags)) 1381 mm->stack_vm += npages; 1382 else if (is_data_mapping(flags)) 1383 mm->data_vm += npages; 1384 } 1385 1386 static vm_fault_t special_mapping_fault(struct vm_fault *vmf); 1387 1388 /* 1389 * Close hook, called for unmap() and on the old vma for mremap(). 1390 * 1391 * Having a close hook prevents vma merging regardless of flags. 1392 */ 1393 static void special_mapping_close(struct vm_area_struct *vma) 1394 { 1395 const struct vm_special_mapping *sm = vma->vm_private_data; 1396 1397 if (sm->close) 1398 sm->close(sm, vma); 1399 } 1400 1401 static const char *special_mapping_name(struct vm_area_struct *vma) 1402 { 1403 return ((struct vm_special_mapping *)vma->vm_private_data)->name; 1404 } 1405 1406 static int special_mapping_mremap(struct vm_area_struct *new_vma) 1407 { 1408 struct vm_special_mapping *sm = new_vma->vm_private_data; 1409 1410 if (WARN_ON_ONCE(current->mm != new_vma->vm_mm)) 1411 return -EFAULT; 1412 1413 if (sm->mremap) 1414 return sm->mremap(sm, new_vma); 1415 1416 return 0; 1417 } 1418 1419 static int special_mapping_split(struct vm_area_struct *vma, unsigned long addr) 1420 { 1421 /* 1422 * Forbid splitting special mappings - kernel has expectations over 1423 * the number of pages in mapping. Together with VMA_DONTEXPAND_BIT 1424 * the size of vma should stay the same over the special mapping's 1425 * lifetime. 1426 */ 1427 return -EINVAL; 1428 } 1429 1430 static const struct vm_operations_struct special_mapping_vmops = { 1431 .close = special_mapping_close, 1432 .fault = special_mapping_fault, 1433 .mremap = special_mapping_mremap, 1434 .name = special_mapping_name, 1435 /* vDSO code relies that VVAR can't be accessed remotely */ 1436 .access = NULL, 1437 .may_split = special_mapping_split, 1438 }; 1439 1440 static vm_fault_t special_mapping_fault(struct vm_fault *vmf) 1441 { 1442 struct vm_area_struct *vma = vmf->vma; 1443 pgoff_t pgoff; 1444 struct page **pages; 1445 struct vm_special_mapping *sm = vma->vm_private_data; 1446 1447 if (sm->fault) 1448 return sm->fault(sm, vmf->vma, vmf); 1449 1450 pages = sm->pages; 1451 1452 for (pgoff = vmf->pgoff; pgoff && *pages; ++pages) 1453 pgoff--; 1454 1455 if (*pages) { 1456 struct page *page = *pages; 1457 get_page(page); 1458 vmf->page = page; 1459 return 0; 1460 } 1461 1462 return VM_FAULT_SIGBUS; 1463 } 1464 1465 bool vma_is_special_mapping(const struct vm_area_struct *vma, 1466 const struct vm_special_mapping *sm) 1467 { 1468 return vma->vm_private_data == sm && 1469 vma->vm_ops == &special_mapping_vmops; 1470 } 1471 1472 /* 1473 * Called with mm->mmap_lock held for writing. 1474 * Insert a new vma covering the given region, with the given flags. 1475 * Its pages are supplied by the given array of struct page *. 1476 * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated. 1477 * The region past the last page supplied will always produce SIGBUS. 1478 * The array pointer and the pages it points to are assumed to stay alive 1479 * for as long as this mapping might exist. 1480 */ 1481 struct vm_area_struct *_install_special_mapping( 1482 struct mm_struct *mm, 1483 unsigned long addr, unsigned long len, 1484 vm_flags_t vm_flags, const struct vm_special_mapping *spec) 1485 { 1486 return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec, 1487 &special_mapping_vmops); 1488 } 1489 1490 #ifdef CONFIG_SYSCTL 1491 #if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \ 1492 defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) 1493 int sysctl_legacy_va_layout; 1494 #endif 1495 1496 static const struct ctl_table mmap_table[] = { 1497 { 1498 .procname = "max_map_count", 1499 .data = &sysctl_max_map_count, 1500 .maxlen = sizeof(sysctl_max_map_count), 1501 .mode = 0644, 1502 .proc_handler = proc_dointvec_minmax, 1503 .extra1 = SYSCTL_ZERO, 1504 }, 1505 #if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \ 1506 defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) 1507 { 1508 .procname = "legacy_va_layout", 1509 .data = &sysctl_legacy_va_layout, 1510 .maxlen = sizeof(sysctl_legacy_va_layout), 1511 .mode = 0644, 1512 .proc_handler = proc_dointvec_minmax, 1513 .extra1 = SYSCTL_ZERO, 1514 }, 1515 #endif 1516 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS 1517 { 1518 .procname = "mmap_rnd_bits", 1519 .data = &mmap_rnd_bits, 1520 .maxlen = sizeof(mmap_rnd_bits), 1521 .mode = 0600, 1522 .proc_handler = proc_dointvec_minmax, 1523 .extra1 = (void *)&mmap_rnd_bits_min, 1524 .extra2 = (void *)&mmap_rnd_bits_max, 1525 }, 1526 #endif 1527 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS 1528 { 1529 .procname = "mmap_rnd_compat_bits", 1530 .data = &mmap_rnd_compat_bits, 1531 .maxlen = sizeof(mmap_rnd_compat_bits), 1532 .mode = 0600, 1533 .proc_handler = proc_dointvec_minmax, 1534 .extra1 = (void *)&mmap_rnd_compat_bits_min, 1535 .extra2 = (void *)&mmap_rnd_compat_bits_max, 1536 }, 1537 #endif 1538 }; 1539 #endif /* CONFIG_SYSCTL */ 1540 1541 /* 1542 * initialise the percpu counter for VM, initialise VMA state. 1543 */ 1544 void __init mmap_init(void) 1545 { 1546 int ret; 1547 1548 ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL); 1549 VM_BUG_ON(ret); 1550 #ifdef CONFIG_SYSCTL 1551 register_sysctl_init("vm", mmap_table); 1552 #endif 1553 vma_state_init(); 1554 } 1555 1556 /* 1557 * Initialise sysctl_user_reserve_kbytes. 1558 * 1559 * This is intended to prevent a user from starting a single memory hogging 1560 * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER 1561 * mode. 1562 * 1563 * The default value is min(3% of free memory, 128MB) 1564 * 128MB is enough to recover with sshd/login, bash, and top/kill. 1565 */ 1566 static int init_user_reserve(void) 1567 { 1568 unsigned long free_kbytes; 1569 1570 free_kbytes = K(global_zone_page_state(NR_FREE_PAGES)); 1571 1572 sysctl_user_reserve_kbytes = min(free_kbytes / 32, SZ_128K); 1573 return 0; 1574 } 1575 subsys_initcall(init_user_reserve); 1576 1577 /* 1578 * Initialise sysctl_admin_reserve_kbytes. 1579 * 1580 * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin 1581 * to log in and kill a memory hogging process. 1582 * 1583 * Systems with more than 256MB will reserve 8MB, enough to recover 1584 * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will 1585 * only reserve 3% of free pages by default. 1586 */ 1587 static int init_admin_reserve(void) 1588 { 1589 unsigned long free_kbytes; 1590 1591 free_kbytes = K(global_zone_page_state(NR_FREE_PAGES)); 1592 1593 sysctl_admin_reserve_kbytes = min(free_kbytes / 32, SZ_8K); 1594 return 0; 1595 } 1596 subsys_initcall(init_admin_reserve); 1597 1598 /* 1599 * Reinititalise user and admin reserves if memory is added or removed. 1600 * 1601 * The default user reserve max is 128MB, and the default max for the 1602 * admin reserve is 8MB. These are usually, but not always, enough to 1603 * enable recovery from a memory hogging process using login/sshd, a shell, 1604 * and tools like top. It may make sense to increase or even disable the 1605 * reserve depending on the existence of swap or variations in the recovery 1606 * tools. So, the admin may have changed them. 1607 * 1608 * If memory is added and the reserves have been eliminated or increased above 1609 * the default max, then we'll trust the admin. 1610 * 1611 * If memory is removed and there isn't enough free memory, then we 1612 * need to reset the reserves. 1613 * 1614 * Otherwise keep the reserve set by the admin. 1615 */ 1616 static int reserve_mem_notifier(struct notifier_block *nb, 1617 unsigned long action, void *data) 1618 { 1619 unsigned long tmp, free_kbytes; 1620 1621 switch (action) { 1622 case MEM_ONLINE: 1623 /* Default max is 128MB. Leave alone if modified by operator. */ 1624 tmp = sysctl_user_reserve_kbytes; 1625 if (tmp > 0 && tmp < SZ_128K) 1626 init_user_reserve(); 1627 1628 /* Default max is 8MB. Leave alone if modified by operator. */ 1629 tmp = sysctl_admin_reserve_kbytes; 1630 if (tmp > 0 && tmp < SZ_8K) 1631 init_admin_reserve(); 1632 1633 break; 1634 case MEM_OFFLINE: 1635 free_kbytes = K(global_zone_page_state(NR_FREE_PAGES)); 1636 1637 if (sysctl_user_reserve_kbytes > free_kbytes) { 1638 init_user_reserve(); 1639 pr_info("vm.user_reserve_kbytes reset to %lu\n", 1640 sysctl_user_reserve_kbytes); 1641 } 1642 1643 if (sysctl_admin_reserve_kbytes > free_kbytes) { 1644 init_admin_reserve(); 1645 pr_info("vm.admin_reserve_kbytes reset to %lu\n", 1646 sysctl_admin_reserve_kbytes); 1647 } 1648 break; 1649 default: 1650 break; 1651 } 1652 return NOTIFY_OK; 1653 } 1654 1655 static int __meminit init_reserve_notifier(void) 1656 { 1657 if (hotplug_memory_notifier(reserve_mem_notifier, DEFAULT_CALLBACK_PRI)) 1658 pr_err("Failed registering memory add/remove notifier for admin reserve\n"); 1659 1660 return 0; 1661 } 1662 subsys_initcall(init_reserve_notifier); 1663 1664 /* 1665 * Obtain a read lock on mm->mmap_lock, if the specified address is below the 1666 * start of the VMA, the intent is to perform a write, and it is a 1667 * downward-growing stack, then attempt to expand the stack to contain it. 1668 * 1669 * This function is intended only for obtaining an argument page from an ELF 1670 * image, and is almost certainly NOT what you want to use for any other 1671 * purpose. 1672 * 1673 * IMPORTANT - VMA fields are accessed without an mmap lock being held, so the 1674 * VMA referenced must not be linked in any user-visible tree, i.e. it must be a 1675 * new VMA being mapped. 1676 * 1677 * The function assumes that addr is either contained within the VMA or below 1678 * it, and makes no attempt to validate this value beyond that. 1679 * 1680 * Returns true if the read lock was obtained and a stack was perhaps expanded, 1681 * false if the stack expansion failed. 1682 * 1683 * On stack expansion the function temporarily acquires an mmap write lock 1684 * before downgrading it. 1685 */ 1686 bool mmap_read_lock_maybe_expand(struct mm_struct *mm, 1687 struct vm_area_struct *new_vma, 1688 unsigned long addr, bool write) 1689 { 1690 if (!write || addr >= new_vma->vm_start) { 1691 mmap_read_lock(mm); 1692 return true; 1693 } 1694 1695 if (!vma_test(new_vma, VMA_GROWSDOWN_BIT)) 1696 return false; 1697 1698 mmap_write_lock(mm); 1699 if (expand_downwards(new_vma, addr)) { 1700 mmap_write_unlock(mm); 1701 return false; 1702 } 1703 1704 mmap_write_downgrade(mm); 1705 return true; 1706 } 1707 1708 __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 1709 { 1710 struct vm_area_struct *mpnt, *tmp; 1711 int retval; 1712 unsigned long charge = 0; 1713 LIST_HEAD(uf); 1714 VMA_ITERATOR(vmi, mm, 0); 1715 1716 if (mmap_write_lock_killable(oldmm)) 1717 return -EINTR; 1718 flush_cache_dup_mm(oldmm); 1719 uprobe_dup_mmap(oldmm, mm); 1720 /* 1721 * Not linked in yet - no deadlock potential: 1722 */ 1723 mmap_write_lock_nested(mm, SINGLE_DEPTH_NESTING); 1724 1725 /* No ordering required: file already has been exposed. */ 1726 dup_mm_exe_file(mm, oldmm); 1727 1728 mm->total_vm = oldmm->total_vm; 1729 mm->data_vm = oldmm->data_vm; 1730 mm->exec_vm = oldmm->exec_vm; 1731 mm->stack_vm = oldmm->stack_vm; 1732 1733 /* Use __mt_dup() to efficiently build an identical maple tree. */ 1734 retval = __mt_dup(&oldmm->mm_mt, &mm->mm_mt, GFP_KERNEL); 1735 if (unlikely(retval)) 1736 goto out; 1737 1738 mt_clear_in_rcu(vmi.mas.tree); 1739 for_each_vma(vmi, mpnt) { 1740 struct file *file; 1741 1742 retval = vma_start_write_killable(mpnt); 1743 if (retval < 0) 1744 goto loop_out; 1745 if (vma_test(mpnt, VMA_DONTCOPY_BIT)) { 1746 retval = vma_iter_clear_gfp(&vmi, mpnt->vm_start, 1747 mpnt->vm_end, GFP_KERNEL); 1748 if (retval) 1749 goto loop_out; 1750 1751 vm_stat_account(mm, mpnt->vm_flags, -vma_pages(mpnt)); 1752 continue; 1753 } 1754 charge = 0; 1755 if (vma_test(mpnt, VMA_ACCOUNT_BIT)) { 1756 unsigned long len = vma_pages(mpnt); 1757 1758 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */ 1759 goto fail_nomem; 1760 charge = len; 1761 } 1762 1763 tmp = vm_area_dup(mpnt); 1764 if (!tmp) 1765 goto fail_nomem; 1766 retval = vma_dup_policy(mpnt, tmp); 1767 if (retval) 1768 goto fail_nomem_policy; 1769 tmp->vm_mm = mm; 1770 retval = dup_userfaultfd(tmp, &uf); 1771 if (retval) 1772 goto fail_nomem_anon_vma_fork; 1773 1774 if (vma_test(tmp, VMA_WIPEONFORK_BIT)) { 1775 /* 1776 * VMA_WIPEONFORK_BIT gets a clean slate in the child. 1777 * Don't prepare anon_vma until fault since we don't 1778 * copy page for current vma. 1779 */ 1780 tmp->anon_vma = NULL; 1781 } else if (anon_vma_fork(tmp, mpnt)) 1782 goto fail_nomem_anon_vma_fork; 1783 1784 vma_start_write(tmp); 1785 vma_clear_flags_mask(tmp, VMA_LOCKED_MASK); 1786 /* 1787 * Copy/update hugetlb private vma information. 1788 */ 1789 if (is_vm_hugetlb_page(tmp)) 1790 hugetlb_dup_vma_private(tmp); 1791 1792 /* 1793 * Link the vma into the MT. After using __mt_dup(), memory 1794 * allocation is not necessary here, so it cannot fail. 1795 */ 1796 vma_iter_bulk_store(&vmi, tmp); 1797 1798 mm->map_count++; 1799 1800 if (tmp->vm_ops && tmp->vm_ops->open) 1801 tmp->vm_ops->open(tmp); 1802 1803 file = tmp->vm_file; 1804 if (file) { 1805 struct address_space *mapping = file->f_mapping; 1806 1807 get_file(file); 1808 i_mmap_lock_write(mapping); 1809 if (vma_is_shared_maywrite(tmp)) 1810 mapping_allow_writable(mapping); 1811 flush_dcache_mmap_lock(mapping); 1812 /* insert tmp into the share list, just after mpnt */ 1813 mapping_rmap_tree_insert_after(tmp, mpnt, mapping); 1814 flush_dcache_mmap_unlock(mapping); 1815 i_mmap_unlock_write(mapping); 1816 } 1817 1818 if (!vma_test(tmp, VMA_WIPEONFORK_BIT)) 1819 retval = copy_page_range(tmp, mpnt); 1820 1821 if (retval) { 1822 mpnt = vma_next(&vmi); 1823 goto loop_out; 1824 } 1825 } 1826 /* a new mm has just been created */ 1827 retval = arch_dup_mmap(oldmm, mm); 1828 loop_out: 1829 vma_iter_free(&vmi); 1830 if (!retval) { 1831 mt_set_in_rcu(vmi.mas.tree); 1832 ksm_fork(mm, oldmm); 1833 khugepaged_fork(mm, oldmm); 1834 } else { 1835 unsigned long end; 1836 1837 /* 1838 * The entire maple tree has already been duplicated, but 1839 * replacing the vmas failed at mpnt (which could be NULL if 1840 * all were allocated but the last vma was not fully set up). 1841 * Use the start address of the failure point to clean up the 1842 * partially initialized tree. 1843 */ 1844 if (!mm->map_count) { 1845 /* zero vmas were written to the new tree. */ 1846 end = 0; 1847 } else if (mpnt) { 1848 /* partial tree failure */ 1849 end = mpnt->vm_start; 1850 } else { 1851 /* All vmas were written to the new tree */ 1852 end = ULONG_MAX; 1853 } 1854 1855 /* Hide mm from oom killer because the memory is being freed */ 1856 mm_flags_set(MMF_OOM_SKIP, mm); 1857 if (end) { 1858 vma_iter_set(&vmi, 0); 1859 tmp = vma_next(&vmi); 1860 UNMAP_STATE(unmap, &vmi, /* first = */ tmp, 1861 /* vma_start = */ 0, /* vma_end = */ end, 1862 /* prev = */ NULL, /* next = */ NULL); 1863 1864 /* 1865 * Don't iterate over vmas beyond the failure point for 1866 * both unmap_vma() and free_pgtables(). 1867 */ 1868 unmap.tree_end = end; 1869 flush_cache_mm(mm); 1870 unmap_region(&unmap); 1871 charge = tear_down_vmas(mm, &vmi, tmp, end); 1872 vm_unacct_memory(charge); 1873 } 1874 __mt_destroy(&mm->mm_mt); 1875 /* 1876 * The mm_struct is going to exit, but the locks will be dropped 1877 * first. Set the mm_struct as unstable is advisable as it is 1878 * not fully initialised. 1879 */ 1880 mm_flags_set(MMF_UNSTABLE, mm); 1881 } 1882 out: 1883 mmap_write_unlock(mm); 1884 flush_tlb_mm(oldmm); 1885 mmap_write_unlock(oldmm); 1886 if (!retval) 1887 dup_userfaultfd_complete(&uf); 1888 else 1889 dup_userfaultfd_fail(&uf); 1890 return retval; 1891 1892 fail_nomem_anon_vma_fork: 1893 mpol_put(vma_policy(tmp)); 1894 fail_nomem_policy: 1895 vm_area_free(tmp); 1896 fail_nomem: 1897 retval = -ENOMEM; 1898 vm_unacct_memory(charge); 1899 goto loop_out; 1900 } 1901