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1// SPDX-License-Identifier: GPL-2.0-only
2#include <linux/mm.h>
3#include <linux/slab.h>
4#include <linux/string.h>
5#include <linux/compiler.h>
6#include <linux/export.h>
7#include <linux/err.h>
8#include <linux/sched.h>
9#include <linux/sched/mm.h>
10#include <linux/sched/signal.h>
11#include <linux/sched/task_stack.h>
12#include <linux/security.h>
13#include <linux/swap.h>
14#include <linux/swapops.h>
15#include <linux/mman.h>
16#include <linux/hugetlb.h>
17#include <linux/vmalloc.h>
18#include <linux/userfaultfd_k.h>
19#include <linux/elf.h>
20#include <linux/elf-randomize.h>
21#include <linux/personality.h>
22#include <linux/random.h>
23#include <linux/processor.h>
24#include <linux/sizes.h>
25#include <linux/compat.h>
26
27#include <linux/uaccess.h>
28
29#include "internal.h"
30
31/**
32 * kfree_const - conditionally free memory
33 * @x: pointer to the memory
34 *
35 * Function calls kfree only if @x is not in .rodata section.
36 */
37void kfree_const(const void *x)
38{
39 if (!is_kernel_rodata((unsigned long)x))
40 kfree(x);
41}
42EXPORT_SYMBOL(kfree_const);
43
44/**
45 * kstrdup - allocate space for and copy an existing string
46 * @s: the string to duplicate
47 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
48 *
49 * Return: newly allocated copy of @s or %NULL in case of error
50 */
51char *kstrdup(const char *s, gfp_t gfp)
52{
53 size_t len;
54 char *buf;
55
56 if (!s)
57 return NULL;
58
59 len = strlen(s) + 1;
60 buf = kmalloc_track_caller(len, gfp);
61 if (buf)
62 memcpy(buf, s, len);
63 return buf;
64}
65EXPORT_SYMBOL(kstrdup);
66
67/**
68 * kstrdup_const - conditionally duplicate an existing const string
69 * @s: the string to duplicate
70 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
71 *
72 * Note: Strings allocated by kstrdup_const should be freed by kfree_const.
73 *
74 * Return: source string if it is in .rodata section otherwise
75 * fallback to kstrdup.
76 */
77const char *kstrdup_const(const char *s, gfp_t gfp)
78{
79 if (is_kernel_rodata((unsigned long)s))
80 return s;
81
82 return kstrdup(s, gfp);
83}
84EXPORT_SYMBOL(kstrdup_const);
85
86/**
87 * kstrndup - allocate space for and copy an existing string
88 * @s: the string to duplicate
89 * @max: read at most @max chars from @s
90 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
91 *
92 * Note: Use kmemdup_nul() instead if the size is known exactly.
93 *
94 * Return: newly allocated copy of @s or %NULL in case of error
95 */
96char *kstrndup(const char *s, size_t max, gfp_t gfp)
97{
98 size_t len;
99 char *buf;
100
101 if (!s)
102 return NULL;
103
104 len = strnlen(s, max);
105 buf = kmalloc_track_caller(len+1, gfp);
106 if (buf) {
107 memcpy(buf, s, len);
108 buf[len] = '\0';
109 }
110 return buf;
111}
112EXPORT_SYMBOL(kstrndup);
113
114/**
115 * kmemdup - duplicate region of memory
116 *
117 * @src: memory region to duplicate
118 * @len: memory region length
119 * @gfp: GFP mask to use
120 *
121 * Return: newly allocated copy of @src or %NULL in case of error
122 */
123void *kmemdup(const void *src, size_t len, gfp_t gfp)
124{
125 void *p;
126
127 p = kmalloc_track_caller(len, gfp);
128 if (p)
129 memcpy(p, src, len);
130 return p;
131}
132EXPORT_SYMBOL(kmemdup);
133
134/**
135 * kmemdup_nul - Create a NUL-terminated string from unterminated data
136 * @s: The data to stringify
137 * @len: The size of the data
138 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
139 *
140 * Return: newly allocated copy of @s with NUL-termination or %NULL in
141 * case of error
142 */
143char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
144{
145 char *buf;
146
147 if (!s)
148 return NULL;
149
150 buf = kmalloc_track_caller(len + 1, gfp);
151 if (buf) {
152 memcpy(buf, s, len);
153 buf[len] = '\0';
154 }
155 return buf;
156}
157EXPORT_SYMBOL(kmemdup_nul);
158
159/**
160 * memdup_user - duplicate memory region from user space
161 *
162 * @src: source address in user space
163 * @len: number of bytes to copy
164 *
165 * Return: an ERR_PTR() on failure. Result is physically
166 * contiguous, to be freed by kfree().
167 */
168void *memdup_user(const void __user *src, size_t len)
169{
170 void *p;
171
172 p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
173 if (!p)
174 return ERR_PTR(-ENOMEM);
175
176 if (copy_from_user(p, src, len)) {
177 kfree(p);
178 return ERR_PTR(-EFAULT);
179 }
180
181 return p;
182}
183EXPORT_SYMBOL(memdup_user);
184
185/**
186 * vmemdup_user - duplicate memory region from user space
187 *
188 * @src: source address in user space
189 * @len: number of bytes to copy
190 *
191 * Return: an ERR_PTR() on failure. Result may be not
192 * physically contiguous. Use kvfree() to free.
193 */
194void *vmemdup_user(const void __user *src, size_t len)
195{
196 void *p;
197
198 p = kvmalloc(len, GFP_USER);
199 if (!p)
200 return ERR_PTR(-ENOMEM);
201
202 if (copy_from_user(p, src, len)) {
203 kvfree(p);
204 return ERR_PTR(-EFAULT);
205 }
206
207 return p;
208}
209EXPORT_SYMBOL(vmemdup_user);
210
211/**
212 * strndup_user - duplicate an existing string from user space
213 * @s: The string to duplicate
214 * @n: Maximum number of bytes to copy, including the trailing NUL.
215 *
216 * Return: newly allocated copy of @s or an ERR_PTR() in case of error
217 */
218char *strndup_user(const char __user *s, long n)
219{
220 char *p;
221 long length;
222
223 length = strnlen_user(s, n);
224
225 if (!length)
226 return ERR_PTR(-EFAULT);
227
228 if (length > n)
229 return ERR_PTR(-EINVAL);
230
231 p = memdup_user(s, length);
232
233 if (IS_ERR(p))
234 return p;
235
236 p[length - 1] = '\0';
237
238 return p;
239}
240EXPORT_SYMBOL(strndup_user);
241
242/**
243 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
244 *
245 * @src: source address in user space
246 * @len: number of bytes to copy
247 *
248 * Return: an ERR_PTR() on failure.
249 */
250void *memdup_user_nul(const void __user *src, size_t len)
251{
252 char *p;
253
254 /*
255 * Always use GFP_KERNEL, since copy_from_user() can sleep and
256 * cause pagefault, which makes it pointless to use GFP_NOFS
257 * or GFP_ATOMIC.
258 */
259 p = kmalloc_track_caller(len + 1, GFP_KERNEL);
260 if (!p)
261 return ERR_PTR(-ENOMEM);
262
263 if (copy_from_user(p, src, len)) {
264 kfree(p);
265 return ERR_PTR(-EFAULT);
266 }
267 p[len] = '\0';
268
269 return p;
270}
271EXPORT_SYMBOL(memdup_user_nul);
272
273void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
274 struct vm_area_struct *prev, struct rb_node *rb_parent)
275{
276 struct vm_area_struct *next;
277
278 vma->vm_prev = prev;
279 if (prev) {
280 next = prev->vm_next;
281 prev->vm_next = vma;
282 } else {
283 mm->mmap = vma;
284 if (rb_parent)
285 next = rb_entry(rb_parent,
286 struct vm_area_struct, vm_rb);
287 else
288 next = NULL;
289 }
290 vma->vm_next = next;
291 if (next)
292 next->vm_prev = vma;
293}
294
295/* Check if the vma is being used as a stack by this task */
296int vma_is_stack_for_current(struct vm_area_struct *vma)
297{
298 struct task_struct * __maybe_unused t = current;
299
300 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
301}
302
303#ifndef STACK_RND_MASK
304#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) /* 8MB of VA */
305#endif
306
307unsigned long randomize_stack_top(unsigned long stack_top)
308{
309 unsigned long random_variable = 0;
310
311 if (current->flags & PF_RANDOMIZE) {
312 random_variable = get_random_long();
313 random_variable &= STACK_RND_MASK;
314 random_variable <<= PAGE_SHIFT;
315 }
316#ifdef CONFIG_STACK_GROWSUP
317 return PAGE_ALIGN(stack_top) + random_variable;
318#else
319 return PAGE_ALIGN(stack_top) - random_variable;
320#endif
321}
322
323#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
324unsigned long arch_randomize_brk(struct mm_struct *mm)
325{
326 /* Is the current task 32bit ? */
327 if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
328 return randomize_page(mm->brk, SZ_32M);
329
330 return randomize_page(mm->brk, SZ_1G);
331}
332
333unsigned long arch_mmap_rnd(void)
334{
335 unsigned long rnd;
336
337#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
338 if (is_compat_task())
339 rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
340 else
341#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */
342 rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
343
344 return rnd << PAGE_SHIFT;
345}
346
347static int mmap_is_legacy(struct rlimit *rlim_stack)
348{
349 if (current->personality & ADDR_COMPAT_LAYOUT)
350 return 1;
351
352 if (rlim_stack->rlim_cur == RLIM_INFINITY)
353 return 1;
354
355 return sysctl_legacy_va_layout;
356}
357
358/*
359 * Leave enough space between the mmap area and the stack to honour ulimit in
360 * the face of randomisation.
361 */
362#define MIN_GAP (SZ_128M)
363#define MAX_GAP (STACK_TOP / 6 * 5)
364
365static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
366{
367 unsigned long gap = rlim_stack->rlim_cur;
368 unsigned long pad = stack_guard_gap;
369
370 /* Account for stack randomization if necessary */
371 if (current->flags & PF_RANDOMIZE)
372 pad += (STACK_RND_MASK << PAGE_SHIFT);
373
374 /* Values close to RLIM_INFINITY can overflow. */
375 if (gap + pad > gap)
376 gap += pad;
377
378 if (gap < MIN_GAP)
379 gap = MIN_GAP;
380 else if (gap > MAX_GAP)
381 gap = MAX_GAP;
382
383 return PAGE_ALIGN(STACK_TOP - gap - rnd);
384}
385
386void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
387{
388 unsigned long random_factor = 0UL;
389
390 if (current->flags & PF_RANDOMIZE)
391 random_factor = arch_mmap_rnd();
392
393 if (mmap_is_legacy(rlim_stack)) {
394 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
395 mm->get_unmapped_area = arch_get_unmapped_area;
396 } else {
397 mm->mmap_base = mmap_base(random_factor, rlim_stack);
398 mm->get_unmapped_area = arch_get_unmapped_area_topdown;
399 }
400}
401#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
402void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
403{
404 mm->mmap_base = TASK_UNMAPPED_BASE;
405 mm->get_unmapped_area = arch_get_unmapped_area;
406}
407#endif
408
409/**
410 * __account_locked_vm - account locked pages to an mm's locked_vm
411 * @mm: mm to account against
412 * @pages: number of pages to account
413 * @inc: %true if @pages should be considered positive, %false if not
414 * @task: task used to check RLIMIT_MEMLOCK
415 * @bypass_rlim: %true if checking RLIMIT_MEMLOCK should be skipped
416 *
417 * Assumes @task and @mm are valid (i.e. at least one reference on each), and
418 * that mmap_sem is held as writer.
419 *
420 * Return:
421 * * 0 on success
422 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
423 */
424int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
425 struct task_struct *task, bool bypass_rlim)
426{
427 unsigned long locked_vm, limit;
428 int ret = 0;
429
430 lockdep_assert_held_write(&mm->mmap_sem);
431
432 locked_vm = mm->locked_vm;
433 if (inc) {
434 if (!bypass_rlim) {
435 limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
436 if (locked_vm + pages > limit)
437 ret = -ENOMEM;
438 }
439 if (!ret)
440 mm->locked_vm = locked_vm + pages;
441 } else {
442 WARN_ON_ONCE(pages > locked_vm);
443 mm->locked_vm = locked_vm - pages;
444 }
445
446 pr_debug("%s: [%d] caller %ps %c%lu %lu/%lu%s\n", __func__, task->pid,
447 (void *)_RET_IP_, (inc) ? '+' : '-', pages << PAGE_SHIFT,
448 locked_vm << PAGE_SHIFT, task_rlimit(task, RLIMIT_MEMLOCK),
449 ret ? " - exceeded" : "");
450
451 return ret;
452}
453EXPORT_SYMBOL_GPL(__account_locked_vm);
454
455/**
456 * account_locked_vm - account locked pages to an mm's locked_vm
457 * @mm: mm to account against, may be NULL
458 * @pages: number of pages to account
459 * @inc: %true if @pages should be considered positive, %false if not
460 *
461 * Assumes a non-NULL @mm is valid (i.e. at least one reference on it).
462 *
463 * Return:
464 * * 0 on success, or if mm is NULL
465 * * -ENOMEM if RLIMIT_MEMLOCK would be exceeded.
466 */
467int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc)
468{
469 int ret;
470
471 if (pages == 0 || !mm)
472 return 0;
473
474 down_write(&mm->mmap_sem);
475 ret = __account_locked_vm(mm, pages, inc, current,
476 capable(CAP_IPC_LOCK));
477 up_write(&mm->mmap_sem);
478
479 return ret;
480}
481EXPORT_SYMBOL_GPL(account_locked_vm);
482
483unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
484 unsigned long len, unsigned long prot,
485 unsigned long flag, unsigned long pgoff)
486{
487 unsigned long ret;
488 struct mm_struct *mm = current->mm;
489 unsigned long populate;
490 LIST_HEAD(uf);
491
492 ret = security_mmap_file(file, prot, flag);
493 if (!ret) {
494 if (down_write_killable(&mm->mmap_sem))
495 return -EINTR;
496 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
497 &populate, &uf);
498 up_write(&mm->mmap_sem);
499 userfaultfd_unmap_complete(mm, &uf);
500 if (populate)
501 mm_populate(ret, populate);
502 }
503 return ret;
504}
505
506unsigned long vm_mmap(struct file *file, unsigned long addr,
507 unsigned long len, unsigned long prot,
508 unsigned long flag, unsigned long offset)
509{
510 if (unlikely(offset + PAGE_ALIGN(len) < offset))
511 return -EINVAL;
512 if (unlikely(offset_in_page(offset)))
513 return -EINVAL;
514
515 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
516}
517EXPORT_SYMBOL(vm_mmap);
518
519/**
520 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
521 * failure, fall back to non-contiguous (vmalloc) allocation.
522 * @size: size of the request.
523 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
524 * @node: numa node to allocate from
525 *
526 * Uses kmalloc to get the memory but if the allocation fails then falls back
527 * to the vmalloc allocator. Use kvfree for freeing the memory.
528 *
529 * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
530 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
531 * preferable to the vmalloc fallback, due to visible performance drawbacks.
532 *
533 * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not
534 * fall back to vmalloc.
535 *
536 * Return: pointer to the allocated memory of %NULL in case of failure
537 */
538void *kvmalloc_node(size_t size, gfp_t flags, int node)
539{
540 gfp_t kmalloc_flags = flags;
541 void *ret;
542
543 /*
544 * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
545 * so the given set of flags has to be compatible.
546 */
547 if ((flags & GFP_KERNEL) != GFP_KERNEL)
548 return kmalloc_node(size, flags, node);
549
550 /*
551 * We want to attempt a large physically contiguous block first because
552 * it is less likely to fragment multiple larger blocks and therefore
553 * contribute to a long term fragmentation less than vmalloc fallback.
554 * However make sure that larger requests are not too disruptive - no
555 * OOM killer and no allocation failure warnings as we have a fallback.
556 */
557 if (size > PAGE_SIZE) {
558 kmalloc_flags |= __GFP_NOWARN;
559
560 if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
561 kmalloc_flags |= __GFP_NORETRY;
562 }
563
564 ret = kmalloc_node(size, kmalloc_flags, node);
565
566 /*
567 * It doesn't really make sense to fallback to vmalloc for sub page
568 * requests
569 */
570 if (ret || size <= PAGE_SIZE)
571 return ret;
572
573 return __vmalloc_node_flags_caller(size, node, flags,
574 __builtin_return_address(0));
575}
576EXPORT_SYMBOL(kvmalloc_node);
577
578/**
579 * kvfree() - Free memory.
580 * @addr: Pointer to allocated memory.
581 *
582 * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
583 * It is slightly more efficient to use kfree() or vfree() if you are certain
584 * that you know which one to use.
585 *
586 * Context: Either preemptible task context or not-NMI interrupt.
587 */
588void kvfree(const void *addr)
589{
590 if (is_vmalloc_addr(addr))
591 vfree(addr);
592 else
593 kfree(addr);
594}
595EXPORT_SYMBOL(kvfree);
596
597static inline void *__page_rmapping(struct page *page)
598{
599 unsigned long mapping;
600
601 mapping = (unsigned long)page->mapping;
602 mapping &= ~PAGE_MAPPING_FLAGS;
603
604 return (void *)mapping;
605}
606
607/* Neutral page->mapping pointer to address_space or anon_vma or other */
608void *page_rmapping(struct page *page)
609{
610 page = compound_head(page);
611 return __page_rmapping(page);
612}
613
614/*
615 * Return true if this page is mapped into pagetables.
616 * For compound page it returns true if any subpage of compound page is mapped.
617 */
618bool page_mapped(struct page *page)
619{
620 int i;
621
622 if (likely(!PageCompound(page)))
623 return atomic_read(&page->_mapcount) >= 0;
624 page = compound_head(page);
625 if (atomic_read(compound_mapcount_ptr(page)) >= 0)
626 return true;
627 if (PageHuge(page))
628 return false;
629 for (i = 0; i < compound_nr(page); i++) {
630 if (atomic_read(&page[i]._mapcount) >= 0)
631 return true;
632 }
633 return false;
634}
635EXPORT_SYMBOL(page_mapped);
636
637struct anon_vma *page_anon_vma(struct page *page)
638{
639 unsigned long mapping;
640
641 page = compound_head(page);
642 mapping = (unsigned long)page->mapping;
643 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
644 return NULL;
645 return __page_rmapping(page);
646}
647
648struct address_space *page_mapping(struct page *page)
649{
650 struct address_space *mapping;
651
652 page = compound_head(page);
653
654 /* This happens if someone calls flush_dcache_page on slab page */
655 if (unlikely(PageSlab(page)))
656 return NULL;
657
658 if (unlikely(PageSwapCache(page))) {
659 swp_entry_t entry;
660
661 entry.val = page_private(page);
662 return swap_address_space(entry);
663 }
664
665 mapping = page->mapping;
666 if ((unsigned long)mapping & PAGE_MAPPING_ANON)
667 return NULL;
668
669 return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
670}
671EXPORT_SYMBOL(page_mapping);
672
673/*
674 * For file cache pages, return the address_space, otherwise return NULL
675 */
676struct address_space *page_mapping_file(struct page *page)
677{
678 if (unlikely(PageSwapCache(page)))
679 return NULL;
680 return page_mapping(page);
681}
682
683/* Slow path of page_mapcount() for compound pages */
684int __page_mapcount(struct page *page)
685{
686 int ret;
687
688 ret = atomic_read(&page->_mapcount) + 1;
689 /*
690 * For file THP page->_mapcount contains total number of mapping
691 * of the page: no need to look into compound_mapcount.
692 */
693 if (!PageAnon(page) && !PageHuge(page))
694 return ret;
695 page = compound_head(page);
696 ret += atomic_read(compound_mapcount_ptr(page)) + 1;
697 if (PageDoubleMap(page))
698 ret--;
699 return ret;
700}
701EXPORT_SYMBOL_GPL(__page_mapcount);
702
703int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
704int sysctl_overcommit_ratio __read_mostly = 50;
705unsigned long sysctl_overcommit_kbytes __read_mostly;
706int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
707unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
708unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
709
710int overcommit_ratio_handler(struct ctl_table *table, int write,
711 void __user *buffer, size_t *lenp,
712 loff_t *ppos)
713{
714 int ret;
715
716 ret = proc_dointvec(table, write, buffer, lenp, ppos);
717 if (ret == 0 && write)
718 sysctl_overcommit_kbytes = 0;
719 return ret;
720}
721
722int overcommit_kbytes_handler(struct ctl_table *table, int write,
723 void __user *buffer, size_t *lenp,
724 loff_t *ppos)
725{
726 int ret;
727
728 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
729 if (ret == 0 && write)
730 sysctl_overcommit_ratio = 0;
731 return ret;
732}
733
734/*
735 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
736 */
737unsigned long vm_commit_limit(void)
738{
739 unsigned long allowed;
740
741 if (sysctl_overcommit_kbytes)
742 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
743 else
744 allowed = ((totalram_pages() - hugetlb_total_pages())
745 * sysctl_overcommit_ratio / 100);
746 allowed += total_swap_pages;
747
748 return allowed;
749}
750
751/*
752 * Make sure vm_committed_as in one cacheline and not cacheline shared with
753 * other variables. It can be updated by several CPUs frequently.
754 */
755struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
756
757/*
758 * The global memory commitment made in the system can be a metric
759 * that can be used to drive ballooning decisions when Linux is hosted
760 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
761 * balancing memory across competing virtual machines that are hosted.
762 * Several metrics drive this policy engine including the guest reported
763 * memory commitment.
764 */
765unsigned long vm_memory_committed(void)
766{
767 return percpu_counter_read_positive(&vm_committed_as);
768}
769EXPORT_SYMBOL_GPL(vm_memory_committed);
770
771/*
772 * Check that a process has enough memory to allocate a new virtual
773 * mapping. 0 means there is enough memory for the allocation to
774 * succeed and -ENOMEM implies there is not.
775 *
776 * We currently support three overcommit policies, which are set via the
777 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting.rst
778 *
779 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
780 * Additional code 2002 Jul 20 by Robert Love.
781 *
782 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
783 *
784 * Note this is a helper function intended to be used by LSMs which
785 * wish to use this logic.
786 */
787int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
788{
789 long allowed;
790
791 VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
792 -(s64)vm_committed_as_batch * num_online_cpus(),
793 "memory commitment underflow");
794
795 vm_acct_memory(pages);
796
797 /*
798 * Sometimes we want to use more memory than we have
799 */
800 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
801 return 0;
802
803 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
804 if (pages > totalram_pages() + total_swap_pages)
805 goto error;
806 return 0;
807 }
808
809 allowed = vm_commit_limit();
810 /*
811 * Reserve some for root
812 */
813 if (!cap_sys_admin)
814 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
815
816 /*
817 * Don't let a single process grow so big a user can't recover
818 */
819 if (mm) {
820 long reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
821
822 allowed -= min_t(long, mm->total_vm / 32, reserve);
823 }
824
825 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
826 return 0;
827error:
828 vm_unacct_memory(pages);
829
830 return -ENOMEM;
831}
832
833/**
834 * get_cmdline() - copy the cmdline value to a buffer.
835 * @task: the task whose cmdline value to copy.
836 * @buffer: the buffer to copy to.
837 * @buflen: the length of the buffer. Larger cmdline values are truncated
838 * to this length.
839 *
840 * Return: the size of the cmdline field copied. Note that the copy does
841 * not guarantee an ending NULL byte.
842 */
843int get_cmdline(struct task_struct *task, char *buffer, int buflen)
844{
845 int res = 0;
846 unsigned int len;
847 struct mm_struct *mm = get_task_mm(task);
848 unsigned long arg_start, arg_end, env_start, env_end;
849 if (!mm)
850 goto out;
851 if (!mm->arg_end)
852 goto out_mm; /* Shh! No looking before we're done */
853
854 spin_lock(&mm->arg_lock);
855 arg_start = mm->arg_start;
856 arg_end = mm->arg_end;
857 env_start = mm->env_start;
858 env_end = mm->env_end;
859 spin_unlock(&mm->arg_lock);
860
861 len = arg_end - arg_start;
862
863 if (len > buflen)
864 len = buflen;
865
866 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
867
868 /*
869 * If the nul at the end of args has been overwritten, then
870 * assume application is using setproctitle(3).
871 */
872 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
873 len = strnlen(buffer, res);
874 if (len < res) {
875 res = len;
876 } else {
877 len = env_end - env_start;
878 if (len > buflen - res)
879 len = buflen - res;
880 res += access_process_vm(task, env_start,
881 buffer+res, len,
882 FOLL_FORCE);
883 res = strnlen(buffer, res);
884 }
885 }
886out_mm:
887 mmput(mm);
888out:
889 return res;
890}
891
892int memcmp_pages(struct page *page1, struct page *page2)
893{
894 char *addr1, *addr2;
895 int ret;
896
897 addr1 = kmap_atomic(page1);
898 addr2 = kmap_atomic(page2);
899 ret = memcmp(addr1, addr2, PAGE_SIZE);
900 kunmap_atomic(addr2);
901 kunmap_atomic(addr1);
902 return ret;
903}
1#include <linux/mm.h>
2#include <linux/slab.h>
3#include <linux/string.h>
4#include <linux/compiler.h>
5#include <linux/export.h>
6#include <linux/err.h>
7#include <linux/sched.h>
8#include <linux/sched/mm.h>
9#include <linux/sched/task_stack.h>
10#include <linux/security.h>
11#include <linux/swap.h>
12#include <linux/swapops.h>
13#include <linux/mman.h>
14#include <linux/hugetlb.h>
15#include <linux/vmalloc.h>
16#include <linux/userfaultfd_k.h>
17
18#include <asm/sections.h>
19#include <linux/uaccess.h>
20
21#include "internal.h"
22
23static inline int is_kernel_rodata(unsigned long addr)
24{
25 return addr >= (unsigned long)__start_rodata &&
26 addr < (unsigned long)__end_rodata;
27}
28
29/**
30 * kfree_const - conditionally free memory
31 * @x: pointer to the memory
32 *
33 * Function calls kfree only if @x is not in .rodata section.
34 */
35void kfree_const(const void *x)
36{
37 if (!is_kernel_rodata((unsigned long)x))
38 kfree(x);
39}
40EXPORT_SYMBOL(kfree_const);
41
42/**
43 * kstrdup - allocate space for and copy an existing string
44 * @s: the string to duplicate
45 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
46 */
47char *kstrdup(const char *s, gfp_t gfp)
48{
49 size_t len;
50 char *buf;
51
52 if (!s)
53 return NULL;
54
55 len = strlen(s) + 1;
56 buf = kmalloc_track_caller(len, gfp);
57 if (buf)
58 memcpy(buf, s, len);
59 return buf;
60}
61EXPORT_SYMBOL(kstrdup);
62
63/**
64 * kstrdup_const - conditionally duplicate an existing const string
65 * @s: the string to duplicate
66 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
67 *
68 * Function returns source string if it is in .rodata section otherwise it
69 * fallbacks to kstrdup.
70 * Strings allocated by kstrdup_const should be freed by kfree_const.
71 */
72const char *kstrdup_const(const char *s, gfp_t gfp)
73{
74 if (is_kernel_rodata((unsigned long)s))
75 return s;
76
77 return kstrdup(s, gfp);
78}
79EXPORT_SYMBOL(kstrdup_const);
80
81/**
82 * kstrndup - allocate space for and copy an existing string
83 * @s: the string to duplicate
84 * @max: read at most @max chars from @s
85 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
86 *
87 * Note: Use kmemdup_nul() instead if the size is known exactly.
88 */
89char *kstrndup(const char *s, size_t max, gfp_t gfp)
90{
91 size_t len;
92 char *buf;
93
94 if (!s)
95 return NULL;
96
97 len = strnlen(s, max);
98 buf = kmalloc_track_caller(len+1, gfp);
99 if (buf) {
100 memcpy(buf, s, len);
101 buf[len] = '\0';
102 }
103 return buf;
104}
105EXPORT_SYMBOL(kstrndup);
106
107/**
108 * kmemdup - duplicate region of memory
109 *
110 * @src: memory region to duplicate
111 * @len: memory region length
112 * @gfp: GFP mask to use
113 */
114void *kmemdup(const void *src, size_t len, gfp_t gfp)
115{
116 void *p;
117
118 p = kmalloc_track_caller(len, gfp);
119 if (p)
120 memcpy(p, src, len);
121 return p;
122}
123EXPORT_SYMBOL(kmemdup);
124
125/**
126 * kmemdup_nul - Create a NUL-terminated string from unterminated data
127 * @s: The data to stringify
128 * @len: The size of the data
129 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
130 */
131char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
132{
133 char *buf;
134
135 if (!s)
136 return NULL;
137
138 buf = kmalloc_track_caller(len + 1, gfp);
139 if (buf) {
140 memcpy(buf, s, len);
141 buf[len] = '\0';
142 }
143 return buf;
144}
145EXPORT_SYMBOL(kmemdup_nul);
146
147/**
148 * memdup_user - duplicate memory region from user space
149 *
150 * @src: source address in user space
151 * @len: number of bytes to copy
152 *
153 * Returns an ERR_PTR() on failure. Result is physically
154 * contiguous, to be freed by kfree().
155 */
156void *memdup_user(const void __user *src, size_t len)
157{
158 void *p;
159
160 p = kmalloc_track_caller(len, GFP_USER);
161 if (!p)
162 return ERR_PTR(-ENOMEM);
163
164 if (copy_from_user(p, src, len)) {
165 kfree(p);
166 return ERR_PTR(-EFAULT);
167 }
168
169 return p;
170}
171EXPORT_SYMBOL(memdup_user);
172
173/**
174 * vmemdup_user - duplicate memory region from user space
175 *
176 * @src: source address in user space
177 * @len: number of bytes to copy
178 *
179 * Returns an ERR_PTR() on failure. Result may be not
180 * physically contiguous. Use kvfree() to free.
181 */
182void *vmemdup_user(const void __user *src, size_t len)
183{
184 void *p;
185
186 p = kvmalloc(len, GFP_USER);
187 if (!p)
188 return ERR_PTR(-ENOMEM);
189
190 if (copy_from_user(p, src, len)) {
191 kvfree(p);
192 return ERR_PTR(-EFAULT);
193 }
194
195 return p;
196}
197EXPORT_SYMBOL(vmemdup_user);
198
199/*
200 * strndup_user - duplicate an existing string from user space
201 * @s: The string to duplicate
202 * @n: Maximum number of bytes to copy, including the trailing NUL.
203 */
204char *strndup_user(const char __user *s, long n)
205{
206 char *p;
207 long length;
208
209 length = strnlen_user(s, n);
210
211 if (!length)
212 return ERR_PTR(-EFAULT);
213
214 if (length > n)
215 return ERR_PTR(-EINVAL);
216
217 p = memdup_user(s, length);
218
219 if (IS_ERR(p))
220 return p;
221
222 p[length - 1] = '\0';
223
224 return p;
225}
226EXPORT_SYMBOL(strndup_user);
227
228/**
229 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
230 *
231 * @src: source address in user space
232 * @len: number of bytes to copy
233 *
234 * Returns an ERR_PTR() on failure.
235 */
236void *memdup_user_nul(const void __user *src, size_t len)
237{
238 char *p;
239
240 /*
241 * Always use GFP_KERNEL, since copy_from_user() can sleep and
242 * cause pagefault, which makes it pointless to use GFP_NOFS
243 * or GFP_ATOMIC.
244 */
245 p = kmalloc_track_caller(len + 1, GFP_KERNEL);
246 if (!p)
247 return ERR_PTR(-ENOMEM);
248
249 if (copy_from_user(p, src, len)) {
250 kfree(p);
251 return ERR_PTR(-EFAULT);
252 }
253 p[len] = '\0';
254
255 return p;
256}
257EXPORT_SYMBOL(memdup_user_nul);
258
259void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
260 struct vm_area_struct *prev, struct rb_node *rb_parent)
261{
262 struct vm_area_struct *next;
263
264 vma->vm_prev = prev;
265 if (prev) {
266 next = prev->vm_next;
267 prev->vm_next = vma;
268 } else {
269 mm->mmap = vma;
270 if (rb_parent)
271 next = rb_entry(rb_parent,
272 struct vm_area_struct, vm_rb);
273 else
274 next = NULL;
275 }
276 vma->vm_next = next;
277 if (next)
278 next->vm_prev = vma;
279}
280
281/* Check if the vma is being used as a stack by this task */
282int vma_is_stack_for_current(struct vm_area_struct *vma)
283{
284 struct task_struct * __maybe_unused t = current;
285
286 return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
287}
288
289#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
290void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
291{
292 mm->mmap_base = TASK_UNMAPPED_BASE;
293 mm->get_unmapped_area = arch_get_unmapped_area;
294}
295#endif
296
297/*
298 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
299 * back to the regular GUP.
300 * Note a difference with get_user_pages_fast: this always returns the
301 * number of pages pinned, 0 if no pages were pinned.
302 * If the architecture does not support this function, simply return with no
303 * pages pinned.
304 */
305int __weak __get_user_pages_fast(unsigned long start,
306 int nr_pages, int write, struct page **pages)
307{
308 return 0;
309}
310EXPORT_SYMBOL_GPL(__get_user_pages_fast);
311
312/**
313 * get_user_pages_fast() - pin user pages in memory
314 * @start: starting user address
315 * @nr_pages: number of pages from start to pin
316 * @write: whether pages will be written to
317 * @pages: array that receives pointers to the pages pinned.
318 * Should be at least nr_pages long.
319 *
320 * Returns number of pages pinned. This may be fewer than the number
321 * requested. If nr_pages is 0 or negative, returns 0. If no pages
322 * were pinned, returns -errno.
323 *
324 * get_user_pages_fast provides equivalent functionality to get_user_pages,
325 * operating on current and current->mm, with force=0 and vma=NULL. However
326 * unlike get_user_pages, it must be called without mmap_sem held.
327 *
328 * get_user_pages_fast may take mmap_sem and page table locks, so no
329 * assumptions can be made about lack of locking. get_user_pages_fast is to be
330 * implemented in a way that is advantageous (vs get_user_pages()) when the
331 * user memory area is already faulted in and present in ptes. However if the
332 * pages have to be faulted in, it may turn out to be slightly slower so
333 * callers need to carefully consider what to use. On many architectures,
334 * get_user_pages_fast simply falls back to get_user_pages.
335 */
336int __weak get_user_pages_fast(unsigned long start,
337 int nr_pages, int write, struct page **pages)
338{
339 return get_user_pages_unlocked(start, nr_pages, pages,
340 write ? FOLL_WRITE : 0);
341}
342EXPORT_SYMBOL_GPL(get_user_pages_fast);
343
344unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
345 unsigned long len, unsigned long prot,
346 unsigned long flag, unsigned long pgoff)
347{
348 unsigned long ret;
349 struct mm_struct *mm = current->mm;
350 unsigned long populate;
351 LIST_HEAD(uf);
352
353 ret = security_mmap_file(file, prot, flag);
354 if (!ret) {
355 if (down_write_killable(&mm->mmap_sem))
356 return -EINTR;
357 ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
358 &populate, &uf);
359 up_write(&mm->mmap_sem);
360 userfaultfd_unmap_complete(mm, &uf);
361 if (populate)
362 mm_populate(ret, populate);
363 }
364 return ret;
365}
366
367unsigned long vm_mmap(struct file *file, unsigned long addr,
368 unsigned long len, unsigned long prot,
369 unsigned long flag, unsigned long offset)
370{
371 if (unlikely(offset + PAGE_ALIGN(len) < offset))
372 return -EINVAL;
373 if (unlikely(offset_in_page(offset)))
374 return -EINVAL;
375
376 return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
377}
378EXPORT_SYMBOL(vm_mmap);
379
380/**
381 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
382 * failure, fall back to non-contiguous (vmalloc) allocation.
383 * @size: size of the request.
384 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
385 * @node: numa node to allocate from
386 *
387 * Uses kmalloc to get the memory but if the allocation fails then falls back
388 * to the vmalloc allocator. Use kvfree for freeing the memory.
389 *
390 * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
391 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
392 * preferable to the vmalloc fallback, due to visible performance drawbacks.
393 *
394 * Any use of gfp flags outside of GFP_KERNEL should be consulted with mm people.
395 */
396void *kvmalloc_node(size_t size, gfp_t flags, int node)
397{
398 gfp_t kmalloc_flags = flags;
399 void *ret;
400
401 /*
402 * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
403 * so the given set of flags has to be compatible.
404 */
405 WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL);
406
407 /*
408 * We want to attempt a large physically contiguous block first because
409 * it is less likely to fragment multiple larger blocks and therefore
410 * contribute to a long term fragmentation less than vmalloc fallback.
411 * However make sure that larger requests are not too disruptive - no
412 * OOM killer and no allocation failure warnings as we have a fallback.
413 */
414 if (size > PAGE_SIZE) {
415 kmalloc_flags |= __GFP_NOWARN;
416
417 if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
418 kmalloc_flags |= __GFP_NORETRY;
419 }
420
421 ret = kmalloc_node(size, kmalloc_flags, node);
422
423 /*
424 * It doesn't really make sense to fallback to vmalloc for sub page
425 * requests
426 */
427 if (ret || size <= PAGE_SIZE)
428 return ret;
429
430 return __vmalloc_node_flags_caller(size, node, flags,
431 __builtin_return_address(0));
432}
433EXPORT_SYMBOL(kvmalloc_node);
434
435void kvfree(const void *addr)
436{
437 if (is_vmalloc_addr(addr))
438 vfree(addr);
439 else
440 kfree(addr);
441}
442EXPORT_SYMBOL(kvfree);
443
444static inline void *__page_rmapping(struct page *page)
445{
446 unsigned long mapping;
447
448 mapping = (unsigned long)page->mapping;
449 mapping &= ~PAGE_MAPPING_FLAGS;
450
451 return (void *)mapping;
452}
453
454/* Neutral page->mapping pointer to address_space or anon_vma or other */
455void *page_rmapping(struct page *page)
456{
457 page = compound_head(page);
458 return __page_rmapping(page);
459}
460
461/*
462 * Return true if this page is mapped into pagetables.
463 * For compound page it returns true if any subpage of compound page is mapped.
464 */
465bool page_mapped(struct page *page)
466{
467 int i;
468
469 if (likely(!PageCompound(page)))
470 return atomic_read(&page->_mapcount) >= 0;
471 page = compound_head(page);
472 if (atomic_read(compound_mapcount_ptr(page)) >= 0)
473 return true;
474 if (PageHuge(page))
475 return false;
476 for (i = 0; i < hpage_nr_pages(page); i++) {
477 if (atomic_read(&page[i]._mapcount) >= 0)
478 return true;
479 }
480 return false;
481}
482EXPORT_SYMBOL(page_mapped);
483
484struct anon_vma *page_anon_vma(struct page *page)
485{
486 unsigned long mapping;
487
488 page = compound_head(page);
489 mapping = (unsigned long)page->mapping;
490 if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
491 return NULL;
492 return __page_rmapping(page);
493}
494
495struct address_space *page_mapping(struct page *page)
496{
497 struct address_space *mapping;
498
499 page = compound_head(page);
500
501 /* This happens if someone calls flush_dcache_page on slab page */
502 if (unlikely(PageSlab(page)))
503 return NULL;
504
505 if (unlikely(PageSwapCache(page))) {
506 swp_entry_t entry;
507
508 entry.val = page_private(page);
509 return swap_address_space(entry);
510 }
511
512 mapping = page->mapping;
513 if ((unsigned long)mapping & PAGE_MAPPING_ANON)
514 return NULL;
515
516 return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
517}
518EXPORT_SYMBOL(page_mapping);
519
520/*
521 * For file cache pages, return the address_space, otherwise return NULL
522 */
523struct address_space *page_mapping_file(struct page *page)
524{
525 if (unlikely(PageSwapCache(page)))
526 return NULL;
527 return page_mapping(page);
528}
529
530/* Slow path of page_mapcount() for compound pages */
531int __page_mapcount(struct page *page)
532{
533 int ret;
534
535 ret = atomic_read(&page->_mapcount) + 1;
536 /*
537 * For file THP page->_mapcount contains total number of mapping
538 * of the page: no need to look into compound_mapcount.
539 */
540 if (!PageAnon(page) && !PageHuge(page))
541 return ret;
542 page = compound_head(page);
543 ret += atomic_read(compound_mapcount_ptr(page)) + 1;
544 if (PageDoubleMap(page))
545 ret--;
546 return ret;
547}
548EXPORT_SYMBOL_GPL(__page_mapcount);
549
550int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
551int sysctl_overcommit_ratio __read_mostly = 50;
552unsigned long sysctl_overcommit_kbytes __read_mostly;
553int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
554unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
555unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
556
557int overcommit_ratio_handler(struct ctl_table *table, int write,
558 void __user *buffer, size_t *lenp,
559 loff_t *ppos)
560{
561 int ret;
562
563 ret = proc_dointvec(table, write, buffer, lenp, ppos);
564 if (ret == 0 && write)
565 sysctl_overcommit_kbytes = 0;
566 return ret;
567}
568
569int overcommit_kbytes_handler(struct ctl_table *table, int write,
570 void __user *buffer, size_t *lenp,
571 loff_t *ppos)
572{
573 int ret;
574
575 ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
576 if (ret == 0 && write)
577 sysctl_overcommit_ratio = 0;
578 return ret;
579}
580
581/*
582 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
583 */
584unsigned long vm_commit_limit(void)
585{
586 unsigned long allowed;
587
588 if (sysctl_overcommit_kbytes)
589 allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
590 else
591 allowed = ((totalram_pages - hugetlb_total_pages())
592 * sysctl_overcommit_ratio / 100);
593 allowed += total_swap_pages;
594
595 return allowed;
596}
597
598/*
599 * Make sure vm_committed_as in one cacheline and not cacheline shared with
600 * other variables. It can be updated by several CPUs frequently.
601 */
602struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
603
604/*
605 * The global memory commitment made in the system can be a metric
606 * that can be used to drive ballooning decisions when Linux is hosted
607 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
608 * balancing memory across competing virtual machines that are hosted.
609 * Several metrics drive this policy engine including the guest reported
610 * memory commitment.
611 */
612unsigned long vm_memory_committed(void)
613{
614 return percpu_counter_read_positive(&vm_committed_as);
615}
616EXPORT_SYMBOL_GPL(vm_memory_committed);
617
618/*
619 * Check that a process has enough memory to allocate a new virtual
620 * mapping. 0 means there is enough memory for the allocation to
621 * succeed and -ENOMEM implies there is not.
622 *
623 * We currently support three overcommit policies, which are set via the
624 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
625 *
626 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
627 * Additional code 2002 Jul 20 by Robert Love.
628 *
629 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
630 *
631 * Note this is a helper function intended to be used by LSMs which
632 * wish to use this logic.
633 */
634int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
635{
636 long free, allowed, reserve;
637
638 VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
639 -(s64)vm_committed_as_batch * num_online_cpus(),
640 "memory commitment underflow");
641
642 vm_acct_memory(pages);
643
644 /*
645 * Sometimes we want to use more memory than we have
646 */
647 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
648 return 0;
649
650 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
651 free = global_zone_page_state(NR_FREE_PAGES);
652 free += global_node_page_state(NR_FILE_PAGES);
653
654 /*
655 * shmem pages shouldn't be counted as free in this
656 * case, they can't be purged, only swapped out, and
657 * that won't affect the overall amount of available
658 * memory in the system.
659 */
660 free -= global_node_page_state(NR_SHMEM);
661
662 free += get_nr_swap_pages();
663
664 /*
665 * Any slabs which are created with the
666 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
667 * which are reclaimable, under pressure. The dentry
668 * cache and most inode caches should fall into this
669 */
670 free += global_node_page_state(NR_SLAB_RECLAIMABLE);
671
672 /*
673 * Part of the kernel memory, which can be released
674 * under memory pressure.
675 */
676 free += global_node_page_state(
677 NR_INDIRECTLY_RECLAIMABLE_BYTES) >> PAGE_SHIFT;
678
679 /*
680 * Leave reserved pages. The pages are not for anonymous pages.
681 */
682 if (free <= totalreserve_pages)
683 goto error;
684 else
685 free -= totalreserve_pages;
686
687 /*
688 * Reserve some for root
689 */
690 if (!cap_sys_admin)
691 free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
692
693 if (free > pages)
694 return 0;
695
696 goto error;
697 }
698
699 allowed = vm_commit_limit();
700 /*
701 * Reserve some for root
702 */
703 if (!cap_sys_admin)
704 allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
705
706 /*
707 * Don't let a single process grow so big a user can't recover
708 */
709 if (mm) {
710 reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
711 allowed -= min_t(long, mm->total_vm / 32, reserve);
712 }
713
714 if (percpu_counter_read_positive(&vm_committed_as) < allowed)
715 return 0;
716error:
717 vm_unacct_memory(pages);
718
719 return -ENOMEM;
720}
721
722/**
723 * get_cmdline() - copy the cmdline value to a buffer.
724 * @task: the task whose cmdline value to copy.
725 * @buffer: the buffer to copy to.
726 * @buflen: the length of the buffer. Larger cmdline values are truncated
727 * to this length.
728 * Returns the size of the cmdline field copied. Note that the copy does
729 * not guarantee an ending NULL byte.
730 */
731int get_cmdline(struct task_struct *task, char *buffer, int buflen)
732{
733 int res = 0;
734 unsigned int len;
735 struct mm_struct *mm = get_task_mm(task);
736 unsigned long arg_start, arg_end, env_start, env_end;
737 if (!mm)
738 goto out;
739 if (!mm->arg_end)
740 goto out_mm; /* Shh! No looking before we're done */
741
742 down_read(&mm->mmap_sem);
743 arg_start = mm->arg_start;
744 arg_end = mm->arg_end;
745 env_start = mm->env_start;
746 env_end = mm->env_end;
747 up_read(&mm->mmap_sem);
748
749 len = arg_end - arg_start;
750
751 if (len > buflen)
752 len = buflen;
753
754 res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
755
756 /*
757 * If the nul at the end of args has been overwritten, then
758 * assume application is using setproctitle(3).
759 */
760 if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
761 len = strnlen(buffer, res);
762 if (len < res) {
763 res = len;
764 } else {
765 len = env_end - env_start;
766 if (len > buflen - res)
767 len = buflen - res;
768 res += access_process_vm(task, env_start,
769 buffer+res, len,
770 FOLL_FORCE);
771 res = strnlen(buffer, res);
772 }
773 }
774out_mm:
775 mmput(mm);
776out:
777 return res;
778}