util.c 19.5 KB
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#include <linux/mm.h>
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#include <linux/slab.h>
#include <linux/string.h>
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#include <linux/compiler.h>
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#include <linux/export.h>
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#include <linux/err.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/sched/task_stack.h>
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#include <linux/security.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/mman.h>
#include <linux/hugetlb.h>
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#include <linux/vmalloc.h>
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#include <linux/userfaultfd_k.h>
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#include <linux/uaccess.h>
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#include "internal.h"

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/**
 * kfree_const - conditionally free memory
 * @x: pointer to the memory
 *
 * Function calls kfree only if @x is not in .rodata section.
 */
void kfree_const(const void *x)
{
	if (!is_kernel_rodata((unsigned long)x))
		kfree(x);
}
EXPORT_SYMBOL(kfree_const);

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/**
 * kstrdup - allocate space for and copy an existing string
 * @s: the string to duplicate
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 */
char *kstrdup(const char *s, gfp_t gfp)
{
	size_t len;
	char *buf;

	if (!s)
		return NULL;

	len = strlen(s) + 1;
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	buf = kmalloc_track_caller(len, gfp);
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	if (buf)
		memcpy(buf, s, len);
	return buf;
}
EXPORT_SYMBOL(kstrdup);
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/**
 * kstrdup_const - conditionally duplicate an existing const string
 * @s: the string to duplicate
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 *
 * Function returns source string if it is in .rodata section otherwise it
 * fallbacks to kstrdup.
 * Strings allocated by kstrdup_const should be freed by kfree_const.
 */
const char *kstrdup_const(const char *s, gfp_t gfp)
{
	if (is_kernel_rodata((unsigned long)s))
		return s;

	return kstrdup(s, gfp);
}
EXPORT_SYMBOL(kstrdup_const);

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/**
 * kstrndup - allocate space for and copy an existing string
 * @s: the string to duplicate
 * @max: read at most @max chars from @s
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
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 *
 * Note: Use kmemdup_nul() instead if the size is known exactly.
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 */
char *kstrndup(const char *s, size_t max, gfp_t gfp)
{
	size_t len;
	char *buf;

	if (!s)
		return NULL;

	len = strnlen(s, max);
	buf = kmalloc_track_caller(len+1, gfp);
	if (buf) {
		memcpy(buf, s, len);
		buf[len] = '\0';
	}
	return buf;
}
EXPORT_SYMBOL(kstrndup);

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/**
 * kmemdup - duplicate region of memory
 *
 * @src: memory region to duplicate
 * @len: memory region length
 * @gfp: GFP mask to use
 */
void *kmemdup(const void *src, size_t len, gfp_t gfp)
{
	void *p;

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	p = kmalloc_track_caller(len, gfp);
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	if (p)
		memcpy(p, src, len);
	return p;
}
EXPORT_SYMBOL(kmemdup);

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/**
 * kmemdup_nul - Create a NUL-terminated string from unterminated data
 * @s: The data to stringify
 * @len: The size of the data
 * @gfp: the GFP mask used in the kmalloc() call when allocating memory
 */
char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
{
	char *buf;

	if (!s)
		return NULL;

	buf = kmalloc_track_caller(len + 1, gfp);
	if (buf) {
		memcpy(buf, s, len);
		buf[len] = '\0';
	}
	return buf;
}
EXPORT_SYMBOL(kmemdup_nul);

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/**
 * memdup_user - duplicate memory region from user space
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
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 * Returns an ERR_PTR() on failure.  Result is physically
 * contiguous, to be freed by kfree().
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 */
void *memdup_user(const void __user *src, size_t len)
{
	void *p;

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	p = kmalloc_track_caller(len, GFP_USER);
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	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kfree(p);
		return ERR_PTR(-EFAULT);
	}

	return p;
}
EXPORT_SYMBOL(memdup_user);

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/**
 * vmemdup_user - duplicate memory region from user space
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
 * Returns an ERR_PTR() on failure.  Result may be not
 * physically contiguous.  Use kvfree() to free.
 */
void *vmemdup_user(const void __user *src, size_t len)
{
	void *p;

	p = kvmalloc(len, GFP_USER);
	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kvfree(p);
		return ERR_PTR(-EFAULT);
	}

	return p;
}
EXPORT_SYMBOL(vmemdup_user);

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/**
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 * strndup_user - duplicate an existing string from user space
 * @s: The string to duplicate
 * @n: Maximum number of bytes to copy, including the trailing NUL.
 */
char *strndup_user(const char __user *s, long n)
{
	char *p;
	long length;

	length = strnlen_user(s, n);

	if (!length)
		return ERR_PTR(-EFAULT);

	if (length > n)
		return ERR_PTR(-EINVAL);

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	p = memdup_user(s, length);
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	if (IS_ERR(p))
		return p;
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	p[length - 1] = '\0';

	return p;
}
EXPORT_SYMBOL(strndup_user);
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/**
 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
 * Returns an ERR_PTR() on failure.
 */
void *memdup_user_nul(const void __user *src, size_t len)
{
	char *p;

	/*
	 * Always use GFP_KERNEL, since copy_from_user() can sleep and
	 * cause pagefault, which makes it pointless to use GFP_NOFS
	 * or GFP_ATOMIC.
	 */
	p = kmalloc_track_caller(len + 1, GFP_KERNEL);
	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kfree(p);
		return ERR_PTR(-EFAULT);
	}
	p[len] = '\0';

	return p;
}
EXPORT_SYMBOL(memdup_user_nul);

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void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
		struct vm_area_struct *prev, struct rb_node *rb_parent)
{
	struct vm_area_struct *next;

	vma->vm_prev = prev;
	if (prev) {
		next = prev->vm_next;
		prev->vm_next = vma;
	} else {
		mm->mmap = vma;
		if (rb_parent)
			next = rb_entry(rb_parent,
					struct vm_area_struct, vm_rb);
		else
			next = NULL;
	}
	vma->vm_next = next;
	if (next)
		next->vm_prev = vma;
}

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/* Check if the vma is being used as a stack by this task */
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int vma_is_stack_for_current(struct vm_area_struct *vma)
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{
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	struct task_struct * __maybe_unused t = current;

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	return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
}

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#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
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void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
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{
	mm->mmap_base = TASK_UNMAPPED_BASE;
	mm->get_unmapped_area = arch_get_unmapped_area;
}
#endif
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/*
 * Like get_user_pages_fast() except its IRQ-safe in that it won't fall
 * back to the regular GUP.
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 * Note a difference with get_user_pages_fast: this always returns the
 * number of pages pinned, 0 if no pages were pinned.
 * If the architecture does not support this function, simply return with no
 * pages pinned.
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 */
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int __weak __get_user_pages_fast(unsigned long start,
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				 int nr_pages, int write, struct page **pages)
{
	return 0;
}
EXPORT_SYMBOL_GPL(__get_user_pages_fast);

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/**
 * get_user_pages_fast() - pin user pages in memory
 * @start:	starting user address
 * @nr_pages:	number of pages from start to pin
 * @write:	whether pages will be written to
 * @pages:	array that receives pointers to the pages pinned.
 *		Should be at least nr_pages long.
 *
 * Returns number of pages pinned. This may be fewer than the number
 * requested. If nr_pages is 0 or negative, returns 0. If no pages
 * were pinned, returns -errno.
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 *
 * get_user_pages_fast provides equivalent functionality to get_user_pages,
 * operating on current and current->mm, with force=0 and vma=NULL. However
 * unlike get_user_pages, it must be called without mmap_sem held.
 *
 * get_user_pages_fast may take mmap_sem and page table locks, so no
 * assumptions can be made about lack of locking. get_user_pages_fast is to be
 * implemented in a way that is advantageous (vs get_user_pages()) when the
 * user memory area is already faulted in and present in ptes. However if the
 * pages have to be faulted in, it may turn out to be slightly slower so
 * callers need to carefully consider what to use. On many architectures,
 * get_user_pages_fast simply falls back to get_user_pages.
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 */
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int __weak get_user_pages_fast(unsigned long start,
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				int nr_pages, int write, struct page **pages)
{
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	return get_user_pages_unlocked(start, nr_pages, pages,
				       write ? FOLL_WRITE : 0);
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}
EXPORT_SYMBOL_GPL(get_user_pages_fast);
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unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
	unsigned long len, unsigned long prot,
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	unsigned long flag, unsigned long pgoff)
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{
	unsigned long ret;
	struct mm_struct *mm = current->mm;
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	unsigned long populate;
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	LIST_HEAD(uf);
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	ret = security_mmap_file(file, prot, flag);
	if (!ret) {
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		if (down_write_killable(&mm->mmap_sem))
			return -EINTR;
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		ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff,
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				    &populate, &uf);
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		up_write(&mm->mmap_sem);
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		userfaultfd_unmap_complete(mm, &uf);
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		if (populate)
			mm_populate(ret, populate);
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	}
	return ret;
}

unsigned long vm_mmap(struct file *file, unsigned long addr,
	unsigned long len, unsigned long prot,
	unsigned long flag, unsigned long offset)
{
	if (unlikely(offset + PAGE_ALIGN(len) < offset))
		return -EINVAL;
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	if (unlikely(offset_in_page(offset)))
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		return -EINVAL;

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	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
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}
EXPORT_SYMBOL(vm_mmap);

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/**
 * kvmalloc_node - attempt to allocate physically contiguous memory, but upon
 * failure, fall back to non-contiguous (vmalloc) allocation.
 * @size: size of the request.
 * @flags: gfp mask for the allocation - must be compatible (superset) with GFP_KERNEL.
 * @node: numa node to allocate from
 *
 * Uses kmalloc to get the memory but if the allocation fails then falls back
 * to the vmalloc allocator. Use kvfree for freeing the memory.
 *
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 * Reclaim modifiers - __GFP_NORETRY and __GFP_NOFAIL are not supported.
 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
 * preferable to the vmalloc fallback, due to visible performance drawbacks.
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 *
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 * Please note that any use of gfp flags outside of GFP_KERNEL is careful to not
 * fall back to vmalloc.
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 */
void *kvmalloc_node(size_t size, gfp_t flags, int node)
{
	gfp_t kmalloc_flags = flags;
	void *ret;

	/*
	 * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
	 * so the given set of flags has to be compatible.
	 */
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	if ((flags & GFP_KERNEL) != GFP_KERNEL)
		return kmalloc_node(size, flags, node);
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	/*
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	 * We want to attempt a large physically contiguous block first because
	 * it is less likely to fragment multiple larger blocks and therefore
	 * contribute to a long term fragmentation less than vmalloc fallback.
	 * However make sure that larger requests are not too disruptive - no
	 * OOM killer and no allocation failure warnings as we have a fallback.
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	 */
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	if (size > PAGE_SIZE) {
		kmalloc_flags |= __GFP_NOWARN;

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		if (!(kmalloc_flags & __GFP_RETRY_MAYFAIL))
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			kmalloc_flags |= __GFP_NORETRY;
	}
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	ret = kmalloc_node(size, kmalloc_flags, node);

	/*
	 * It doesn't really make sense to fallback to vmalloc for sub page
	 * requests
	 */
	if (ret || size <= PAGE_SIZE)
		return ret;

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	return __vmalloc_node_flags_caller(size, node, flags,
			__builtin_return_address(0));
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}
EXPORT_SYMBOL(kvmalloc_node);

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/**
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 * kvfree() - Free memory.
 * @addr: Pointer to allocated memory.
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 *
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 * kvfree frees memory allocated by any of vmalloc(), kmalloc() or kvmalloc().
 * It is slightly more efficient to use kfree() or vfree() if you are certain
 * that you know which one to use.
 *
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 * Context: Either preemptible task context or not-NMI interrupt.
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 */
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void kvfree(const void *addr)
{
	if (is_vmalloc_addr(addr))
		vfree(addr);
	else
		kfree(addr);
}
EXPORT_SYMBOL(kvfree);

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static inline void *__page_rmapping(struct page *page)
{
	unsigned long mapping;

	mapping = (unsigned long)page->mapping;
	mapping &= ~PAGE_MAPPING_FLAGS;

	return (void *)mapping;
}

/* Neutral page->mapping pointer to address_space or anon_vma or other */
void *page_rmapping(struct page *page)
{
	page = compound_head(page);
	return __page_rmapping(page);
}

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/*
 * Return true if this page is mapped into pagetables.
 * For compound page it returns true if any subpage of compound page is mapped.
 */
bool page_mapped(struct page *page)
{
	int i;

	if (likely(!PageCompound(page)))
		return atomic_read(&page->_mapcount) >= 0;
	page = compound_head(page);
	if (atomic_read(compound_mapcount_ptr(page)) >= 0)
		return true;
	if (PageHuge(page))
		return false;
	for (i = 0; i < hpage_nr_pages(page); i++) {
		if (atomic_read(&page[i]._mapcount) >= 0)
			return true;
	}
	return false;
}
EXPORT_SYMBOL(page_mapped);

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struct anon_vma *page_anon_vma(struct page *page)
{
	unsigned long mapping;

	page = compound_head(page);
	mapping = (unsigned long)page->mapping;
	if ((mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
		return NULL;
	return __page_rmapping(page);
}

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struct address_space *page_mapping(struct page *page)
{
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	struct address_space *mapping;

	page = compound_head(page);
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	/* This happens if someone calls flush_dcache_page on slab page */
	if (unlikely(PageSlab(page)))
		return NULL;

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	if (unlikely(PageSwapCache(page))) {
		swp_entry_t entry;

		entry.val = page_private(page);
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		return swap_address_space(entry);
	}

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	mapping = page->mapping;
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	if ((unsigned long)mapping & PAGE_MAPPING_ANON)
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		return NULL;
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	return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS);
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}
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EXPORT_SYMBOL(page_mapping);
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/*
 * For file cache pages, return the address_space, otherwise return NULL
 */
struct address_space *page_mapping_file(struct page *page)
{
	if (unlikely(PageSwapCache(page)))
		return NULL;
	return page_mapping(page);
}

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/* Slow path of page_mapcount() for compound pages */
int __page_mapcount(struct page *page)
{
	int ret;

	ret = atomic_read(&page->_mapcount) + 1;
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	/*
	 * For file THP page->_mapcount contains total number of mapping
	 * of the page: no need to look into compound_mapcount.
	 */
	if (!PageAnon(page) && !PageHuge(page))
		return ret;
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	page = compound_head(page);
	ret += atomic_read(compound_mapcount_ptr(page)) + 1;
	if (PageDoubleMap(page))
		ret--;
	return ret;
}
EXPORT_SYMBOL_GPL(__page_mapcount);

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int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS;
int sysctl_overcommit_ratio __read_mostly = 50;
unsigned long sysctl_overcommit_kbytes __read_mostly;
int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */

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int overcommit_ratio_handler(struct ctl_table *table, int write,
			     void __user *buffer, size_t *lenp,
			     loff_t *ppos)
{
	int ret;

	ret = proc_dointvec(table, write, buffer, lenp, ppos);
	if (ret == 0 && write)
		sysctl_overcommit_kbytes = 0;
	return ret;
}

int overcommit_kbytes_handler(struct ctl_table *table, int write,
			     void __user *buffer, size_t *lenp,
			     loff_t *ppos)
{
	int ret;

	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
	if (ret == 0 && write)
		sysctl_overcommit_ratio = 0;
	return ret;
}

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/*
 * Committed memory limit enforced when OVERCOMMIT_NEVER policy is used
 */
unsigned long vm_commit_limit(void)
{
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	unsigned long allowed;

	if (sysctl_overcommit_kbytes)
		allowed = sysctl_overcommit_kbytes >> (PAGE_SHIFT - 10);
	else
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		allowed = ((totalram_pages() - hugetlb_total_pages())
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			   * sysctl_overcommit_ratio / 100);
	allowed += total_swap_pages;

	return allowed;
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}

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/*
 * Make sure vm_committed_as in one cacheline and not cacheline shared with
 * other variables. It can be updated by several CPUs frequently.
 */
struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;

/*
 * The global memory commitment made in the system can be a metric
 * that can be used to drive ballooning decisions when Linux is hosted
 * as a guest. On Hyper-V, the host implements a policy engine for dynamically
 * balancing memory across competing virtual machines that are hosted.
 * Several metrics drive this policy engine including the guest reported
 * memory commitment.
 */
unsigned long vm_memory_committed(void)
{
	return percpu_counter_read_positive(&vm_committed_as);
}
EXPORT_SYMBOL_GPL(vm_memory_committed);

/*
 * Check that a process has enough memory to allocate a new virtual
 * mapping. 0 means there is enough memory for the allocation to
 * succeed and -ENOMEM implies there is not.
 *
 * We currently support three overcommit policies, which are set via the
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 * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting.rst
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 *
 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 * Additional code 2002 Jul 20 by Robert Love.
 *
 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
 *
 * Note this is a helper function intended to be used by LSMs which
 * wish to use this logic.
 */
int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
{
	long free, allowed, reserve;

	VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) <
			-(s64)vm_committed_as_batch * num_online_cpus(),
			"memory commitment underflow");

	vm_acct_memory(pages);

	/*
	 * Sometimes we want to use more memory than we have
	 */
	if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
		return 0;

	if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
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		free = global_zone_page_state(NR_FREE_PAGES);
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		free += global_node_page_state(NR_FILE_PAGES);
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		/*
		 * shmem pages shouldn't be counted as free in this
		 * case, they can't be purged, only swapped out, and
		 * that won't affect the overall amount of available
		 * memory in the system.
		 */
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		free -= global_node_page_state(NR_SHMEM);
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		free += get_nr_swap_pages();

		/*
		 * Any slabs which are created with the
		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
		 * which are reclaimable, under pressure.  The dentry
		 * cache and most inode caches should fall into this
		 */
675
		free += global_node_page_state(NR_SLAB_RECLAIMABLE);
676

677 678 679 680
		/*
		 * Part of the kernel memory, which can be released
		 * under memory pressure.
		 */
681
		free += global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE);
682

683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725
		/*
		 * Leave reserved pages. The pages are not for anonymous pages.
		 */
		if (free <= totalreserve_pages)
			goto error;
		else
			free -= totalreserve_pages;

		/*
		 * Reserve some for root
		 */
		if (!cap_sys_admin)
			free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);

		if (free > pages)
			return 0;

		goto error;
	}

	allowed = vm_commit_limit();
	/*
	 * Reserve some for root
	 */
	if (!cap_sys_admin)
		allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);

	/*
	 * Don't let a single process grow so big a user can't recover
	 */
	if (mm) {
		reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
		allowed -= min_t(long, mm->total_vm / 32, reserve);
	}

	if (percpu_counter_read_positive(&vm_committed_as) < allowed)
		return 0;
error:
	vm_unacct_memory(pages);

	return -ENOMEM;
}

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/**
 * get_cmdline() - copy the cmdline value to a buffer.
 * @task:     the task whose cmdline value to copy.
 * @buffer:   the buffer to copy to.
 * @buflen:   the length of the buffer. Larger cmdline values are truncated
 *            to this length.
 * Returns the size of the cmdline field copied. Note that the copy does
 * not guarantee an ending NULL byte.
 */
int get_cmdline(struct task_struct *task, char *buffer, int buflen)
{
	int res = 0;
	unsigned int len;
	struct mm_struct *mm = get_task_mm(task);
740
	unsigned long arg_start, arg_end, env_start, env_end;
741 742 743 744 745
	if (!mm)
		goto out;
	if (!mm->arg_end)
		goto out_mm;	/* Shh! No looking before we're done */

746 747 748 749 750 751 752 753
	down_read(&mm->mmap_sem);
	arg_start = mm->arg_start;
	arg_end = mm->arg_end;
	env_start = mm->env_start;
	env_end = mm->env_end;
	up_read(&mm->mmap_sem);

	len = arg_end - arg_start;
754 755 756 757

	if (len > buflen)
		len = buflen;

758
	res = access_process_vm(task, arg_start, buffer, len, FOLL_FORCE);
759 760 761 762 763 764 765 766 767 768

	/*
	 * If the nul at the end of args has been overwritten, then
	 * assume application is using setproctitle(3).
	 */
	if (res > 0 && buffer[res-1] != '\0' && len < buflen) {
		len = strnlen(buffer, res);
		if (len < res) {
			res = len;
		} else {
769
			len = env_end - env_start;
770 771
			if (len > buflen - res)
				len = buflen - res;
772
			res += access_process_vm(task, env_start,
773 774
						 buffer+res, len,
						 FOLL_FORCE);
775 776 777 778 779 780 781 782
			res = strnlen(buffer, res);
		}
	}
out_mm:
	mmput(mm);
out:
	return res;
}