[linux-2.6-block.git] / mm / mprotect.c

/*
 *  mm/mprotect.c
 *
 *  (C) Copyright 1994 Linus Torvalds
 *  (C) Copyright 2002 Christoph Hellwig
 *
 *  Address space accounting code	<alan@lxorguk.ukuu.org.uk>
 *  (C) Copyright 2002 Red Hat Inc, All Rights Reserved
 */

#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/shm.h>
#include <linux/mman.h>
#include <linux/fs.h>
#include <linux/highmem.h>
#include <linux/security.h>
#include <linux/mempolicy.h>
#include <linux/personality.h>
#include <linux/syscalls.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/mmu_notifier.h>
#include <linux/migrate.h>
#include <linux/perf_event.h>
#include <linux/ksm.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

#ifndef pgprot_modify
static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
{
	return newprot;
}
#endif

static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
		unsigned long addr, unsigned long end, pgprot_t newprot,
		int dirty_accountable, int prot_numa)
{
	struct mm_struct *mm = vma->vm_mm;
	pte_t *pte, oldpte;
	spinlock_t *ptl;
	unsigned long pages = 0;

	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
	arch_enter_lazy_mmu_mode();
	do {
		oldpte = *pte;
		if (pte_present(oldpte)) {
			pte_t ptent;
			bool updated = false;

			if (!prot_numa) {
				ptent = ptep_modify_prot_start(mm, addr, pte);
				if (pte_numa(ptent))
					ptent = pte_mknonnuma(ptent);
				ptent = pte_modify(ptent, newprot);
				/*
				 * Avoid taking write faults for pages we
				 * know to be dirty.
				 */
				if (dirty_accountable && pte_dirty(ptent))
					ptent = pte_mkwrite(ptent);
				ptep_modify_prot_commit(mm, addr, pte, ptent);
				updated = true;
			} else {
				struct page *page;

				page = vm_normal_page(vma, addr, oldpte);
				if (page && !PageKsm(page)) {
					if (!pte_numa(oldpte)) {
						ptep_set_numa(mm, addr, pte);
						updated = true;
					}
				}
			}
			if (updated)
				pages++;
		} else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
			swp_entry_t entry = pte_to_swp_entry(oldpte);

			if (is_write_migration_entry(entry)) {
				pte_t newpte;
				/*
				 * A protection check is difficult so
				 * just be safe and disable write
				 */
				make_migration_entry_read(&entry);
				newpte = swp_entry_to_pte(entry);
				if (pte_swp_soft_dirty(oldpte))
					newpte = pte_swp_mksoft_dirty(newpte);
				set_pte_at(mm, addr, pte, newpte);

				pages++;
			}
		}
	} while (pte++, addr += PAGE_SIZE, addr != end);
	arch_leave_lazy_mmu_mode();
	pte_unmap_unlock(pte - 1, ptl);

	return pages;
}

static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
		pud_t *pud, unsigned long addr, unsigned long end,
		pgprot_t newprot, int dirty_accountable, int prot_numa)
{
	pmd_t *pmd;
	unsigned long next;
	unsigned long pages = 0;
	unsigned long nr_huge_updates = 0;

	pmd = pmd_offset(pud, addr);
	do {
		unsigned long this_pages;

		next = pmd_addr_end(addr, end);
		if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd))
			continue;
		if (pmd_trans_huge(*pmd)) {
			if (next - addr != HPAGE_PMD_SIZE)
				split_huge_page_pmd(vma, addr, pmd);
			else {
				int nr_ptes = change_huge_pmd(vma, pmd, addr,
						newprot, prot_numa);

				if (nr_ptes) {
					if (nr_ptes == HPAGE_PMD_NR) {
						pages += HPAGE_PMD_NR;
						nr_huge_updates++;
					}
					continue;
				}
			}
			/* fall through, the trans huge pmd just split */
		}
		VM_BUG_ON(pmd_trans_huge(*pmd));
		this_pages = change_pte_range(vma, pmd, addr, next, newprot,
				 dirty_accountable, prot_numa);
		pages += this_pages;
	} while (pmd++, addr = next, addr != end);

	if (nr_huge_updates)
		count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
	return pages;
}

static inline unsigned long change_pud_range(struct vm_area_struct *vma,
		pgd_t *pgd, unsigned long addr, unsigned long end,
		pgprot_t newprot, int dirty_accountable, int prot_numa)
{
	pud_t *pud;
	unsigned long next;
	unsigned long pages = 0;

	pud = pud_offset(pgd, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_none_or_clear_bad(pud))
			continue;
		pages += change_pmd_range(vma, pud, addr, next, newprot,
				 dirty_accountable, prot_numa);
	} while (pud++, addr = next, addr != end);

	return pages;
}

static unsigned long change_protection_range(struct vm_area_struct *vma,
		unsigned long addr, unsigned long end, pgprot_t newprot,
		int dirty_accountable, int prot_numa)
{
	struct mm_struct *mm = vma->vm_mm;
	pgd_t *pgd;
	unsigned long next;
	unsigned long start = addr;
	unsigned long pages = 0;

	BUG_ON(addr >= end);
	pgd = pgd_offset(mm, addr);
	flush_cache_range(vma, addr, end);
	set_tlb_flush_pending(mm);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(pgd))
			continue;
		pages += change_pud_range(vma, pgd, addr, next, newprot,
				 dirty_accountable, prot_numa);
	} while (pgd++, addr = next, addr != end);

	/* Only flush the TLB if we actually modified any entries: */
	if (pages)
		flush_tlb_range(vma, start, end);
	clear_tlb_flush_pending(mm);

	return pages;
}

unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
		       unsigned long end, pgprot_t newprot,
		       int dirty_accountable, int prot_numa)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long pages;

	mmu_notifier_invalidate_range_start(mm, start, end);
	if (is_vm_hugetlb_page(vma))
		pages = hugetlb_change_protection(vma, start, end, newprot);
	else
		pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
	mmu_notifier_invalidate_range_end(mm, start, end);

	return pages;
}

int
mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
	unsigned long start, unsigned long end, unsigned long newflags)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long oldflags = vma->vm_flags;
	long nrpages = (end - start) >> PAGE_SHIFT;
	unsigned long charged = 0;
	pgoff_t pgoff;
	int error;
	int dirty_accountable = 0;

	if (newflags == oldflags) {
		*pprev = vma;
		return 0;
	}

	/*
	 * If we make a private mapping writable we increase our commit;
	 * but (without finer accounting) cannot reduce our commit if we
	 * make it unwritable again. hugetlb mapping were accounted for
	 * even if read-only so there is no need to account for them here
	 */
	if (newflags & VM_WRITE) {
		if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_HUGETLB|
						VM_SHARED|VM_NORESERVE))) {
			charged = nrpages;
			if (security_vm_enough_memory_mm(mm, charged))
				return -ENOMEM;
			newflags |= VM_ACCOUNT;
		}
	}

	/*
	 * First try to merge with previous and/or next vma.
	 */
	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
	*pprev = vma_merge(mm, *pprev, start, end, newflags,
			vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
	if (*pprev) {
		vma = *pprev;
		goto success;
	}

	*pprev = vma;

	if (start != vma->vm_start) {
		error = split_vma(mm, vma, start, 1);
		if (error)
			goto fail;
	}

	if (end != vma->vm_end) {
		error = split_vma(mm, vma, end, 0);
		if (error)
			goto fail;
	}

success:
	/*
	 * vm_flags and vm_page_prot are protected by the mmap_sem
	 * held in write mode.
	 */
	vma->vm_flags = newflags;
	vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
					  vm_get_page_prot(newflags));

	if (vma_wants_writenotify(vma)) {
		vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
		dirty_accountable = 1;
	}

	change_protection(vma, start, end, vma->vm_page_prot,
			  dirty_accountable, 0);

	vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
	vm_stat_account(mm, newflags, vma->vm_file, nrpages);
	perf_event_mmap(vma);
	return 0;

fail:
	vm_unacct_memory(charged);
	return error;
}

SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
		unsigned long, prot)
{
	unsigned long vm_flags, nstart, end, tmp, reqprot;
	struct vm_area_struct *vma, *prev;
	int error = -EINVAL;
	const int grows = prot & (PROT_GROWSDOWN|PROT_GROWSUP);
	prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
	if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
		return -EINVAL;

	if (start & ~PAGE_MASK)
		return -EINVAL;
	if (!len)
		return 0;
	len = PAGE_ALIGN(len);
	end = start + len;
	if (end <= start)
		return -ENOMEM;
	if (!arch_validate_prot(prot))
		return -EINVAL;

	reqprot = prot;
	/*
	 * Does the application expect PROT_READ to imply PROT_EXEC:
	 */
	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
		prot |= PROT_EXEC;

	vm_flags = calc_vm_prot_bits(prot);

	down_write(&current->mm->mmap_sem);

	vma = find_vma(current->mm, start);
	error = -ENOMEM;
	if (!vma)
		goto out;
	prev = vma->vm_prev;
	if (unlikely(grows & PROT_GROWSDOWN)) {
		if (vma->vm_start >= end)
			goto out;
		start = vma->vm_start;
		error = -EINVAL;
		if (!(vma->vm_flags & VM_GROWSDOWN))
			goto out;
	} else {
		if (vma->vm_start > start)
			goto out;
		if (unlikely(grows & PROT_GROWSUP)) {
			end = vma->vm_end;
			error = -EINVAL;
			if (!(vma->vm_flags & VM_GROWSUP))
				goto out;
		}
	}
	if (start > vma->vm_start)
		prev = vma;

	for (nstart = start ; ; ) {
		unsigned long newflags;

		/* Here we know that vma->vm_start <= nstart < vma->vm_end. */

		newflags = vm_flags;
		newflags |= (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));

		/* newflags >> 4 shift VM_MAY% in place of VM_% */
		if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
			error = -EACCES;
			goto out;
		}

		error = security_file_mprotect(vma, reqprot, prot);
		if (error)
			goto out;

		tmp = vma->vm_end;
		if (tmp > end)
			tmp = end;
		error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
		if (error)
			goto out;
		nstart = tmp;

		if (nstart < prev->vm_end)
			nstart = prev->vm_end;
		if (nstart >= end)
			goto out;

		vma = prev->vm_next;
		if (!vma || vma->vm_start != nstart) {
			error = -ENOMEM;
			goto out;
		}
	}
out:
	up_write(&current->mm->mmap_sem);
	return error;
}
Commit	Line	Data
	1	/*
	2	* mm/mprotect.c
	3	*
	4	* (C) Copyright 1994 Linus Torvalds
	5	* (C) Copyright 2002 Christoph Hellwig
	6	*
	7	* Address space accounting code <alan@lxorguk.ukuu.org.uk>
	8	* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
	9	*/
	10
	11	#include <linux/mm.h>
	12	#include <linux/hugetlb.h>
	13	#include <linux/shm.h>
	14	#include <linux/mman.h>
	15	#include <linux/fs.h>
	16	#include <linux/highmem.h>
	17	#include <linux/security.h>
	18	#include <linux/mempolicy.h>
	19	#include <linux/personality.h>
	20	#include <linux/syscalls.h>
	21	#include <linux/swap.h>
	22	#include <linux/swapops.h>
	23	#include <linux/mmu_notifier.h>
	24	#include <linux/migrate.h>
	25	#include <linux/perf_event.h>
	26	#include <linux/ksm.h>
	27	#include <asm/uaccess.h>
	28	#include <asm/pgtable.h>
	29	#include <asm/cacheflush.h>
	30	#include <asm/tlbflush.h>
	31
	32	#ifndef pgprot_modify
	33	static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
	34	{
	35	return newprot;
	36	}
	37	#endif
	38
	39	static unsigned long change_pte_range(struct vm_area_struct vma, pmd_t pmd,
	40	unsigned long addr, unsigned long end, pgprot_t newprot,
	41	int dirty_accountable, int prot_numa)
	42	{
	43	struct mm_struct *mm = vma->vm_mm;
	44	pte_t *pte, oldpte;
	45	spinlock_t *ptl;
	46	unsigned long pages = 0;
	47
	48	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
	49	arch_enter_lazy_mmu_mode();
	50	do {
	51	oldpte = *pte;
	52	if (pte_present(oldpte)) {
	53	pte_t ptent;
	54	bool updated = false;
	55
	56	if (!prot_numa) {
	57	ptent = ptep_modify_prot_start(mm, addr, pte);
	58	if (pte_numa(ptent))
	59	ptent = pte_mknonnuma(ptent);
	60	ptent = pte_modify(ptent, newprot);
	61	/*
	62	* Avoid taking write faults for pages we
	63	* know to be dirty.
	64	*/
	65	if (dirty_accountable && pte_dirty(ptent))
	66	ptent = pte_mkwrite(ptent);
	67	ptep_modify_prot_commit(mm, addr, pte, ptent);
	68	updated = true;
	69	} else {
	70	struct page *page;
	71
	72	page = vm_normal_page(vma, addr, oldpte);
	73	if (page && !PageKsm(page)) {
	74	if (!pte_numa(oldpte)) {
	75	ptep_set_numa(mm, addr, pte);
	76	updated = true;
	77	}
	78	}
	79	}
	80	if (updated)
	81	pages++;
	82	} else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
	83	swp_entry_t entry = pte_to_swp_entry(oldpte);
	84
	85	if (is_write_migration_entry(entry)) {
	86	pte_t newpte;
	87	/*
	88	* A protection check is difficult so
	89	* just be safe and disable write
	90	*/
	91	make_migration_entry_read(&entry);
	92	newpte = swp_entry_to_pte(entry);
	93	if (pte_swp_soft_dirty(oldpte))
	94	newpte = pte_swp_mksoft_dirty(newpte);
	95	set_pte_at(mm, addr, pte, newpte);
	96
	97	pages++;
	98	}
	99	}
	100	} while (pte++, addr += PAGE_SIZE, addr != end);
	101	arch_leave_lazy_mmu_mode();
	102	pte_unmap_unlock(pte - 1, ptl);
	103
	104	return pages;
	105	}
	106
	107	static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
	108	pud_t *pud, unsigned long addr, unsigned long end,
	109	pgprot_t newprot, int dirty_accountable, int prot_numa)
	110	{
	111	pmd_t *pmd;
	112	unsigned long next;
	113	unsigned long pages = 0;
	114	unsigned long nr_huge_updates = 0;
	115
	116	pmd = pmd_offset(pud, addr);
	117	do {
	118	unsigned long this_pages;
	119
	120	next = pmd_addr_end(addr, end);
	121	if (!pmd_trans_huge(*pmd) && pmd_none_or_clear_bad(pmd))
	122	continue;
	123	if (pmd_trans_huge(*pmd)) {
	124	if (next - addr != HPAGE_PMD_SIZE)
	125	split_huge_page_pmd(vma, addr, pmd);
	126	else {
	127	int nr_ptes = change_huge_pmd(vma, pmd, addr,
	128	newprot, prot_numa);
	129
	130	if (nr_ptes) {
	131	if (nr_ptes == HPAGE_PMD_NR) {
	132	pages += HPAGE_PMD_NR;
	133	nr_huge_updates++;
	134	}
	135	continue;
	136	}
	137	}
	138	/* fall through, the trans huge pmd just split */
	139	}
	140	VM_BUG_ON(pmd_trans_huge(*pmd));
	141	this_pages = change_pte_range(vma, pmd, addr, next, newprot,
	142	dirty_accountable, prot_numa);
	143	pages += this_pages;
	144	} while (pmd++, addr = next, addr != end);
	145
	146	if (nr_huge_updates)
	147	count_vm_numa_events(NUMA_HUGE_PTE_UPDATES, nr_huge_updates);
	148	return pages;
	149	}
	150
	151	static inline unsigned long change_pud_range(struct vm_area_struct *vma,
	152	pgd_t *pgd, unsigned long addr, unsigned long end,
	153	pgprot_t newprot, int dirty_accountable, int prot_numa)
	154	{
	155	pud_t *pud;
	156	unsigned long next;
	157	unsigned long pages = 0;
	158
	159	pud = pud_offset(pgd, addr);
	160	do {
	161	next = pud_addr_end(addr, end);
	162	if (pud_none_or_clear_bad(pud))
	163	continue;
	164	pages += change_pmd_range(vma, pud, addr, next, newprot,
	165	dirty_accountable, prot_numa);
	166	} while (pud++, addr = next, addr != end);
	167
	168	return pages;
	169	}
	170
	171	static unsigned long change_protection_range(struct vm_area_struct *vma,
	172	unsigned long addr, unsigned long end, pgprot_t newprot,
	173	int dirty_accountable, int prot_numa)
	174	{
	175	struct mm_struct *mm = vma->vm_mm;
	176	pgd_t *pgd;
	177	unsigned long next;
	178	unsigned long start = addr;
	179	unsigned long pages = 0;
	180
	181	BUG_ON(addr >= end);
	182	pgd = pgd_offset(mm, addr);
	183	flush_cache_range(vma, addr, end);
	184	set_tlb_flush_pending(mm);
	185	do {
	186	next = pgd_addr_end(addr, end);
	187	if (pgd_none_or_clear_bad(pgd))
	188	continue;
	189	pages += change_pud_range(vma, pgd, addr, next, newprot,
	190	dirty_accountable, prot_numa);
	191	} while (pgd++, addr = next, addr != end);
	192
	193	/* Only flush the TLB if we actually modified any entries: */
	194	if (pages)
	195	flush_tlb_range(vma, start, end);
	196	clear_tlb_flush_pending(mm);
	197
	198	return pages;
	199	}
	200
	201	unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
	202	unsigned long end, pgprot_t newprot,
	203	int dirty_accountable, int prot_numa)
	204	{
	205	struct mm_struct *mm = vma->vm_mm;
	206	unsigned long pages;
	207
	208	mmu_notifier_invalidate_range_start(mm, start, end);
	209	if (is_vm_hugetlb_page(vma))
	210	pages = hugetlb_change_protection(vma, start, end, newprot);
	211	else
	212	pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
	213	mmu_notifier_invalidate_range_end(mm, start, end);
	214
	215	return pages;
	216	}
	217
	218	int
	219	mprotect_fixup(struct vm_area_struct vma, struct vm_area_struct *pprev,
	220	unsigned long start, unsigned long end, unsigned long newflags)
	221	{
	222	struct mm_struct *mm = vma->vm_mm;
	223	unsigned long oldflags = vma->vm_flags;
	224	long nrpages = (end - start) >> PAGE_SHIFT;
	225	unsigned long charged = 0;
	226	pgoff_t pgoff;
	227	int error;
	228	int dirty_accountable = 0;
	229
	230	if (newflags == oldflags) {
	231	*pprev = vma;
	232	return 0;
	233	}
	234
	235	/*
	236	* If we make a private mapping writable we increase our commit;
	237	* but (without finer accounting) cannot reduce our commit if we
	238	* make it unwritable again. hugetlb mapping were accounted for
	239	* even if read-only so there is no need to account for them here
	240	*/
	241	if (newflags & VM_WRITE) {
	242	if (!(oldflags & (VM_ACCOUNT\|VM_WRITE\|VM_HUGETLB\|
	243	VM_SHARED\|VM_NORESERVE))) {
	244	charged = nrpages;
	245	if (security_vm_enough_memory_mm(mm, charged))
	246	return -ENOMEM;
	247	newflags \|= VM_ACCOUNT;
	248	}
	249	}
	250
	251	/*
	252	* First try to merge with previous and/or next vma.
	253	*/
	254	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
	255	pprev = vma_merge(mm, pprev, start, end, newflags,
	256	vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
	257	if (*pprev) {
	258	vma = *pprev;
	259	goto success;
	260	}
	261
	262	*pprev = vma;
	263
	264	if (start != vma->vm_start) {
	265	error = split_vma(mm, vma, start, 1);
	266	if (error)
	267	goto fail;
	268	}
	269
	270	if (end != vma->vm_end) {
	271	error = split_vma(mm, vma, end, 0);
	272	if (error)
	273	goto fail;
	274	}
	275
	276	success:
	277	/*
	278	* vm_flags and vm_page_prot are protected by the mmap_sem
	279	* held in write mode.
	280	*/
	281	vma->vm_flags = newflags;
	282	vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
	283	vm_get_page_prot(newflags));
	284
	285	if (vma_wants_writenotify(vma)) {
	286	vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
	287	dirty_accountable = 1;
	288	}
	289
	290	change_protection(vma, start, end, vma->vm_page_prot,
	291	dirty_accountable, 0);
	292
	293	vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
	294	vm_stat_account(mm, newflags, vma->vm_file, nrpages);
	295	perf_event_mmap(vma);
	296	return 0;
	297
	298	fail:
	299	vm_unacct_memory(charged);
	300	return error;
	301	}
	302
	303	SYSCALL_DEFINE3(mprotect, unsigned long, start, size_t, len,
	304	unsigned long, prot)
	305	{
	306	unsigned long vm_flags, nstart, end, tmp, reqprot;
	307	struct vm_area_struct vma, prev;
	308	int error = -EINVAL;
	309	const int grows = prot & (PROT_GROWSDOWN\|PROT_GROWSUP);
	310	prot &= ~(PROT_GROWSDOWN\|PROT_GROWSUP);
	311	if (grows == (PROT_GROWSDOWN\|PROT_GROWSUP)) /* can't be both */
	312	return -EINVAL;
	313
	314	if (start & ~PAGE_MASK)
	315	return -EINVAL;
	316	if (!len)
	317	return 0;
	318	len = PAGE_ALIGN(len);
	319	end = start + len;
	320	if (end <= start)
	321	return -ENOMEM;
	322	if (!arch_validate_prot(prot))
	323	return -EINVAL;
	324
	325	reqprot = prot;
	326	/*
	327	* Does the application expect PROT_READ to imply PROT_EXEC:
	328	*/
	329	if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
	330	prot \|= PROT_EXEC;
	331
	332	vm_flags = calc_vm_prot_bits(prot);
	333
	334	down_write(&current->mm->mmap_sem);
	335
	336	vma = find_vma(current->mm, start);
	337	error = -ENOMEM;
	338	if (!vma)
	339	goto out;
	340	prev = vma->vm_prev;
	341	if (unlikely(grows & PROT_GROWSDOWN)) {
	342	if (vma->vm_start >= end)
	343	goto out;
	344	start = vma->vm_start;
	345	error = -EINVAL;
	346	if (!(vma->vm_flags & VM_GROWSDOWN))
	347	goto out;
	348	} else {
	349	if (vma->vm_start > start)
	350	goto out;
	351	if (unlikely(grows & PROT_GROWSUP)) {
	352	end = vma->vm_end;
	353	error = -EINVAL;
	354	if (!(vma->vm_flags & VM_GROWSUP))
	355	goto out;
	356	}
	357	}
	358	if (start > vma->vm_start)
	359	prev = vma;
	360
	361	for (nstart = start ; ; ) {
	362	unsigned long newflags;
	363
	364	/* Here we know that vma->vm_start <= nstart < vma->vm_end. */
	365
	366	newflags = vm_flags;
	367	newflags \|= (vma->vm_flags & ~(VM_READ \| VM_WRITE \| VM_EXEC));
	368
	369	/* newflags >> 4 shift VM_MAY% in place of VM_% */
	370	if ((newflags & ~(newflags >> 4)) & (VM_READ \| VM_WRITE \| VM_EXEC)) {
	371	error = -EACCES;
	372	goto out;
	373	}
	374
	375	error = security_file_mprotect(vma, reqprot, prot);
	376	if (error)
	377	goto out;
	378
	379	tmp = vma->vm_end;
	380	if (tmp > end)
	381	tmp = end;
	382	error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
	383	if (error)
	384	goto out;
	385	nstart = tmp;
	386
	387	if (nstart < prev->vm_end)
	388	nstart = prev->vm_end;
	389	if (nstart >= end)
	390	goto out;
	391
	392	vma = prev->vm_next;
	393	if (!vma \|\| vma->vm_start != nstart) {
	394	error = -ENOMEM;
	395	goto out;
	396	}
	397	}
	398	out:
	399	up_write(&current->mm->mmap_sem);
	400	return error;
	401	}