linux/mm/mremap.c
Vlastimil Babka d014cd7c1c mm, mremap: fix mremap() expanding for vma's with vm_ops->close()
Fabian has reported another regression in 6.1 due to ca3d76b0aa ("mm:
add merging after mremap resize").  The problem is that vma_merge() can
fail when vma has a vm_ops->close() method, causing is_mergeable_vma()
test to be negative.  This was happening for vma mapping a file from
fuse-overlayfs, which does have the method.  But when we are simply
expanding the vma, we never remove it due to the "merge" with the added
area, so the test should not prevent the expansion.

As a quick fix, check for such vmas and expand them using vma_adjust()
directly as was done before commit ca3d76b0aa.  For a more robust long
term solution we should try to limit the check for vma_ops->close only to
cases that actually result in vma removal, so that no merge would be
prevented unnecessarily.

[akpm@linux-foundation.org: fix indenting whitespace, reflow comment]
Link: https://lkml.kernel.org/r/20230117101939.9753-1-vbabka@suse.cz
Fixes: ca3d76b0aa ("mm: add merging after mremap resize")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Fabian Vogt <fvogt@suse.com>
  Link: https://bugzilla.suse.com/show_bug.cgi?id=1206359#c35
Tested-by: Fabian Vogt <fvogt@suse.com>
Cc: Jakub Matěna <matenajakub@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-01-31 16:44:08 -08:00

1106 lines
29 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* mm/mremap.c
*
* (C) Copyright 1996 Linus Torvalds
*
* Address space accounting code <alan@lxorguk.ukuu.org.uk>
* (C) Copyright 2002 Red Hat Inc, All Rights Reserved
*/
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/hugetlb.h>
#include <linux/shm.h>
#include <linux/ksm.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/capability.h>
#include <linux/fs.h>
#include <linux/swapops.h>
#include <linux/highmem.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/mmu_notifier.h>
#include <linux/uaccess.h>
#include <linux/userfaultfd_k.h>
#include <linux/mempolicy.h>
#include <asm/cacheflush.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.h"
static pud_t *get_old_pud(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pgd = pgd_offset(mm, addr);
if (pgd_none_or_clear_bad(pgd))
return NULL;
p4d = p4d_offset(pgd, addr);
if (p4d_none_or_clear_bad(p4d))
return NULL;
pud = pud_offset(p4d, addr);
if (pud_none_or_clear_bad(pud))
return NULL;
return pud;
}
static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
{
pud_t *pud;
pmd_t *pmd;
pud = get_old_pud(mm, addr);
if (!pud)
return NULL;
pmd = pmd_offset(pud, addr);
if (pmd_none(*pmd))
return NULL;
return pmd;
}
static pud_t *alloc_new_pud(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr)
{
pgd_t *pgd;
p4d_t *p4d;
pgd = pgd_offset(mm, addr);
p4d = p4d_alloc(mm, pgd, addr);
if (!p4d)
return NULL;
return pud_alloc(mm, p4d, addr);
}
static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr)
{
pud_t *pud;
pmd_t *pmd;
pud = alloc_new_pud(mm, vma, addr);
if (!pud)
return NULL;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
return NULL;
VM_BUG_ON(pmd_trans_huge(*pmd));
return pmd;
}
static void take_rmap_locks(struct vm_area_struct *vma)
{
if (vma->vm_file)
i_mmap_lock_write(vma->vm_file->f_mapping);
if (vma->anon_vma)
anon_vma_lock_write(vma->anon_vma);
}
static void drop_rmap_locks(struct vm_area_struct *vma)
{
if (vma->anon_vma)
anon_vma_unlock_write(vma->anon_vma);
if (vma->vm_file)
i_mmap_unlock_write(vma->vm_file->f_mapping);
}
static pte_t move_soft_dirty_pte(pte_t pte)
{
/*
* Set soft dirty bit so we can notice
* in userspace the ptes were moved.
*/
#ifdef CONFIG_MEM_SOFT_DIRTY
if (pte_present(pte))
pte = pte_mksoft_dirty(pte);
else if (is_swap_pte(pte))
pte = pte_swp_mksoft_dirty(pte);
#endif
return pte;
}
static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
unsigned long old_addr, unsigned long old_end,
struct vm_area_struct *new_vma, pmd_t *new_pmd,
unsigned long new_addr, bool need_rmap_locks)
{
struct mm_struct *mm = vma->vm_mm;
pte_t *old_pte, *new_pte, pte;
spinlock_t *old_ptl, *new_ptl;
bool force_flush = false;
unsigned long len = old_end - old_addr;
/*
* When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
* locks to ensure that rmap will always observe either the old or the
* new ptes. This is the easiest way to avoid races with
* truncate_pagecache(), page migration, etc...
*
* When need_rmap_locks is false, we use other ways to avoid
* such races:
*
* - During exec() shift_arg_pages(), we use a specially tagged vma
* which rmap call sites look for using vma_is_temporary_stack().
*
* - During mremap(), new_vma is often known to be placed after vma
* in rmap traversal order. This ensures rmap will always observe
* either the old pte, or the new pte, or both (the page table locks
* serialize access to individual ptes, but only rmap traversal
* order guarantees that we won't miss both the old and new ptes).
*/
if (need_rmap_locks)
take_rmap_locks(vma);
/*
* We don't have to worry about the ordering of src and dst
* pte locks because exclusive mmap_lock prevents deadlock.
*/
old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
new_pte = pte_offset_map(new_pmd, new_addr);
new_ptl = pte_lockptr(mm, new_pmd);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
flush_tlb_batched_pending(vma->vm_mm);
arch_enter_lazy_mmu_mode();
for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
new_pte++, new_addr += PAGE_SIZE) {
if (pte_none(*old_pte))
continue;
pte = ptep_get_and_clear(mm, old_addr, old_pte);
/*
* If we are remapping a valid PTE, make sure
* to flush TLB before we drop the PTL for the
* PTE.
*
* NOTE! Both old and new PTL matter: the old one
* for racing with page_mkclean(), the new one to
* make sure the physical page stays valid until
* the TLB entry for the old mapping has been
* flushed.
*/
if (pte_present(pte))
force_flush = true;
pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
pte = move_soft_dirty_pte(pte);
set_pte_at(mm, new_addr, new_pte, pte);
}
arch_leave_lazy_mmu_mode();
if (force_flush)
flush_tlb_range(vma, old_end - len, old_end);
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
pte_unmap(new_pte - 1);
pte_unmap_unlock(old_pte - 1, old_ptl);
if (need_rmap_locks)
drop_rmap_locks(vma);
}
#ifndef arch_supports_page_table_move
#define arch_supports_page_table_move arch_supports_page_table_move
static inline bool arch_supports_page_table_move(void)
{
return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) ||
IS_ENABLED(CONFIG_HAVE_MOVE_PUD);
}
#endif
#ifdef CONFIG_HAVE_MOVE_PMD
static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
{
spinlock_t *old_ptl, *new_ptl;
struct mm_struct *mm = vma->vm_mm;
pmd_t pmd;
if (!arch_supports_page_table_move())
return false;
/*
* The destination pmd shouldn't be established, free_pgtables()
* should have released it.
*
* However, there's a case during execve() where we use mremap
* to move the initial stack, and in that case the target area
* may overlap the source area (always moving down).
*
* If everything is PMD-aligned, that works fine, as moving
* each pmd down will clear the source pmd. But if we first
* have a few 4kB-only pages that get moved down, and then
* hit the "now the rest is PMD-aligned, let's do everything
* one pmd at a time", we will still have the old (now empty
* of any 4kB pages, but still there) PMD in the page table
* tree.
*
* Warn on it once - because we really should try to figure
* out how to do this better - but then say "I won't move
* this pmd".
*
* One alternative might be to just unmap the target pmd at
* this point, and verify that it really is empty. We'll see.
*/
if (WARN_ON_ONCE(!pmd_none(*new_pmd)))
return false;
/*
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_lock prevents deadlock.
*/
old_ptl = pmd_lock(vma->vm_mm, old_pmd);
new_ptl = pmd_lockptr(mm, new_pmd);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
/* Clear the pmd */
pmd = *old_pmd;
pmd_clear(old_pmd);
VM_BUG_ON(!pmd_none(*new_pmd));
pmd_populate(mm, new_pmd, pmd_pgtable(pmd));
flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
return true;
}
#else
static inline bool move_normal_pmd(struct vm_area_struct *vma,
unsigned long old_addr, unsigned long new_addr, pmd_t *old_pmd,
pmd_t *new_pmd)
{
return false;
}
#endif
#if CONFIG_PGTABLE_LEVELS > 2 && defined(CONFIG_HAVE_MOVE_PUD)
static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
{
spinlock_t *old_ptl, *new_ptl;
struct mm_struct *mm = vma->vm_mm;
pud_t pud;
if (!arch_supports_page_table_move())
return false;
/*
* The destination pud shouldn't be established, free_pgtables()
* should have released it.
*/
if (WARN_ON_ONCE(!pud_none(*new_pud)))
return false;
/*
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_lock prevents deadlock.
*/
old_ptl = pud_lock(vma->vm_mm, old_pud);
new_ptl = pud_lockptr(mm, new_pud);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
/* Clear the pud */
pud = *old_pud;
pud_clear(old_pud);
VM_BUG_ON(!pud_none(*new_pud));
pud_populate(mm, new_pud, pud_pgtable(pud));
flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
return true;
}
#else
static inline bool move_normal_pud(struct vm_area_struct *vma,
unsigned long old_addr, unsigned long new_addr, pud_t *old_pud,
pud_t *new_pud)
{
return false;
}
#endif
#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
{
spinlock_t *old_ptl, *new_ptl;
struct mm_struct *mm = vma->vm_mm;
pud_t pud;
/*
* The destination pud shouldn't be established, free_pgtables()
* should have released it.
*/
if (WARN_ON_ONCE(!pud_none(*new_pud)))
return false;
/*
* We don't have to worry about the ordering of src and dst
* ptlocks because exclusive mmap_lock prevents deadlock.
*/
old_ptl = pud_lock(vma->vm_mm, old_pud);
new_ptl = pud_lockptr(mm, new_pud);
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
/* Clear the pud */
pud = *old_pud;
pud_clear(old_pud);
VM_BUG_ON(!pud_none(*new_pud));
/* Set the new pud */
/* mark soft_ditry when we add pud level soft dirty support */
set_pud_at(mm, new_addr, new_pud, pud);
flush_pud_tlb_range(vma, old_addr, old_addr + HPAGE_PUD_SIZE);
if (new_ptl != old_ptl)
spin_unlock(new_ptl);
spin_unlock(old_ptl);
return true;
}
#else
static bool move_huge_pud(struct vm_area_struct *vma, unsigned long old_addr,
unsigned long new_addr, pud_t *old_pud, pud_t *new_pud)
{
WARN_ON_ONCE(1);
return false;
}
#endif
enum pgt_entry {
NORMAL_PMD,
HPAGE_PMD,
NORMAL_PUD,
HPAGE_PUD,
};
/*
* Returns an extent of the corresponding size for the pgt_entry specified if
* valid. Else returns a smaller extent bounded by the end of the source and
* destination pgt_entry.
*/
static __always_inline unsigned long get_extent(enum pgt_entry entry,
unsigned long old_addr, unsigned long old_end,
unsigned long new_addr)
{
unsigned long next, extent, mask, size;
switch (entry) {
case HPAGE_PMD:
case NORMAL_PMD:
mask = PMD_MASK;
size = PMD_SIZE;
break;
case HPAGE_PUD:
case NORMAL_PUD:
mask = PUD_MASK;
size = PUD_SIZE;
break;
default:
BUILD_BUG();
break;
}
next = (old_addr + size) & mask;
/* even if next overflowed, extent below will be ok */
extent = next - old_addr;
if (extent > old_end - old_addr)
extent = old_end - old_addr;
next = (new_addr + size) & mask;
if (extent > next - new_addr)
extent = next - new_addr;
return extent;
}
/*
* Attempts to speedup the move by moving entry at the level corresponding to
* pgt_entry. Returns true if the move was successful, else false.
*/
static bool move_pgt_entry(enum pgt_entry entry, struct vm_area_struct *vma,
unsigned long old_addr, unsigned long new_addr,
void *old_entry, void *new_entry, bool need_rmap_locks)
{
bool moved = false;
/* See comment in move_ptes() */
if (need_rmap_locks)
take_rmap_locks(vma);
switch (entry) {
case NORMAL_PMD:
moved = move_normal_pmd(vma, old_addr, new_addr, old_entry,
new_entry);
break;
case NORMAL_PUD:
moved = move_normal_pud(vma, old_addr, new_addr, old_entry,
new_entry);
break;
case HPAGE_PMD:
moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
move_huge_pmd(vma, old_addr, new_addr, old_entry,
new_entry);
break;
case HPAGE_PUD:
moved = IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
move_huge_pud(vma, old_addr, new_addr, old_entry,
new_entry);
break;
default:
WARN_ON_ONCE(1);
break;
}
if (need_rmap_locks)
drop_rmap_locks(vma);
return moved;
}
unsigned long move_page_tables(struct vm_area_struct *vma,
unsigned long old_addr, struct vm_area_struct *new_vma,
unsigned long new_addr, unsigned long len,
bool need_rmap_locks)
{
unsigned long extent, old_end;
struct mmu_notifier_range range;
pmd_t *old_pmd, *new_pmd;
pud_t *old_pud, *new_pud;
if (!len)
return 0;
old_end = old_addr + len;
if (is_vm_hugetlb_page(vma))
return move_hugetlb_page_tables(vma, new_vma, old_addr,
new_addr, len);
flush_cache_range(vma, old_addr, old_end);
mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm,
old_addr, old_end);
mmu_notifier_invalidate_range_start(&range);
for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
cond_resched();
/*
* If extent is PUD-sized try to speed up the move by moving at the
* PUD level if possible.
*/
extent = get_extent(NORMAL_PUD, old_addr, old_end, new_addr);
old_pud = get_old_pud(vma->vm_mm, old_addr);
if (!old_pud)
continue;
new_pud = alloc_new_pud(vma->vm_mm, vma, new_addr);
if (!new_pud)
break;
if (pud_trans_huge(*old_pud) || pud_devmap(*old_pud)) {
if (extent == HPAGE_PUD_SIZE) {
move_pgt_entry(HPAGE_PUD, vma, old_addr, new_addr,
old_pud, new_pud, need_rmap_locks);
/* We ignore and continue on error? */
continue;
}
} else if (IS_ENABLED(CONFIG_HAVE_MOVE_PUD) && extent == PUD_SIZE) {
if (move_pgt_entry(NORMAL_PUD, vma, old_addr, new_addr,
old_pud, new_pud, true))
continue;
}
extent = get_extent(NORMAL_PMD, old_addr, old_end, new_addr);
old_pmd = get_old_pmd(vma->vm_mm, old_addr);
if (!old_pmd)
continue;
new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
if (!new_pmd)
break;
if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) ||
pmd_devmap(*old_pmd)) {
if (extent == HPAGE_PMD_SIZE &&
move_pgt_entry(HPAGE_PMD, vma, old_addr, new_addr,
old_pmd, new_pmd, need_rmap_locks))
continue;
split_huge_pmd(vma, old_pmd, old_addr);
if (pmd_trans_unstable(old_pmd))
continue;
} else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) &&
extent == PMD_SIZE) {
/*
* If the extent is PMD-sized, try to speed the move by
* moving at the PMD level if possible.
*/
if (move_pgt_entry(NORMAL_PMD, vma, old_addr, new_addr,
old_pmd, new_pmd, true))
continue;
}
if (pte_alloc(new_vma->vm_mm, new_pmd))
break;
move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
new_pmd, new_addr, need_rmap_locks);
}
mmu_notifier_invalidate_range_end(&range);
return len + old_addr - old_end; /* how much done */
}
static unsigned long move_vma(struct vm_area_struct *vma,
unsigned long old_addr, unsigned long old_len,
unsigned long new_len, unsigned long new_addr,
bool *locked, unsigned long flags,
struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap)
{
long to_account = new_len - old_len;
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *new_vma;
unsigned long vm_flags = vma->vm_flags;
unsigned long new_pgoff;
unsigned long moved_len;
unsigned long excess = 0;
unsigned long hiwater_vm;
int split = 0;
int err = 0;
bool need_rmap_locks;
/*
* We'd prefer to avoid failure later on in do_munmap:
* which may split one vma into three before unmapping.
*/
if (mm->map_count >= sysctl_max_map_count - 3)
return -ENOMEM;
if (unlikely(flags & MREMAP_DONTUNMAP))
to_account = new_len;
if (vma->vm_ops && vma->vm_ops->may_split) {
if (vma->vm_start != old_addr)
err = vma->vm_ops->may_split(vma, old_addr);
if (!err && vma->vm_end != old_addr + old_len)
err = vma->vm_ops->may_split(vma, old_addr + old_len);
if (err)
return err;
}
/*
* Advise KSM to break any KSM pages in the area to be moved:
* it would be confusing if they were to turn up at the new
* location, where they happen to coincide with different KSM
* pages recently unmapped. But leave vma->vm_flags as it was,
* so KSM can come around to merge on vma and new_vma afterwards.
*/
err = ksm_madvise(vma, old_addr, old_addr + old_len,
MADV_UNMERGEABLE, &vm_flags);
if (err)
return err;
if (vm_flags & VM_ACCOUNT) {
if (security_vm_enough_memory_mm(mm, to_account >> PAGE_SHIFT))
return -ENOMEM;
}
new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
&need_rmap_locks);
if (!new_vma) {
if (vm_flags & VM_ACCOUNT)
vm_unacct_memory(to_account >> PAGE_SHIFT);
return -ENOMEM;
}
moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
need_rmap_locks);
if (moved_len < old_len) {
err = -ENOMEM;
} else if (vma->vm_ops && vma->vm_ops->mremap) {
err = vma->vm_ops->mremap(new_vma);
}
if (unlikely(err)) {
/*
* On error, move entries back from new area to old,
* which will succeed since page tables still there,
* and then proceed to unmap new area instead of old.
*/
move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
true);
vma = new_vma;
old_len = new_len;
old_addr = new_addr;
new_addr = err;
} else {
mremap_userfaultfd_prep(new_vma, uf);
}
if (is_vm_hugetlb_page(vma)) {
clear_vma_resv_huge_pages(vma);
}
/* Conceal VM_ACCOUNT so old reservation is not undone */
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) {
vma->vm_flags &= ~VM_ACCOUNT;
excess = vma->vm_end - vma->vm_start - old_len;
if (old_addr > vma->vm_start &&
old_addr + old_len < vma->vm_end)
split = 1;
}
/*
* If we failed to move page tables we still do total_vm increment
* since do_munmap() will decrement it by old_len == new_len.
*
* Since total_vm is about to be raised artificially high for a
* moment, we need to restore high watermark afterwards: if stats
* are taken meanwhile, total_vm and hiwater_vm appear too high.
* If this were a serious issue, we'd add a flag to do_munmap().
*/
hiwater_vm = mm->hiwater_vm;
vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT);
/* Tell pfnmap has moved from this vma */
if (unlikely(vma->vm_flags & VM_PFNMAP))
untrack_pfn_moved(vma);
if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) {
/* We always clear VM_LOCKED[ONFAULT] on the old vma */
vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
/*
* anon_vma links of the old vma is no longer needed after its page
* table has been moved.
*/
if (new_vma != vma && vma->vm_start == old_addr &&
vma->vm_end == (old_addr + old_len))
unlink_anon_vmas(vma);
/* Because we won't unmap we don't need to touch locked_vm */
return new_addr;
}
if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
/* OOM: unable to split vma, just get accounts right */
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
vm_acct_memory(old_len >> PAGE_SHIFT);
excess = 0;
}
if (vm_flags & VM_LOCKED) {
mm->locked_vm += new_len >> PAGE_SHIFT;
*locked = true;
}
mm->hiwater_vm = hiwater_vm;
/* Restore VM_ACCOUNT if one or two pieces of vma left */
if (excess) {
vma->vm_flags |= VM_ACCOUNT;
if (split)
find_vma(mm, vma->vm_end)->vm_flags |= VM_ACCOUNT;
}
return new_addr;
}
static struct vm_area_struct *vma_to_resize(unsigned long addr,
unsigned long old_len, unsigned long new_len, unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long pgoff;
vma = vma_lookup(mm, addr);
if (!vma)
return ERR_PTR(-EFAULT);
/*
* !old_len is a special case where an attempt is made to 'duplicate'
* a mapping. This makes no sense for private mappings as it will
* instead create a fresh/new mapping unrelated to the original. This
* is contrary to the basic idea of mremap which creates new mappings
* based on the original. There are no known use cases for this
* behavior. As a result, fail such attempts.
*/
if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n", current->comm, current->pid);
return ERR_PTR(-EINVAL);
}
if ((flags & MREMAP_DONTUNMAP) &&
(vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
return ERR_PTR(-EINVAL);
/* We can't remap across vm area boundaries */
if (old_len > vma->vm_end - addr)
return ERR_PTR(-EFAULT);
if (new_len == old_len)
return vma;
/* Need to be careful about a growing mapping */
pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
pgoff += vma->vm_pgoff;
if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
return ERR_PTR(-EINVAL);
if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
return ERR_PTR(-EFAULT);
if (mlock_future_check(mm, vma->vm_flags, new_len - old_len))
return ERR_PTR(-EAGAIN);
if (!may_expand_vm(mm, vma->vm_flags,
(new_len - old_len) >> PAGE_SHIFT))
return ERR_PTR(-ENOMEM);
return vma;
}
static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
unsigned long new_addr, unsigned long new_len, bool *locked,
unsigned long flags, struct vm_userfaultfd_ctx *uf,
struct list_head *uf_unmap_early,
struct list_head *uf_unmap)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long ret = -EINVAL;
unsigned long map_flags = 0;
if (offset_in_page(new_addr))
goto out;
if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
goto out;
/* Ensure the old/new locations do not overlap */
if (addr + old_len > new_addr && new_addr + new_len > addr)
goto out;
/*
* move_vma() need us to stay 4 maps below the threshold, otherwise
* it will bail out at the very beginning.
* That is a problem if we have already unmaped the regions here
* (new_addr, and old_addr), because userspace will not know the
* state of the vma's after it gets -ENOMEM.
* So, to avoid such scenario we can pre-compute if the whole
* operation has high chances to success map-wise.
* Worst-scenario case is when both vma's (new_addr and old_addr) get
* split in 3 before unmapping it.
* That means 2 more maps (1 for each) to the ones we already hold.
* Check whether current map count plus 2 still leads us to 4 maps below
* the threshold, otherwise return -ENOMEM here to be more safe.
*/
if ((mm->map_count + 2) >= sysctl_max_map_count - 3)
return -ENOMEM;
if (flags & MREMAP_FIXED) {
ret = do_munmap(mm, new_addr, new_len, uf_unmap_early);
if (ret)
goto out;
}
if (old_len > new_len) {
ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
if (ret)
goto out;
old_len = new_len;
}
vma = vma_to_resize(addr, old_len, new_len, flags);
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto out;
}
/* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */
if (flags & MREMAP_DONTUNMAP &&
!may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) {
ret = -ENOMEM;
goto out;
}
if (flags & MREMAP_FIXED)
map_flags |= MAP_FIXED;
if (vma->vm_flags & VM_MAYSHARE)
map_flags |= MAP_SHARED;
ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
((addr - vma->vm_start) >> PAGE_SHIFT),
map_flags);
if (IS_ERR_VALUE(ret))
goto out;
/* We got a new mapping */
if (!(flags & MREMAP_FIXED))
new_addr = ret;
ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf,
uf_unmap);
out:
return ret;
}
static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
{
unsigned long end = vma->vm_end + delta;
if (end < vma->vm_end) /* overflow */
return 0;
if (find_vma_intersection(vma->vm_mm, vma->vm_end, end))
return 0;
if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
0, MAP_FIXED) & ~PAGE_MASK)
return 0;
return 1;
}
/*
* Expand (or shrink) an existing mapping, potentially moving it at the
* same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
*
* MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
* This option implies MREMAP_MAYMOVE.
*/
SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
unsigned long, new_len, unsigned long, flags,
unsigned long, new_addr)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long ret = -EINVAL;
bool locked = false;
bool downgraded = false;
struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX;
LIST_HEAD(uf_unmap_early);
LIST_HEAD(uf_unmap);
/*
* There is a deliberate asymmetry here: we strip the pointer tag
* from the old address but leave the new address alone. This is
* for consistency with mmap(), where we prevent the creation of
* aliasing mappings in userspace by leaving the tag bits of the
* mapping address intact. A non-zero tag will cause the subsequent
* range checks to reject the address as invalid.
*
* See Documentation/arm64/tagged-address-abi.rst for more information.
*/
addr = untagged_addr(addr);
if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
return ret;
if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
return ret;
/*
* MREMAP_DONTUNMAP is always a move and it does not allow resizing
* in the process.
*/
if (flags & MREMAP_DONTUNMAP &&
(!(flags & MREMAP_MAYMOVE) || old_len != new_len))
return ret;
if (offset_in_page(addr))
return ret;
old_len = PAGE_ALIGN(old_len);
new_len = PAGE_ALIGN(new_len);
/*
* We allow a zero old-len as a special case
* for DOS-emu "duplicate shm area" thing. But
* a zero new-len is nonsensical.
*/
if (!new_len)
return ret;
if (mmap_write_lock_killable(current->mm))
return -EINTR;
vma = vma_lookup(mm, addr);
if (!vma) {
ret = -EFAULT;
goto out;
}
if (is_vm_hugetlb_page(vma)) {
struct hstate *h __maybe_unused = hstate_vma(vma);
old_len = ALIGN(old_len, huge_page_size(h));
new_len = ALIGN(new_len, huge_page_size(h));
/* addrs must be huge page aligned */
if (addr & ~huge_page_mask(h))
goto out;
if (new_addr & ~huge_page_mask(h))
goto out;
/*
* Don't allow remap expansion, because the underlying hugetlb
* reservation is not yet capable to handle split reservation.
*/
if (new_len > old_len)
goto out;
}
if (flags & (MREMAP_FIXED | MREMAP_DONTUNMAP)) {
ret = mremap_to(addr, old_len, new_addr, new_len,
&locked, flags, &uf, &uf_unmap_early,
&uf_unmap);
goto out;
}
/*
* Always allow a shrinking remap: that just unmaps
* the unnecessary pages..
* do_mas_munmap does all the needed commit accounting, and
* downgrades mmap_lock to read if so directed.
*/
if (old_len >= new_len) {
int retval;
MA_STATE(mas, &mm->mm_mt, addr + new_len, addr + new_len);
retval = do_mas_munmap(&mas, mm, addr + new_len,
old_len - new_len, &uf_unmap, true);
/* Returning 1 indicates mmap_lock is downgraded to read. */
if (retval == 1) {
downgraded = true;
} else if (retval < 0 && old_len != new_len) {
ret = retval;
goto out;
}
ret = addr;
goto out;
}
/*
* Ok, we need to grow..
*/
vma = vma_to_resize(addr, old_len, new_len, flags);
if (IS_ERR(vma)) {
ret = PTR_ERR(vma);
goto out;
}
/* old_len exactly to the end of the area..
*/
if (old_len == vma->vm_end - addr) {
/* can we just expand the current mapping? */
if (vma_expandable(vma, new_len - old_len)) {
long pages = (new_len - old_len) >> PAGE_SHIFT;
unsigned long extension_start = addr + old_len;
unsigned long extension_end = addr + new_len;
pgoff_t extension_pgoff = vma->vm_pgoff +
((extension_start - vma->vm_start) >> PAGE_SHIFT);
if (vma->vm_flags & VM_ACCOUNT) {
if (security_vm_enough_memory_mm(mm, pages)) {
ret = -ENOMEM;
goto out;
}
}
/*
* Function vma_merge() is called on the extension we
* are adding to the already existing vma, vma_merge()
* will merge this extension with the already existing
* vma (expand operation itself) and possibly also with
* the next vma if it becomes adjacent to the expanded
* vma and otherwise compatible.
*
* However, vma_merge() can currently fail due to
* is_mergeable_vma() check for vm_ops->close (see the
* comment there). Yet this should not prevent vma
* expanding, so perform a simple expand for such vma.
* Ideally the check for close op should be only done
* when a vma would be actually removed due to a merge.
*/
if (!vma->vm_ops || !vma->vm_ops->close) {
vma = vma_merge(mm, vma, extension_start, extension_end,
vma->vm_flags, vma->anon_vma, vma->vm_file,
extension_pgoff, vma_policy(vma),
vma->vm_userfaultfd_ctx, anon_vma_name(vma));
} else if (vma_adjust(vma, vma->vm_start, addr + new_len,
vma->vm_pgoff, NULL)) {
vma = NULL;
}
if (!vma) {
vm_unacct_memory(pages);
ret = -ENOMEM;
goto out;
}
vm_stat_account(mm, vma->vm_flags, pages);
if (vma->vm_flags & VM_LOCKED) {
mm->locked_vm += pages;
locked = true;
new_addr = addr;
}
ret = addr;
goto out;
}
}
/*
* We weren't able to just expand or shrink the area,
* we need to create a new one and move it..
*/
ret = -ENOMEM;
if (flags & MREMAP_MAYMOVE) {
unsigned long map_flags = 0;
if (vma->vm_flags & VM_MAYSHARE)
map_flags |= MAP_SHARED;
new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
vma->vm_pgoff +
((addr - vma->vm_start) >> PAGE_SHIFT),
map_flags);
if (IS_ERR_VALUE(new_addr)) {
ret = new_addr;
goto out;
}
ret = move_vma(vma, addr, old_len, new_len, new_addr,
&locked, flags, &uf, &uf_unmap);
}
out:
if (offset_in_page(ret))
locked = false;
if (downgraded)
mmap_read_unlock(current->mm);
else
mmap_write_unlock(current->mm);
if (locked && new_len > old_len)
mm_populate(new_addr + old_len, new_len - old_len);
userfaultfd_unmap_complete(mm, &uf_unmap_early);
mremap_userfaultfd_complete(&uf, addr, ret, old_len);
userfaultfd_unmap_complete(mm, &uf_unmap);
return ret;
}