[PATCH 05/16] mm: Protect VMA modifications using VMA sequence count
From: Laurent Dufour
Date: Tue Aug 08 2017 - 10:39:33 EST
The VMA sequence count has been introduced to allow fast detection of
VMA modification when running a page fault handler without holding
the mmap_sem.
This patch provides protection agains the VMA modification done in :
- madvise()
- mremap()
- mpol_rebind_policy()
- vma_replace_policy()
- change_prot_numa()
- mlock(), munlock()
- mprotect()
- mmap_region()
- collapse_huge_page()
Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 2 ++
mm/khugepaged.c | 3 +++
mm/madvise.c | 4 ++++
mm/mempolicy.c | 10 +++++++++-
mm/mlock.c | 9 ++++++---
mm/mmap.c | 2 ++
mm/mprotect.c | 2 ++
mm/mremap.c | 7 +++++++
8 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index b836fd61ed87..5c0c3ab10f3c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1064,8 +1064,10 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
goto out_mm;
}
for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ write_seqcount_begin(&vma->vm_sequence);
vma->vm_flags &= ~VM_SOFTDIRTY;
vma_set_page_prot(vma);
+ write_seqcount_end(&vma->vm_sequence);
}
downgrade_write(&mm->mmap_sem);
break;
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index c01f177a1120..56dd994c05d0 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1005,6 +1005,7 @@ static void collapse_huge_page(struct mm_struct *mm,
if (mm_find_pmd(mm, address) != pmd)
goto out;
+ write_seqcount_begin(&vma->vm_sequence);
anon_vma_lock_write(vma->anon_vma);
pte = pte_offset_map(pmd, address);
@@ -1040,6 +1041,7 @@ static void collapse_huge_page(struct mm_struct *mm,
pmd_populate(mm, pmd, pmd_pgtable(_pmd));
spin_unlock(pmd_ptl);
anon_vma_unlock_write(vma->anon_vma);
+ write_seqcount_end(&vma->vm_sequence);
result = SCAN_FAIL;
goto out;
}
@@ -1074,6 +1076,7 @@ static void collapse_huge_page(struct mm_struct *mm,
set_pmd_at(mm, address, pmd, _pmd);
update_mmu_cache_pmd(vma, address, pmd);
spin_unlock(pmd_ptl);
+ write_seqcount_end(&vma->vm_sequence);
*hpage = NULL;
diff --git a/mm/madvise.c b/mm/madvise.c
index 47d8d8a25eae..4f73ecaa0961 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -172,7 +172,9 @@ static long madvise_behavior(struct vm_area_struct *vma,
/*
* vm_flags is protected by the mmap_sem held in write mode.
*/
+ write_seqcount_begin(&vma->vm_sequence);
vma->vm_flags = new_flags;
+ write_seqcount_end(&vma->vm_sequence);
out:
return error;
}
@@ -440,9 +442,11 @@ static void madvise_free_page_range(struct mmu_gather *tlb,
.private = tlb,
};
+ write_seqcount_begin(&vma->vm_sequence);
tlb_start_vma(tlb, vma);
walk_page_range(addr, end, &free_walk);
tlb_end_vma(tlb, vma);
+ write_seqcount_end(&vma->vm_sequence);
}
static int madvise_free_single_vma(struct vm_area_struct *vma,
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d911fa5cb2a7..32ed50c0d4b2 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -378,8 +378,11 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
struct vm_area_struct *vma;
down_write(&mm->mmap_sem);
- for (vma = mm->mmap; vma; vma = vma->vm_next)
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ write_seqcount_begin(&vma->vm_sequence);
mpol_rebind_policy(vma->vm_policy, new);
+ write_seqcount_end(&vma->vm_sequence);
+ }
up_write(&mm->mmap_sem);
}
@@ -537,9 +540,11 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
{
int nr_updated;
+ write_seqcount_begin(&vma->vm_sequence);
nr_updated = change_protection(vma, addr, end, PAGE_NONE, 0, 1);
if (nr_updated)
count_vm_numa_events(NUMA_PTE_UPDATES, nr_updated);
+ write_seqcount_end(&vma->vm_sequence);
return nr_updated;
}
@@ -640,6 +645,7 @@ static int vma_replace_policy(struct vm_area_struct *vma,
if (IS_ERR(new))
return PTR_ERR(new);
+ write_seqcount_begin(&vma->vm_sequence);
if (vma->vm_ops && vma->vm_ops->set_policy) {
err = vma->vm_ops->set_policy(vma, new);
if (err)
@@ -648,10 +654,12 @@ static int vma_replace_policy(struct vm_area_struct *vma,
old = vma->vm_policy;
vma->vm_policy = new; /* protected by mmap_sem */
+ write_seqcount_end(&vma->vm_sequence);
mpol_put(old);
return 0;
err_out:
+ write_seqcount_end(&vma->vm_sequence);
mpol_put(new);
return err;
}
diff --git a/mm/mlock.c b/mm/mlock.c
index b562b5523a65..30d9bfc61929 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -438,7 +438,9 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
void munlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
+ write_seqcount_begin(&vma->vm_sequence);
vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
+ write_seqcount_end(&vma->vm_sequence);
while (start < end) {
struct page *page;
@@ -563,10 +565,11 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
* It's okay if try_to_unmap_one unmaps a page just after we
* set VM_LOCKED, populate_vma_page_range will bring it back.
*/
-
- if (lock)
+ if (lock) {
+ write_seqcount_begin(&vma->vm_sequence);
vma->vm_flags = newflags;
- else
+ write_seqcount_end(&vma->vm_sequence);
+ } else
munlock_vma_pages_range(vma, start, end);
out:
diff --git a/mm/mmap.c b/mm/mmap.c
index 140b22136cb7..221b1f3e966a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1734,6 +1734,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
out:
perf_event_mmap(vma);
+ write_seqcount_begin(&vma->vm_sequence);
vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
if (vm_flags & VM_LOCKED) {
if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
@@ -1756,6 +1757,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
vma->vm_flags |= VM_SOFTDIRTY;
vma_set_page_prot(vma);
+ write_seqcount_end(&vma->vm_sequence);
return addr;
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 4180ad8cc9c5..297f0f1e7560 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -344,6 +344,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
* vm_flags and vm_page_prot are protected by the mmap_sem
* held in write mode.
*/
+ write_seqcount_begin(&vma->vm_sequence);
vma->vm_flags = newflags;
dirty_accountable = vma_wants_writenotify(vma, vma->vm_page_prot);
vma_set_page_prot(vma);
@@ -359,6 +360,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
(newflags & VM_WRITE)) {
populate_vma_page_range(vma, start, end, NULL);
}
+ write_seqcount_end(&vma->vm_sequence);
vm_stat_account(mm, oldflags, -nrpages);
vm_stat_account(mm, newflags, nrpages);
diff --git a/mm/mremap.c b/mm/mremap.c
index 3f23715d3c69..1abadea8ab84 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -301,6 +301,10 @@ static unsigned long move_vma(struct vm_area_struct *vma,
if (!new_vma)
return -ENOMEM;
+ write_seqcount_begin(&vma->vm_sequence);
+ write_seqcount_begin_nested(&new_vma->vm_sequence,
+ SINGLE_DEPTH_NESTING);
+
moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
need_rmap_locks);
if (moved_len < old_len) {
@@ -317,6 +321,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
*/
move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
true);
+ write_seqcount_end(&vma->vm_sequence);
vma = new_vma;
old_len = new_len;
old_addr = new_addr;
@@ -325,7 +330,9 @@ static unsigned long move_vma(struct vm_area_struct *vma,
mremap_userfaultfd_prep(new_vma, uf);
arch_remap(mm, old_addr, old_addr + old_len,
new_addr, new_addr + new_len);
+ write_seqcount_end(&vma->vm_sequence);
}
+ write_seqcount_end(&new_vma->vm_sequence);
/* Conceal VM_ACCOUNT so old reservation is not undone */
if (vm_flags & VM_ACCOUNT) {
--
2.7.4