[PATCH v2 6/7] mm: Introduce find_vma_filter_flags() helper

Kirill Tkhai
2019-05-20T14:00:34Z

This patch introduce a new helper, which returns
vma of enough length at given address, but only
if it does not contain passed flags.

v2: New

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
include/linux/mm.h | 3 +++
mm/mremap.c | 39 ++++++++++++++++++++++++++-------------
2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 54328d08dbdd..65ceb56acd44 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1515,6 +1515,9 @@ void unmap_mapping_pages(struct address_space *mapping,
pgoff_t start, pgoff_t nr, bool even_cows);
void unmap_mapping_range(struct address_space *mapping,
loff_t const holebegin, loff_t const holelen, int even_cows);
+struct vm_area_struct *find_vma_without_flags(struct mm_struct *mm,
+ unsigned long addr, unsigned long len,
+ unsigned long prohibited_flags);
#else
static inline vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
unsigned long address, unsigned int flags)
diff --git a/mm/mremap.c b/mm/mremap.c
index 9a96cfc28675..dabae6a70287 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -430,14 +430,37 @@ static unsigned long move_vma(struct vm_area_struct *vma,
return new_addr;
}

+struct vm_area_struct *find_vma_without_flags(struct mm_struct *mm,
+ unsigned long addr, unsigned long len,
+ unsigned long prohibited_flags)
+{
+ struct vm_area_struct *vma = find_vma(mm, addr);
+
+ if (!vma || vma->vm_start > addr)
+ return ERR_PTR(-EFAULT);
+
+ /* vm area boundaries crossing */
+ if (len > vma->vm_end - addr)
+ return ERR_PTR(-EFAULT);
+
+ if (vma->vm_flags & prohibited_flags)
+ return ERR_PTR(-EFAULT);
+
+ return vma;
+}
+
static struct vm_area_struct *vma_to_resize(unsigned long addr,
unsigned long old_len, unsigned long new_len, unsigned long *p)
{
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma = find_vma(mm, addr);
- unsigned long pgoff;
+ struct vm_area_struct *vma;
+ unsigned long pgoff, prohibited_flags = VM_HUGETLB;

- if (!vma || vma->vm_start > addr)
+ if (old_len != new_len)
+ prohibited_flags |= VM_DONTEXPAND | VM_PFNMAP;
+
+ vma = find_vma_without_flags(mm, addr, old_len, prohibited_flags);
+ if (IS_ERR(vma))
return ERR_PTR(-EFAULT);

/*
@@ -453,13 +476,6 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
return ERR_PTR(-EINVAL);
}

- if (is_vm_hugetlb_page(vma))
- 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;

@@ -469,9 +485,6 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
return ERR_PTR(-EINVAL);

- if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
- return ERR_PTR(-EFAULT);
-
if (vma->vm_flags & VM_LOCKED) {
unsigned long locked, lock_limit;
locked = atomic64_read(&mm->locked_vm) << PAGE_SHIFT;