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Diffstat (limited to 'mm/userfaultfd.c')
-rw-r--r--mm/userfaultfd.c62
1 files changed, 46 insertions, 16 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 5029f241908f..458acda96f20 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -33,6 +33,8 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
void *page_kaddr;
int ret;
struct page *page;
+ pgoff_t offset, max_off;
+ struct inode *inode;
if (!*pagep) {
ret = -ENOMEM;
@@ -48,7 +50,7 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
/* fallback to copy_from_user outside mmap_sem */
if (unlikely(ret)) {
- ret = -EFAULT;
+ ret = -ENOENT;
*pagep = page;
/* don't free the page */
goto out;
@@ -73,8 +75,17 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
if (dst_vma->vm_flags & VM_WRITE)
_dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
- ret = -EEXIST;
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+ if (dst_vma->vm_file) {
+ /* the shmem MAP_PRIVATE case requires checking the i_size */
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ ret = -EFAULT;
+ if (unlikely(offset >= max_off))
+ goto out_release_uncharge_unlock;
+ }
+ ret = -EEXIST;
if (!pte_none(*dst_pte))
goto out_release_uncharge_unlock;
@@ -108,11 +119,22 @@ static int mfill_zeropage_pte(struct mm_struct *dst_mm,
pte_t _dst_pte, *dst_pte;
spinlock_t *ptl;
int ret;
+ pgoff_t offset, max_off;
+ struct inode *inode;
_dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
dst_vma->vm_page_prot));
- ret = -EEXIST;
dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
+ if (dst_vma->vm_file) {
+ /* the shmem MAP_PRIVATE case requires checking the i_size */
+ inode = dst_vma->vm_file->f_inode;
+ offset = linear_page_index(dst_vma, dst_addr);
+ max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+ ret = -EFAULT;
+ if (unlikely(offset >= max_off))
+ goto out_unlock;
+ }
+ ret = -EEXIST;
if (!pte_none(*dst_pte))
goto out_unlock;
set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
@@ -205,8 +227,9 @@ retry:
if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
goto out_unlock;
/*
- * Only allow __mcopy_atomic_hugetlb on userfaultfd
- * registered ranges.
+ * Check the vma is registered in uffd, this is
+ * required to enforce the VM_MAYWRITE check done at
+ * uffd registration time.
*/
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
@@ -274,7 +297,7 @@ retry:
cond_resched();
- if (unlikely(err == -EFAULT)) {
+ if (unlikely(err == -ENOENT)) {
up_read(&dst_mm->mmap_sem);
BUG_ON(!page);
@@ -380,7 +403,17 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
{
ssize_t err;
- if (vma_is_anonymous(dst_vma)) {
+ /*
+ * The normal page fault path for a shmem will invoke the
+ * fault, fill the hole in the file and COW it right away. The
+ * result generates plain anonymous memory. So when we are
+ * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
+ * generate anonymous memory directly without actually filling
+ * the hole. For the MAP_PRIVATE case the robustness check
+ * only happens in the pagetable (to verify it's still none)
+ * and not in the radix tree.
+ */
+ if (!(dst_vma->vm_flags & VM_SHARED)) {
if (!zeropage)
err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
dst_addr, src_addr, page);
@@ -449,13 +482,9 @@ retry:
if (!dst_vma)
goto out_unlock;
/*
- * Be strict and only allow __mcopy_atomic on userfaultfd
- * registered ranges to prevent userland errors going
- * unnoticed. As far as the VM consistency is concerned, it
- * would be perfectly safe to remove this check, but there's
- * no useful usage for __mcopy_atomic ouside of userfaultfd
- * registered ranges. This is after all why these are ioctls
- * belonging to the userfaultfd and not syscalls.
+ * Check the vma is registered in uffd, this is required to
+ * enforce the VM_MAYWRITE check done at uffd registration
+ * time.
*/
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
@@ -489,7 +518,8 @@ retry:
* dst_vma.
*/
err = -ENOMEM;
- if (vma_is_anonymous(dst_vma) && unlikely(anon_vma_prepare(dst_vma)))
+ if (!(dst_vma->vm_flags & VM_SHARED) &&
+ unlikely(anon_vma_prepare(dst_vma)))
goto out_unlock;
while (src_addr < src_start + len) {
@@ -530,7 +560,7 @@ retry:
src_addr, &page, zeropage);
cond_resched();
- if (unlikely(err == -EFAULT)) {
+ if (unlikely(err == -ENOENT)) {
void *page_kaddr;
up_read(&dst_mm->mmap_sem);