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-rw-r--r--mm/userfaultfd.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 96d9eae5c7..2213d887ec 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -312,7 +312,7 @@ static int mfill_atomic_pte_poison(pmd_t *dst_pmd,
ret = -EEXIST;
/* Refuse to overwrite any PTE, even a PTE marker (e.g. UFFD WP). */
- if (!pte_none(*dst_pte))
+ if (!pte_none(ptep_get(dst_pte)))
goto out_unlock;
set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
@@ -357,6 +357,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(
unsigned long dst_start,
unsigned long src_start,
unsigned long len,
+ atomic_t *mmap_changing,
uffd_flags_t flags)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
@@ -472,6 +473,15 @@ retry:
goto out;
}
mmap_read_lock(dst_mm);
+ /*
+ * If memory mappings are changing because of non-cooperative
+ * operation (e.g. mremap) running in parallel, bail out and
+ * request the user to retry later
+ */
+ if (mmap_changing && atomic_read(mmap_changing)) {
+ err = -EAGAIN;
+ break;
+ }
dst_vma = NULL;
goto retry;
@@ -506,6 +516,7 @@ extern ssize_t mfill_atomic_hugetlb(struct vm_area_struct *dst_vma,
unsigned long dst_start,
unsigned long src_start,
unsigned long len,
+ atomic_t *mmap_changing,
uffd_flags_t flags);
#endif /* CONFIG_HUGETLB_PAGE */
@@ -622,8 +633,8 @@ retry:
* If this is a HUGETLB vma, pass off to appropriate routine
*/
if (is_vm_hugetlb_page(dst_vma))
- return mfill_atomic_hugetlb(dst_vma, dst_start,
- src_start, len, flags);
+ return mfill_atomic_hugetlb(dst_vma, dst_start, src_start,
+ len, mmap_changing, flags);
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
goto out_unlock;