userfaultfd: mcopy_atomic: return -ENOENT when no compatible VMA found
The memory mapping of a process may change between #PF event and the
call to mcopy_atomic that comes to resolve the page fault. In such
case, there will be no VMA covering the range passed to mcopy_atomic or
the VMA will not have userfaultfd context.
To allow uffd monitor to distinguish those case from other errors, let's
return -ENOENT instead of -EINVAL.
Note, that despite availability of UFFD_EVENT_UNMAP there still might be
race between the processing of UFFD_EVENT_UNMAP and outstanding
mcopy_atomic in case of non-cooperative uffd usage.
[rppt@linux.vnet.ibm.com: update cases returning -ENOENT]
Link: http://lkml.kernel.org/r/20170207150249.GA6709@rapoport-lnx
[aarcange@redhat.com: merge fix]
[akpm@linux-foundation.org: fix the merge fix]
Link: http://lkml.kernel.org/r/1485542673-24387-5-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 1e5c2f9..9f0ad2a 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -197,22 +197,25 @@
* retry, dst_vma will be set to NULL and we must lookup again.
*/
if (!dst_vma) {
- err = -EINVAL;
+ err = -ENOENT;
dst_vma = find_vma(dst_mm, dst_start);
if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
goto out_unlock;
-
- if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
+ /*
+ * Only allow __mcopy_atomic_hugetlb on userfaultfd
+ * registered ranges.
+ */
+ if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
- /*
- * Make sure the remaining dst range is both valid and
- * fully within a single existing vma.
- */
if (dst_start < dst_vma->vm_start ||
dst_start + len > dst_vma->vm_end)
goto out_unlock;
+ err = -EINVAL;
+ if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
+ goto out_unlock;
+
vm_shared = dst_vma->vm_flags & VM_SHARED;
}
@@ -221,12 +224,6 @@
goto out_unlock;
/*
- * Only allow __mcopy_atomic_hugetlb on userfaultfd registered ranges.
- */
- if (!dst_vma->vm_userfaultfd_ctx.ctx)
- goto out_unlock;
-
- /*
* If not shared, ensure the dst_vma has a anon_vma.
*/
err = -ENOMEM;
@@ -404,30 +401,11 @@
* Make sure the vma is not shared, that the dst range is
* both valid and fully within a single existing vma.
*/
- err = -EINVAL;
+ err = -ENOENT;
dst_vma = find_vma(dst_mm, dst_start);
if (!dst_vma)
goto out_unlock;
/*
- * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
- * it will overwrite vm_ops, so vma_is_anonymous must return false.
- */
- if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
- dst_vma->vm_flags & VM_SHARED))
- goto out_unlock;
-
- if (dst_start < dst_vma->vm_start ||
- dst_start + len > dst_vma->vm_end)
- goto out_unlock;
-
- /*
- * If this is a HUGETLB vma, pass off to appropriate routine
- */
- if (is_vm_hugetlb_page(dst_vma))
- return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
- src_start, len, zeropage);
-
- /*
* 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
@@ -439,6 +417,26 @@
if (!dst_vma->vm_userfaultfd_ctx.ctx)
goto out_unlock;
+ if (dst_start < dst_vma->vm_start ||
+ dst_start + len > dst_vma->vm_end)
+ goto out_unlock;
+
+ err = -EINVAL;
+ /*
+ * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
+ * it will overwrite vm_ops, so vma_is_anonymous must return false.
+ */
+ if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
+ dst_vma->vm_flags & VM_SHARED))
+ goto out_unlock;
+
+ /*
+ * If this is a HUGETLB vma, pass off to appropriate routine
+ */
+ if (is_vm_hugetlb_page(dst_vma))
+ return __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
+ src_start, len, zeropage);
+
if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
goto out_unlock;