move_vma() can't just return if f_op->mremap() fails, we should
unmap the new vma like we do if move_page_tables() fails. To avoid
the code duplication this patch moves the "move entries back" under
the new "if (err)" branch.

Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: David Rientjes <[email protected]>
---
 mm/mremap.c |   16 +++++++---------
 1 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index a7c93ec..f54a43f 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -276,6 +276,12 @@ static unsigned long move_vma(struct vm_area_struct *vma,
        moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
                                     need_rmap_locks);
        if (moved_len < old_len) {
+               err = -ENOMEM;
+       } else if (vma->vm_file && vma->vm_file->f_op->mremap) {
+               err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
+       }
+
+       if (unlikely(err)) {
                /*
                 * On error, move entries back from new area to old,
                 * which will succeed since page tables still there,
@@ -286,16 +292,8 @@ static unsigned long move_vma(struct vm_area_struct *vma,
                vma = new_vma;
                old_len = new_len;
                old_addr = new_addr;
-               new_addr = -ENOMEM;
+               new_addr = err;
        } else {
-               if (vma->vm_file && vma->vm_file->f_op->mremap) {
-                       err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
-                       if (err < 0) {
-                               move_page_tables(new_vma, new_addr, vma,
-                                                old_addr, moved_len, true);
-                               return err;
-                       }
-               }
                arch_remap(mm, old_addr, old_addr + old_len,
                           new_addr, new_addr + new_len);
        }
-- 
1.5.5.1

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