[PATCH] userfaultfd_zeropage: return -ENOSPC in case mm has gone

[Mike Rapoport]

In the non-cooperative userfaultfd case, the process exit may race with
outstanding mcopy_atomic called by the uffd monitor.  Returning -ENOSPC
instead of -EINVAL when mm is already gone will allow uffd monitor to
distinguish this case from other error conditions.


Cc: sta...@vger.kernel.org
Fixes: 96333187ab162 ("userfaultfd_copy: return -ENOSPC in case mm has gone")

Signed-off-by: Mike Rapoport <r...@linux.vnet.ibm.com>
---

Unfortunately, I've overlooked userfaultfd_zeropage when I updated
userfaultd_copy :(

 fs/userfaultfd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index cadcd12a3d35..2d8c2d848668 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1643,6 +1643,8 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx 
*ctx,
                ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
                                     uffdio_zeropage.range.len);
                mmput(ctx->mm);
+       } else {
+               return -ENOSPC;
        }
        if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
                return -EFAULT;
-- 
2.7.4