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

[Mike Rapoport <rppt@linux.vnet.ibm.com>]

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

Signed-off-by: Mike Rapoport <rppt@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

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