[PATCH 3.10 79/80] do_last(): dont let a bogus return value from ->open() et.al. to confuse us

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <v...@zeniv.linux.org.uk>

commit c80567c82ae4814a41287618e315a60ecf513be6 upstream.

... into returning a positive to path_openat(), which would interpret that
as "symlink had been encountered" and proceed to corrupt memory, etc.
It can only happen due to a bug in some ->open() instance or in some LSM
hook, etc., so we report any such event *and* make sure it doesn't trick
us into further unpleasantness.

Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/namei.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2917,6 +2917,10 @@ opened:
                        goto exit_fput;
        }
 out:
+       if (unlikely(error > 0)) {
+               WARN_ON(1);
+               error = -EINVAL;
+       }
        if (got_write)
                mnt_drop_write(nd->path.mnt);
        path_put(&save_parent);