Security patch for CVE-2020-25212 breaks directory listings via 'ls' on NFS V4.2 shares mounted with selinux enabled labels

Solution Verified - Updated -

Issue

On any of our diskless systems that are running RHEL 7.9, with kernel "kernel-3.10.0-1160.11.1.el7.x86_64", Any share mounted via NFS V4.2 is broken. Our diskless nodes have SE Linux enabled, and are exporting SE Linux permissions as part of these NFS shares, which is why we need V4.2. When we run an "ls" command on a mounted NFS share, there are no results, so things like shell command tab completion do not work. However, if we run an ls command and specify a direct file on a mounted NFS share, it does show.

If we mount our NFS shares with an older NFS version, we are able to see our files. However, older NFS versions do not support SE Linux, therefore this is not a solution for us.

We believe that the change in the kernel for CVE-2020-25212 is the culprit here.
We reverted back to kernel-3.1.0-1160.6.1 and do not see this issue occur. We investigated further, and rolled back the changes to the two files listed in this CVE, and recompiled kernel-3.10.0-1160.11.1, and no longer see the issue.

Environment

  • Red Hat Enterprise Linux (NFS client)
  • NFS4.2 with selinux labels enabled
    • directory containing at least two entries with different selinux labels of differing lengths
  • kernels containing the patch for CVE-2020-25212
    • seen on kernel 3.10.0-1160.11.1.el7

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