CVE-2021-47579

In the Linux kernel, the following vulnerability has been resolved:

ovl: fix warning in ovl_create_real()

Syzbot triggered the following warning in ovl_workdir_create() -> ovl_create_real():

if (!err && WARN_ON(!newdentry->d_inode)) {

The reason is that the cgroup2 filesystem returns from mkdir without instantiating the new dentry.

Weird filesystems such as this will be rejected by overlayfs at a later stage during setup, but to prevent such a warning, call ovl_mkdir_real() directly from ovl_workdir_create() and reject this case early.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.