CVE-2021-47579 Information

Description

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.

Reference

https://git.kernel.org/stable/c/445d2dc63e5871d218f21b8f62ab29ac72f2e6b8 https://git.kernel.org/stable/c/f9f300a92297be8250547347fd52216ef0177ae0 https://git.kernel.org/stable/c/6859985a2fbda5d1586bf44538853e1be69e85f7 https://git.kernel.org/stable/c/d2ccdd4e4efab06178608a34d7bfb20a54104c02 https://git.kernel.org/stable/c/1f5573cfe7a7056e80a92c7a037a3e69f3a13d1c