fscrypt: destroy keyring after security_sb_delete()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: fscrypt: destroy keyring after security_sb_delete() fscrypt_destroy_keyring() must be called after all potentially-encrypted inodes were evicted; otherwise it cannot safely destroy the keyring. Since inodes that are in-use by the Landlock LSM don't get evicted until security_sb_delete(), this means that fscrypt_destroy_keyring() must be called *after* security_sb_delete(). This fixes a WARN_ON followed by a NULL dereference, only possible if Landlock was being used on encrypted files.

References

• https://git.kernel.org/stable/c/992a3f3e8a0c92151dfdf65fc85567c865fd558a
• https://git.kernel.org/stable/c/d77531fac6a1fd9f1db0195438ba5419d72b96c4
• https://git.kernel.org/stable/c/497ab5d9c7852dfedab2c9de75e41b60e54b7c5d
• https://git.kernel.org/stable/c/ccb820dc7d2236b1af0d54ae038a27b5b6d5ae5a