Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
ovpn: fix use after free in unlock_ovpn()
unlock_ovpn() iterates over the release_list using llist_for_each_entry() and drops the peer reference inside the loop body via ovpn_peer_put().
If this drops the last reference, the peer is eventually freed. However, llist_for_each_entry() reads peer->release_entry.next in the loop advance expression, which runs after the body. By that time the peer may have already been freed, resulting in a use after free when advancing to the next list entry.
Fix this by using llist_for_each_entry_safe(), which caches the next pointer before executing the loop body.
Details
- Affected product:
- Debian 10 ELS
- Affected packages:
- linux @ 4.19.0