The issue is related to a memory leak in the Linux kernel, specifically in the s390/iucv component. When the MSG PEEK flag is passed to `skb recv datagram()`, it increments the `skb->users` refcount, but `iucv sock recvmsg()` does not decrement the refcount at exit. This results in a memory leak in `skb queue purge()` and a WARN ON in `iucv sock destruct()` during socket close. The estimated number of potentially affected devices worldwide is not available. There is no information about real-world incidents where this issue was exploited.
Technical details about exploitation include:
- The `MSG PEEK` flag is used in the `skb recv datagram()` function.
- The `skb->users` refcount is incremented when the `MSG PEEK` flag is passed.
- The `iucv sock recvmsg()` function does not decrement the `skb->users` refcount at exit.
- The memory leak occurs in `skb queue purge()`.
- A WARN ON is triggered in `iucv sock destruct()` during socket close.