AZL-88662

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

bpf: fix end-of-list detection in cgroup_storage_get_next_key()

list_next_entry() never returns NULL -- when the current element is the last entry it wraps to the list head via container_of(). The subsequent NULL check is therefore dead code and get_next_key() never returns -ENOENT for the last element, instead reading storage->key from a bogus pointer that aliases internal map fields and copying the result to userspace.

Replace it with list_entry_is_head() so the function correctly returns -ENOENT when there are no more entries.