In the Linux kernel, the following vulnerability has been resolved:
bpf: Require frozen map for calculating map hash
Currently, bpf_map_get_info_by_fd calculates and caches the hash of the
map regardless of the map's frozen state.
This leads to a TOCTOU bug where userspace can call
BPF_OBJ_GET_INFO_BY_FD to cache the hash and then modify the map
contents before freezing.
Therefore, a trusted loader can be tricked into verifying the stale hash
while loading the modified contents.
Fix this by returning -EPERM if the map is not frozen when the hash is
requested. This ensures the hash is only generated for the final,
immutable state of the map.