Description

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.

References 3

• git.kernel.org https://git.kernel.org/stable/c/7752d36343862323bbeea4ce3adf0ec2ed86e122
• git.kernel.org https://git.kernel.org/stable/c/a2c86aa621c22f2a7e26c654f936d65cfff0aa91
• git.kernel.org https://git.kernel.org/stable/c/f415e114b58fe02c41191e47f24bdabb438daf72

Remediation