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.
CVSS Details
- CVSS 3.1 Base Score: 4.7
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H)
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