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Change History

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.

https://git.kernel.org/stable/c/7752d36343862323bbeea4ce3adf0ec2ed86e122

https://git.kernel.org/stable/c/a2c86aa621c22f2a7e26c654f936d65cfff0aa91

https://git.kernel.org/stable/c/f415e114b58fe02c41191e47f24bdabb438daf72