bpf: Preserve unique-field state across nested structs

In the Linux kernel, the following vulnerability has been resolved: bpf: Preserve unique-field state across nested structs btf_find_struct_field() initializes a fresh seen mask for every recursive descent. Unique special fields in different levels of the same aggregate therefore do not see one another. The duplicate fields can reach btf_parse_fields(), where they trigger an invariant WARN_ON_ONCE(). A crafted user BTF can consequently trigger the warning before map creation checks capabilities. Initialize the seen mask once in btf_find_field() and pass the same pointer through struct, datasec, and nested-struct walks. This gives the entire field traversal one shared uniqueness state.

Source published

17 Sep 2026 16:10:24 UTC

Source modified

19 Oct 2026 09:04:21 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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