fix(agent): library-load probe reads d_name basename, not bpf_d_path (JEF-68)#22
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…(JEF-68)
The mmap_file (library-load) fentry was verifier-rejected on 6.8 ("helper call is not
allowed in probe"): bpf_d_path is only callable from hooks on the kernel's d_path
allowlist, and security_mmap_file isn't on it (security_file_open is, so secret-read is
fine). Best-effort attach masked it, so LibraryLoaded had never fired on these kernels —
leaving JEF-51's reachability correlation with no data.
Fix: keep the cheap PROT_EXEC filter on mmap_file, but read the library *name* — the leaf
dentry's d_name basename — directly via bpf_probe_read_kernel(_str) (allowed in any program
type) instead of bpf_d_path. Userspace already used only the basename, so no userspace
change. vmlinux already carries dentry/qstr (no BTF regen needed).
eBPF crate type-checks; the Linux Docker builder compiles+links the BPF object (EXIT 0).
The kernel verifier only runs on-node, so the real confirmation is the post-deploy attach
of mmap_file + LibraryLoaded events flowing.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VtjoJttCvBY4dzCoE4f9vP
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The
mmap_filelibrary-load probe was verifier-rejected on 6.8 —bpf_d_pathisn't allowed insecurity_mmap_file(not on the kernel's d_path allowlist;security_file_openis, so secret-read works). Best-effort attach masked it, soLibraryLoadednever fired → JEF-51 reachability had no data.Fix: keep the
PROT_EXECfilter, but read the leafdentry->d_namebasename viabpf_probe_read_kernel(allowed everywhere) instead ofbpf_d_path. Userspace already used only the basename → no userspace change; vmlinux already hasdentry/qstr.eBPF type-checks; Docker builder compiles+links (EXIT 0). Real gate is on-node: after deploy, confirm
mmap_fileattaches andLibraryLoadedevents flow.🤖 Generated with Claude Code