tracee-ebpf: turn MAX_PATH_COMPONENTS down to 48 #889
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Fixes: #851 For the kprobe security_sb_mount, the save_path_to_str_buf() complexity is too big with the unroll logic + MAX_PATH_COMPONENTS of 80, even on higher kernels (like 5.4 in Ubuntu). Reducing to 64 did NOT help. Reducing to 48 DID help and it worked. Ubuntu kernel contains c04c0d2b968a ("bpf: increase complexity limit and maximum program size") commit with no reversions. The commit states that: BPF_COMPLEXITY_LIMIT_INSNS is the kernel internal limit and success to load the program no longer depends on program size, but on 'smartness' of the verifier only. which might indicate that the eBPF verifier in older kernels, like 5.4, is not smart enough to consider an unroll of 80 iterations, in the path resolution function, a logic less complex than it should.
yanivagman
approved these changes
Aug 8, 2021
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Fixes: #851
For the kprobe security_sb_mount, the save_path_to_str_buf() complexity
is too big with the unroll logic + MAX_PATH_COMPONENTS of 80, even on
higher kernels (like 5.4 in Ubuntu). Reducing to 64 did NOT help.
Reducing to 48 DID help and it worked.
Ubuntu kernel contains c04c0d2b968a ("bpf: increase complexity limit and
maximum program size") commit with no reversions. The commit states
that:
which might indicate that the eBPF verifier in older kernels, like 5.4,
is not smart enough to consider an unroll of 80 iterations, in the path
resolution function, a logic less complex than it should.