bpf: teach verifier actual bounds of bpf_get_smp_processor_id() result

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bpf_get_smp_processor_id() helper returns current CPU on which BPF
program runs. It can't return value that is bigger than maximum allowed
number of CPUs (minus one, due to zero indexing). Teach BPF verifier to
recognize that. This makes it possible to use bpf_get_smp_processor_id()
result to index into arrays without extra checks, as demonstrated in
subsequent selftests/bpf patch.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230711232400.1658562-1-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Andrii Nakryiko 2023-07-11 16:23:59 -07:00 • committed by Alexei Starovoitov

parent 87e098e623

commit f42bcd168d

1 changed files with 26 additions and 11 deletions

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kernel/bpf/verifier.c

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