bpf: enforce exact retval range on subprog/callback exit

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Instead of relying on potentially imprecise tnum representation of
expected return value range for callbacks and subprogs, validate that
smin/smax range satisfy exact expected range of return values.

E.g., if callback would need to return [0, 2] range, tnum can't
represent this precisely and instead will allow [0, 3] range. By
checking smin/smax range, we can make sure that subprog/callback indeed
returns only valid [0, 2] range.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231202175705.885270-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Andrii Nakryiko 2023-12-02 09:56:58 -08:00 • committed by Alexei Starovoitov

parent 0acd03a5bd

commit 8fa4ecd49b

2 changed files with 28 additions and 12 deletions

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7

include/linux/bpf_verifier.h

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33

kernel/bpf/verifier.c

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