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When the following sequence of instructions is processed: 1: ... rX setup with [negative, positive] bounds ... 2: if rX == 0 goto ... 3: if rX > C goto ... 4: ... code relying on rX being in range [1, C] ... The cnum-based implementation only infers that rX range is [0, C] at instruction (4). The pre-cnum signed/unsigned ranges based representation could always deduct from 'rX != 0' that umin bound is 1. This patch introduces a workaround forking the verifier state when a register with sign-crossing range is compared to zero. [1] https://lore.kernel.org/bpf/96c4a1aa4333d10b882a9b5093d2d982f9f106e3.camel@gmail.com/T/ --- Eduard Zingerman (2): bpf: fork state when comparing sign crossing ranges with zero selftests/bpf: test fork on zero comparison with wrapping ranges kernel/bpf/verifier.c | 71 ++++++++++++++++++++++ .../testing/selftests/bpf/progs/verifier_bounds.c | 68 +++++++++++++++++++++ 2 files changed, 139 insertions(+) --- base-commit: e42e53ae23b7d41df22ccd7788192bf578f24da2 change-id: 20260529-cnum-split-at-zero-3c03db9234d3