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Fri, 29 May 2026 01:13:34 -0700 (PDT) Received: from badger ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2bf239e6f57sm10806715ad.13.2026.05.29.01.13.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 May 2026 01:13:34 -0700 (PDT) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, yonghong.song@linux.dev, zhuyifei@google.com, Eduard Zingerman Subject: [PATCH bpf 2/2] selftests/bpf: test fork on zero comparison with wrapping ranges Date: Fri, 29 May 2026 01:13:20 -0700 Message-ID: <20260529-cnum-split-at-zero-v1-2-986c03752226@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260529-cnum-split-at-zero-v1-0-986c03752226@gmail.com> References: <20260529-cnum-split-at-zero-v1-0-986c03752226@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Add tests verifying that the verifier correctly narrows a sign-boundary-crossing range after comparing with zero. - fork_on_zero_cmp_k - BPF_K conditional instruction; - fork_on_zero_cmp_x - BPF_X conditional instruction with src being zero. - fork_on_zero_cmp_x_swapped - BPF_X conditional instruction with dst being zero. Signed-off-by: Eduard Zingerman --- .../testing/selftests/bpf/progs/verifier_bounds.c | 68 ++++++++++++++++++++++ 1 file changed, 68 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_bounds.c b/tools/testing/selftests/bpf/progs/verifier_bounds.c index bc038ac2df98..f97b0e109326 100644 --- a/tools/testing/selftests/bpf/progs/verifier_bounds.c +++ b/tools/testing/selftests/bpf/progs/verifier_bounds.c @@ -2294,4 +2294,72 @@ __naked void range_within_cnum_cross_both_boundaries(void) : __clobber_all); } +SEC("socket") +__success +__naked void fork_on_zero_cmp_k(void) +{ + asm volatile (" \ + call %[bpf_get_prandom_u32]; \ + r0 &= 0xff; /* r0 ∈ [0, 255] */ \ + r1 = 8; \ + r1 -= r0; /* r1 ∈ [-247, 8] */ \ + if r1 == 0 goto 1f; \ + if r1 > 8 goto 1f; /* r1 ∈ [1, 8] */ \ + if r1 < 1 goto 2f; /* must be dead */ \ + if r1 > 8 goto 2f; /* must be dead */ \ + goto 1f; \ +2: r0 /= 0; /* unreachable */ \ +1: r0 = 0; \ + exit; \ + " + :: __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +SEC("socket") +__success +__naked void fork_on_zero_cmp_x(void) +{ + asm volatile (" \ + call %[bpf_get_prandom_u32]; \ + r0 &= 0xff; /* r0 ∈ [0, 255] */ \ + r1 = 8; \ + r1 -= r0; /* r1 ∈ [-247, 8] */ \ + r2 = 0; \ + if r1 == r2 goto 1f; \ + if r1 > 8 goto 1f; /* r1 ∈ [1, 8] */ \ + if r1 < 1 goto 2f; /* must be dead */ \ + if r1 > 8 goto 2f; /* must be dead */ \ + goto 1f; \ +2: r0 /= 0; /* unreachable */ \ +1: r0 = 0; \ + exit; \ + " + :: __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +SEC("socket") +__success +__naked void fork_on_zero_cmp_x_swapped(void) +{ + asm volatile (" \ + call %[bpf_get_prandom_u32]; \ + r0 &= 0xff; /* r0 ∈ [0, 255] */ \ + r1 = 8; \ + r1 -= r0; /* r1 ∈ [-247, 8] */ \ + r2 = 0; \ + if r2 == r1 goto 1f; \ + if r1 > 8 goto 1f; /* r1 ∈ [1, 8] */ \ + if r1 < 1 goto 2f; /* must be dead */ \ + if r1 > 8 goto 2f; /* must be dead */ \ + goto 1f; \ +2: r0 /= 0; /* unreachable */ \ +1: r0 = 0; \ + exit; \ + " + :: __imm(bpf_get_prandom_u32) + : __clobber_all); +} + char _license[] SEC("license") = "GPL"; -- 2.53.0