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5c2bc5e2 |
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22-Feb-2024 |
Eduard Zingerman <eddyz87@gmail.com> |
selftests/bpf: test case for callback_depth states pruning logic The test case was minimized from mailing list discussion [0]. It is equivalent to the following C program: struct iter_limit_bug_ctx { __u64 a; __u64 b; __u64 c; }; static __naked void iter_limit_bug_cb(void) { switch (bpf_get_prandom_u32()) { case 1: ctx->a = 42; break; case 2: ctx->b = 42; break; default: ctx->c = 42; break; } } int iter_limit_bug(struct __sk_buff *skb) { struct iter_limit_bug_ctx ctx = { 7, 7, 7 }; bpf_loop(2, iter_limit_bug_cb, &ctx, 0); if (ctx.a == 42 && ctx.b == 42 && ctx.c == 7) asm volatile("r1 /= 0;":::"r1"); return 0; } The main idea is that each loop iteration changes one of the state variables in a non-deterministic manner. Hence it is premature to prune the states that have two iterations left comparing them to states with one iteration left. E.g. {{7,7,7}, callback_depth=0} can reach state {42,42,7}, while {{7,7,7}, callback_depth=1} can't. [0] https://lore.kernel.org/bpf/9b251840-7cb8-4d17-bd23-1fc8071d8eef@linux.dev/ Acked-by: Yonghong Song <yonghong.song@linux.dev> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20240222154121.6991-3-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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57e2a52d |
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20-Nov-2023 |
Eduard Zingerman <eddyz87@gmail.com> |
selftests/bpf: check if max number of bpf_loop iterations is tracked Check that even if bpf_loop() callback simulation does not converge to a specific state, verification could proceed via "brute force" simulation of maximal number of callback calls. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20231121020701.26440-12-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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9f3330aa |
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20-Nov-2023 |
Eduard Zingerman <eddyz87@gmail.com> |
selftests/bpf: test widening for iterating callbacks A test case to verify that imprecise scalars widening is applied to callback entering state, when callback call is simulated repeatedly. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20231121020701.26440-10-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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958465e2 |
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20-Nov-2023 |
Eduard Zingerman <eddyz87@gmail.com> |
selftests/bpf: tests for iterating callbacks A set of test cases to check behavior of callback handling logic, check if verifier catches the following situations: - program not safe on second callback iteration; - program not safe on zero callback iterations; - infinite loop inside a callback. Verify that callback logic works for bpf_loop, bpf_for_each_map_elem, bpf_user_ringbuf_drain, bpf_find_vma. Acked-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20231121020701.26440-8-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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