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authorEduard Zingerman <eddyz87@gmail.com>2023-11-21 05:07:01 +0300
committerAlexei Starovoitov <ast@kernel.org>2023-11-21 05:36:40 +0300
commit57e2a52deeb12ab84c15c6d0fb93638b5b94001b (patch)
tree807b0cdc43a76fe532c17fc31e96413c82161e1a /tools
parentbb124da69c47dd98d69361ec13244ece50bec63e (diff)
downloadlinux-57e2a52deeb12ab84c15c6d0fb93638b5b94001b.tar.xz
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>
Diffstat (limited to 'tools')
-rw-r--r--tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c75
1 files changed, 75 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
index 598c1e984b26..5905e036e0ea 100644
--- a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
+++ b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
@@ -164,4 +164,79 @@ int unsafe_find_vma(void *unused)
return choice_arr[loop_ctx.i];
}
+static int iter_limit_cb(__u32 idx, struct num_context *ctx)
+{
+ ctx->i++;
+ return 0;
+}
+
+SEC("?raw_tp")
+__success
+int bpf_loop_iter_limit_ok(void *unused)
+{
+ struct num_context ctx = { .i = 0 };
+
+ bpf_loop(1, iter_limit_cb, &ctx, 0);
+ return choice_arr[ctx.i];
+}
+
+SEC("?raw_tp")
+__failure __msg("invalid access to map value, value_size=2 off=2 size=1")
+int bpf_loop_iter_limit_overflow(void *unused)
+{
+ struct num_context ctx = { .i = 0 };
+
+ bpf_loop(2, iter_limit_cb, &ctx, 0);
+ return choice_arr[ctx.i];
+}
+
+static int iter_limit_level2a_cb(__u32 idx, struct num_context *ctx)
+{
+ ctx->i += 100;
+ return 0;
+}
+
+static int iter_limit_level2b_cb(__u32 idx, struct num_context *ctx)
+{
+ ctx->i += 10;
+ return 0;
+}
+
+static int iter_limit_level1_cb(__u32 idx, struct num_context *ctx)
+{
+ ctx->i += 1;
+ bpf_loop(1, iter_limit_level2a_cb, ctx, 0);
+ bpf_loop(1, iter_limit_level2b_cb, ctx, 0);
+ return 0;
+}
+
+/* Check that path visiting every callback function once had been
+ * reached by verifier. Variables 'ctx{1,2}i' below serve as flags,
+ * with each decimal digit corresponding to a callback visit marker.
+ */
+SEC("socket")
+__success __retval(111111)
+int bpf_loop_iter_limit_nested(void *unused)
+{
+ struct num_context ctx1 = { .i = 0 };
+ struct num_context ctx2 = { .i = 0 };
+ __u64 a, b, c;
+
+ bpf_loop(1, iter_limit_level1_cb, &ctx1, 0);
+ bpf_loop(1, iter_limit_level1_cb, &ctx2, 0);
+ a = ctx1.i;
+ b = ctx2.i;
+ /* Force 'ctx1.i' and 'ctx2.i' precise. */
+ c = choice_arr[(a + b) % 2];
+ /* This makes 'c' zero, but neither clang nor verifier know it. */
+ c /= 10;
+ /* Make sure that verifier does not visit 'impossible' states:
+ * enumerate all possible callback visit masks.
+ */
+ if (a != 0 && a != 1 && a != 11 && a != 101 && a != 111 &&
+ b != 0 && b != 1 && b != 11 && b != 101 && b != 111)
+ asm volatile ("r0 /= 0;" ::: "r0");
+ return 1000 * a + b + c;
+}
+
char _license[] SEC("license") = "GPL";