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-rw-r--r--tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c70
1 files changed, 70 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 5905e036e0ea..a955a6358206 100644
--- a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
+++ b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
@@ -239,4 +239,74 @@ int bpf_loop_iter_limit_nested(void *unused)
return 1000 * a + b + c;
}
+struct iter_limit_bug_ctx {
+ __u64 a;
+ __u64 b;
+ __u64 c;
+};
+
+static __naked void iter_limit_bug_cb(void)
+{
+ /* This is the same as C code below, but written
+ * in assembly to control which branches are fall-through.
+ *
+ * switch (bpf_get_prandom_u32()) {
+ * case 1: ctx->a = 42; break;
+ * case 2: ctx->b = 42; break;
+ * default: ctx->c = 42; break;
+ * }
+ */
+ asm volatile (
+ "r9 = r2;"
+ "call %[bpf_get_prandom_u32];"
+ "r1 = r0;"
+ "r2 = 42;"
+ "r0 = 0;"
+ "if r1 == 0x1 goto 1f;"
+ "if r1 == 0x2 goto 2f;"
+ "*(u64 *)(r9 + 16) = r2;"
+ "exit;"
+ "1: *(u64 *)(r9 + 0) = r2;"
+ "exit;"
+ "2: *(u64 *)(r9 + 8) = r2;"
+ "exit;"
+ :
+ : __imm(bpf_get_prandom_u32)
+ : __clobber_all
+ );
+}
+
+SEC("tc")
+__failure
+__flag(BPF_F_TEST_STATE_FREQ)
+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);
+
+ /* This is the same as C code below,
+ * written in assembly to guarantee checks order.
+ *
+ * if (ctx.a == 42 && ctx.b == 42 && ctx.c == 7)
+ * asm volatile("r1 /= 0;":::"r1");
+ */
+ asm volatile (
+ "r1 = *(u64 *)%[ctx_a];"
+ "if r1 != 42 goto 1f;"
+ "r1 = *(u64 *)%[ctx_b];"
+ "if r1 != 42 goto 1f;"
+ "r1 = *(u64 *)%[ctx_c];"
+ "if r1 != 7 goto 1f;"
+ "r1 /= 0;"
+ "1:"
+ :
+ : [ctx_a]"m"(ctx.a),
+ [ctx_b]"m"(ctx.b),
+ [ctx_c]"m"(ctx.c)
+ : "r1"
+ );
+ return 0;
+}
+
char _license[] SEC("license") = "GPL";