netdev - [PATCH bpf-next] selftests/bpf: Add a testcase for 64-bit bounds propagation issue.

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Message-Id: <20211029172216.88408-1-alexei.starovoitov@gmail.com>
Date:   Fri, 29 Oct 2021 10:22:16 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     davem@...emloft.net
Cc:     daniel@...earbox.net, andrii@...nel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH bpf-next] selftests/bpf: Add a testcase for 64-bit bounds propagation issue.

From: Alexei Starovoitov <ast@...nel.org>

./test_progs-no_alu32 -vv -t twfw

Before the fix:
19: (25) if r1 > 0x3f goto pc+6
 R1_w=inv(id=0,umax_value=63,var_off=(0x0; 0xff),s32_max_value=255,u32_max_value=255)

and eventually:

invalid access to map value, value_size=8 off=7 size=8
R6 max value is outside of the allowed memory range
libbpf: failed to load object 'no_alu32/twfw.o'

After the fix:
19: (25) if r1 > 0x3f goto pc+6
 R1_w=inv(id=0,umax_value=63,var_off=(0x0; 0x3f))

verif_twfw:OK

Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
 .../bpf/prog_tests/bpf_verif_scale.c          |  5 ++
 tools/testing/selftests/bpf/progs/twfw.c      | 58 +++++++++++++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/twfw.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
index 867349e4ed9e..27f5d8ea7964 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
@@ -202,3 +202,8 @@ void test_verif_scale_seg6_loop()
 {
 	scale_test("test_seg6_loop.o", BPF_PROG_TYPE_LWT_SEG6LOCAL, false);
 }
+
+void test_verif_twfw()
+{
+	scale_test("twfw.o", BPF_PROG_TYPE_CGROUP_SKB, false);
+}
diff --git a/tools/testing/selftests/bpf/progs/twfw.c b/tools/testing/selftests/bpf/progs/twfw.c
new file mode 100644
index 000000000000..de1b18a62b46
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/twfw.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <linux/types.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/bpf.h>
+#include <stdint.h>
+
+#define TWFW_MAX_TIERS (64)
+/*
+ * load is successful
+ * #define TWFW_MAX_TIERS (64u)$
+ */
+
+struct twfw_tier_value {
+	unsigned long mask[1];
+};
+
+struct rule {
+	uint8_t seqnum;
+};
+
+struct rules_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, __u32);
+	__type(value, struct rule);
+	__uint(max_entries, 1);
+};
+
+struct tiers_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, __u32);
+	__type(value, struct twfw_tier_value);
+	__uint(max_entries, 1);
+};
+
+struct rules_map rules SEC(".maps");
+struct tiers_map tiers SEC(".maps");
+
+SEC("cgroup_skb/ingress")
+int twfw_verifier(struct __sk_buff* skb)
+{
+	const uint32_t key = 0;
+	const struct twfw_tier_value* tier = bpf_map_lookup_elem(&tiers, &key);
+	if (!tier)
+		return 1;
+
+	struct rule* rule = bpf_map_lookup_elem(&rules, &key);
+	if (!rule)
+		return 1;
+
+	if (rule && rule->seqnum < TWFW_MAX_TIERS) {
+		/* rule->seqnum / 64 should always be 0 */
+		unsigned long mask = tier->mask[rule->seqnum / 64];
+		if (mask)
+			return 0;
+	}
+	return 1;
+}
-- 
2.30.2