linux-kernel - [PATCH v4 2/2] selftests/bpf: Add test for alu on PTR_TO_FLOW

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Date: Mon, 15 Jan 2024 09:20:28 +0100
From: Hao Sun <sunhao.th@...il.com>
To: bpf@...r.kernel.org
Cc: willemb@...gle.com,
	ast@...nel.org,
	andrii@...nel.org,
	daniel@...earbox.net,
	eddyz87@...il.com,
	yonghong.song@...ux.dev,
	linux-kernel@...r.kernel.org,
	Hao Sun <sunhao.th@...il.com>
Subject: [PATCH v4 2/2] selftests/bpf: Add test for alu on PTR_TO_FLOW_KEYS

Add a test case for PTR_TO_FLOW_KEYS alu. Testing if alu with
variable offset on flow_keys is rejected.

Signed-off-by: Hao Sun <sunhao.th@...il.com>
---
 .../bpf/progs/verifier_value_illegal_alu.c    | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
index 71814a753216..a9ab37d3b9e2 100644
--- a/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
+++ b/tools/testing/selftests/bpf/progs/verifier_value_illegal_alu.c
@@ -146,4 +146,23 @@ l0_%=:	exit;						\
 	: __clobber_all);
 }
 
+SEC("flow_dissector")
+__description("flow_keys illegal alu op with variable offset")
+__failure __msg("R7 pointer arithmetic on flow_keys prohibited")
+__naked void flow_keys_illegal_variable_offset_alu(void)
+{
+	asm volatile("					\
+	r6 = r1;					\
+	r7 = *(u64*)(r6 + %[flow_keys_off]);		\
+	r8 = 8;						\
+	r8 /= 1;					\
+	r8 &= 8;					\
+	r7 += r8;					\
+	r0 = *(u64*)(r7 + 0);				\
+	exit;						\
+"	:
+	: __imm_const(flow_keys_off, offsetof(struct __sk_buff, flow_keys))
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.34.1