linux-kernel - [PATCH 2/2] bpf, selftests: Add verifier test case for ALU64

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Date:   Wed, 10 Aug 2022 18:09:19 +0800
From:   Youlin Li <liulin063@...il.com>
To:     daniel@...earbox.net, haoluo@...gle.com
Cc:     ast@...nel.org, john.fastabend@...il.com, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        kpsingh@...nel.org, sdf@...gle.com, jolsa@...nel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Youlin Li <liulin063@...il.com>
Subject: [PATCH 2/2] bpf, selftests: Add verifier test case for ALU64

Add a test case to ensure that 32-bit bounds can be learned from 64-bit
bounds when performing 64-bit ALU operations.

Make use of dead code elimination, so that we can see the verifier
bailing out on unmodified kernels.

Before:
    ./test_verifier 165
    #165/p 32-bit bounds update in ALU64 FAIL
    Failed to load prog 'Permission denied'!
    R2 !read_ok
    verification time 49 usec
    stack depth 0
    processed 8 insns (limit 1000000) max_states_per_insn 0 total_states
    0 peak_states 0 mark_read 0
    Summary: 0 PASSED, 1 SKIPPED, 1 FAILED

After:
    ./test_verifier 165
    #165/p 32-bit bounds update in ALU64 OK
    Summary: 1 PASSED, 1 SKIPPED, 0 FAILED

Signed-off-by: Youlin Li <liulin063@...il.com>
---
 tools/testing/selftests/bpf/verifier/bounds.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/tools/testing/selftests/bpf/verifier/bounds.c b/tools/testing/selftests/bpf/verifier/bounds.c
index 33125d5f6772..b9aee2f2c66e 100644
--- a/tools/testing/selftests/bpf/verifier/bounds.c
+++ b/tools/testing/selftests/bpf/verifier/bounds.c
@@ -753,3 +753,20 @@
 	.result_unpriv = REJECT,
 	.result = ACCEPT,
 },
+{
+	"32-bit bounds update in ALU64",
+	.insns = {
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_MOV64_IMM(BPF_REG_1, 0),
+	BPF_ALU64_IMM(BPF_NEG, BPF_REG_1, 0),
+	BPF_ALU64_IMM(BPF_NEG, BPF_REG_1, 0),
+	BPF_ALU64_IMM(BPF_ARSH, BPF_REG_1, 63),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 2),
+	BPF_JMP32_IMM(BPF_JGE, BPF_REG_1, 1, 1),
+	BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
+	BPF_JMP32_IMM(BPF_JLE, BPF_REG_1, 2, 1),
+	BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
+	BPF_EXIT_INSN()
+	},
+	.result = ACCEPT,
+},
-- 
2.25.1