netdev - [PATCH bpf 2/2] selftests/bpf: test case for pointer null check in subprog

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Message-ID: <cc1b8cd3588b12701edd5a5177c47b52d27d3090.1555761008.git.paul.chaignon@orange.com>
Date:   Sat, 20 Apr 2019 14:40:24 +0200
From:   Paul Chaignon <paul.chaignon@...nge.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     Xiao Han <xiao.han@...nge.com>, Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>
Subject: [PATCH bpf 2/2] selftests/bpf: test case for pointer null check in
 subprog

This test case is equivalent to the following pseudo-code.  It checks that
the verifier does not complain on line 6 and recognizes that ptr isn't
null.

1: ptr = bpf_map_lookup_elem(map, &key);
2: ret = subprog(ptr) {
3:   return ptr != NULL;
4: }
5: if (ret)
6:   value = *ptr;

Signed-off-by: Paul Chaignon <paul.chaignon@...nge.com>
---
 tools/testing/selftests/bpf/verifier/calls.c | 25 ++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/tools/testing/selftests/bpf/verifier/calls.c b/tools/testing/selftests/bpf/verifier/calls.c
index fb11240b758b..9093a8f64dc6 100644
--- a/tools/testing/selftests/bpf/verifier/calls.c
+++ b/tools/testing/selftests/bpf/verifier/calls.c
@@ -374,6 +374,31 @@
 	.prog_type = BPF_PROG_TYPE_XDP,
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },
+{
+	"calls: ptr null check in subprog",
+	.insns = {
+	BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+	BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 3),
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+	BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_6, 0),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 1),
+	BPF_MOV64_IMM(BPF_REG_0, 1),
+	BPF_EXIT_INSN(),
+	},
+	.errstr_unpriv = "function calls to other bpf functions are allowed for root only",
+	.fixup_map_hash_48b = { 3 },
+	.result_unpriv = REJECT,
+	.result = ACCEPT,
+	.retval = 0,
+},
 {
 	"calls: two calls with args",
 	.insns = {
-- 
2.17.1