netdev - [RFC bpf-next 02/11] bpf: Simplify ptr_min_max

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Date:   Wed,  9 May 2018 14:07:00 -0700
From:   Joe Stringer <joe@...d.net.nz>
To:     daniel@...earbox.net
Cc:     netdev@...r.kernel.org, ast@...nel.org, john.fastabend@...il.com,
        kafai@...com
Subject: [RFC bpf-next 02/11] bpf: Simplify ptr_min_max_vals adjustment

An upcoming commit will add another two pointer types that need very
similar behaviour, so generalise this function now.

Signed-off-by: Joe Stringer <joe@...d.net.nz>
---
 kernel/bpf/verifier.c                       | 22 ++++++++++------------
 tools/testing/selftests/bpf/test_verifier.c | 14 +++++++-------
 2 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f40e089c3893..a32b560072d7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2602,20 +2602,18 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		return -EACCES;
 	}
 
-	if (ptr_reg->type == PTR_TO_MAP_VALUE_OR_NULL) {
-		verbose(env, "R%d pointer arithmetic on PTR_TO_MAP_VALUE_OR_NULL prohibited, null-check it first\n",
-			dst);
-		return -EACCES;
-	}
-	if (ptr_reg->type == CONST_PTR_TO_MAP) {
-		verbose(env, "R%d pointer arithmetic on CONST_PTR_TO_MAP prohibited\n",
-			dst);
+	switch (ptr_reg->type) {
+	case PTR_TO_MAP_VALUE_OR_NULL:
+		verbose(env, "R%d pointer arithmetic on %s prohibited, null-check it first\n",
+			dst, reg_type_str[ptr_reg->type]);
 		return -EACCES;
-	}
-	if (ptr_reg->type == PTR_TO_PACKET_END) {
-		verbose(env, "R%d pointer arithmetic on PTR_TO_PACKET_END prohibited\n",
-			dst);
+	case CONST_PTR_TO_MAP:
+	case PTR_TO_PACKET_END:
+		verbose(env, "R%d pointer arithmetic on %s prohibited\n",
+			dst, reg_type_str[ptr_reg->type]);
 		return -EACCES;
+	default:
+		break;
 	}
 
 	/* In case of 'scalar += pointer', dst_reg inherits pointer type and id.
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 275b4570b5b8..53439f40e1de 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -3497,7 +3497,7 @@ static struct bpf_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 0),
 			BPF_EXIT_INSN(),
 		},
-		.errstr = "R3 pointer arithmetic on PTR_TO_PACKET_END",
+		.errstr = "R3 pointer arithmetic on pkt_end",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	},
@@ -4525,7 +4525,7 @@ static struct bpf_test tests[] = {
 			BPF_EXIT_INSN(),
 		},
 		.fixup_map1 = { 4 },
-		.errstr = "R4 pointer arithmetic on PTR_TO_MAP_VALUE_OR_NULL",
+		.errstr = "R4 pointer arithmetic on map_value_or_null",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS
 	},
@@ -4546,7 +4546,7 @@ static struct bpf_test tests[] = {
 			BPF_EXIT_INSN(),
 		},
 		.fixup_map1 = { 4 },
-		.errstr = "R4 pointer arithmetic on PTR_TO_MAP_VALUE_OR_NULL",
+		.errstr = "R4 pointer arithmetic on map_value_or_null",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS
 	},
@@ -4567,7 +4567,7 @@ static struct bpf_test tests[] = {
 			BPF_EXIT_INSN(),
 		},
 		.fixup_map1 = { 4 },
-		.errstr = "R4 pointer arithmetic on PTR_TO_MAP_VALUE_OR_NULL",
+		.errstr = "R4 pointer arithmetic on map_value_or_null",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS
 	},
@@ -6864,7 +6864,7 @@ static struct bpf_test tests[] = {
 			BPF_EXIT_INSN(),
 		},
 		.fixup_map_in_map = { 3 },
-		.errstr = "R1 pointer arithmetic on CONST_PTR_TO_MAP prohibited",
+		.errstr = "R1 pointer arithmetic on map_ptr prohibited",
 		.result = REJECT,
 	},
 	{
@@ -8538,7 +8538,7 @@ static struct bpf_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 0),
 			BPF_EXIT_INSN(),
 		},
-		.errstr = "R3 pointer arithmetic on PTR_TO_PACKET_END",
+		.errstr = "R3 pointer arithmetic on pkt_end",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_XDP,
 	},
@@ -8557,7 +8557,7 @@ static struct bpf_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 0),
 			BPF_EXIT_INSN(),
 		},
-		.errstr = "R3 pointer arithmetic on PTR_TO_PACKET_END",
+		.errstr = "R3 pointer arithmetic on pkt_end",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_XDP,
 	},
-- 
2.14.1