bpf: Reuse canonical string formatter for ctx errs

The array "reg_type_str" provides canonical formatting of register
types, however a couple of places would previously check whether a
register represented the context and write the name "context" directly.
An upcoming commit will add another pointer type to these statements, so
to provide more accurate error messages in the verifier, update these
error messages to use "reg_type_str" instead.

Signed-off-by: Joe Stringer <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>

Author: joestringer

kernel/bpf/verifier.c

@@ -1763,8 +1763,7 @@ static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_ins
 	if (is_ctx_reg(env, insn->dst_reg) ||
 	    is_pkt_reg(env, insn->dst_reg)) {
 		verbose(env, "BPF_XADD stores into R%d %s is not allowed\n",
-			insn->dst_reg, is_ctx_reg(env, insn->dst_reg) ?
-			"context" : "packet");
+			insn->dst_reg, reg_type_str[insn->dst_reg]);
 		return -EACCES;
 	}
 
@@ -4871,8 +4870,8 @@ static int do_check(struct bpf_verifier_env *env)
 				return err;
 
 			if (is_ctx_reg(env, insn->dst_reg)) {
-				verbose(env, "BPF_ST stores into R%d context is not allowed\n",
-					insn->dst_reg);
+				verbose(env, "BPF_ST stores into R%d %s is not allowed\n",
+					insn->dst_reg, reg_type_str[insn->dst_reg]);
 				return -EACCES;
 			}
 

tools/testing/selftests/bpf/test_verifier.c

@@ -3276,7 +3276,7 @@ static struct bpf_test tests[] = {
 			BPF_ST_MEM(BPF_DW, BPF_REG_1, offsetof(struct __sk_buff, mark), 0),
 			BPF_EXIT_INSN(),
 		},
-		.errstr = "BPF_ST stores into R1 context is not allowed",
+		.errstr = "BPF_ST stores into R1 inv is not allowed",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	},
@@ -3288,7 +3288,7 @@ static struct bpf_test tests[] = {
 				     BPF_REG_0, offsetof(struct __sk_buff, mark), 0),
 			BPF_EXIT_INSN(),
 		},
-		.errstr = "BPF_XADD stores into R1 context is not allowed",
+		.errstr = "BPF_XADD stores into R1 inv is not allowed",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	},
@@ -5266,7 +5266,7 @@ static struct bpf_test tests[] = {
 		.errstr_unpriv = "R2 leaks addr into mem",
 		.result_unpriv = REJECT,
 		.result = REJECT,
-		.errstr = "BPF_XADD stores into R1 context is not allowed",
+		.errstr = "BPF_XADD stores into R1 inv is not allowed",
 	},
 	{
 		"leak pointer into ctx 2",
@@ -5281,7 +5281,7 @@ static struct bpf_test tests[] = {
 		.errstr_unpriv = "R10 leaks addr into mem",
 		.result_unpriv = REJECT,
 		.result = REJECT,
-		.errstr = "BPF_XADD stores into R1 context is not allowed",
+		.errstr = "BPF_XADD stores into R1 inv is not allowed",
 	},
 	{
 		"leak pointer into ctx 3",
@@ -12230,7 +12230,7 @@ static struct bpf_test tests[] = {
 			BPF_EXIT_INSN(),
 		},
 		.result = REJECT,
-		.errstr = "BPF_XADD stores into R2 packet",
+		.errstr = "BPF_XADD stores into R2 ctx",
 		.prog_type = BPF_PROG_TYPE_XDP,
 	},
 	{