bpf, verifier: fix register type dump in xadd and st

Using reg_type_str[insn->dst_reg] is incorrect since insn->dst_reg
contains the register number but not the actual register type. Add
a small reg_state() helper and use it to get to the type. Also fix
up the test_verifier test cases that have an incorrect errstr.

Fixes: 9d2be44a7f33 ("bpf: Reuse canonical string formatter for ctx errs")
Signed-off-by: Daniel Borkmann <[e-mail]>
Signed-off-by: Alexei Starovoitov <[e-mail]>

kernel/bpf/verifier.c

···
 	return reg->type != SCALAR_VALUE;
 }
 
+static struct bpf_reg_state *reg_state(struct bpf_verifier_env *env, int regno)
+{
+	return cur_regs(env) + regno;
+}
+
 static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
 {
-	return __is_pointer_value(env->allow_ptr_leaks, cur_regs(env) + regno);
+	return __is_pointer_value(env->allow_ptr_leaks, reg_state(env, regno));
 }
 
 static bool is_ctx_reg(struct bpf_verifier_env *env, int regno)
 {
-	const struct bpf_reg_state *reg = cur_regs(env) + regno;
+	const struct bpf_reg_state *reg = reg_state(env, regno);
 
 	return reg->type == PTR_TO_CTX ||
 	       reg->type == PTR_TO_SOCKET;
···
 
 static bool is_pkt_reg(struct bpf_verifier_env *env, int regno)
 {
-	const struct bpf_reg_state *reg = cur_regs(env) + regno;
+	const struct bpf_reg_state *reg = reg_state(env, regno);
 
 	return type_is_pkt_pointer(reg->type);
 }
···
 	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, reg_type_str[insn->dst_reg]);
+			insn->dst_reg,
+			reg_type_str[reg_state(env, insn->dst_reg)->type]);
 		return -EACCES;
 	}
 
···
 				int access_size, bool zero_size_allowed,
 				struct bpf_call_arg_meta *meta)
 {
-	struct bpf_reg_state *reg = cur_regs(env) + regno;
+	struct bpf_reg_state *reg = reg_state(env, regno);
 	struct bpf_func_state *state = func(env, reg);
 	int off, i, slot, spi;
 
···
 
 			if (is_ctx_reg(env, 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]);
+					insn->dst_reg,
+					reg_type_str[reg_state(env, insn->dst_reg)->type]);
 				return -EACCES;
 			}
 

tools/testing/selftests/bpf/test_verifier.c

···
 			BPF_ST_MEM(BPF_DW, BPF_REG_1, offsetof(struct __sk_buff, mark), 0),
 			BPF_EXIT_INSN(),
 		},
-		.errstr = "BPF_ST stores into R1 inv is not allowed",
+		.errstr = "BPF_ST stores into R1 ctx is not allowed",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	},
···
 				     BPF_REG_0, offsetof(struct __sk_buff, mark), 0),
 			BPF_EXIT_INSN(),
 		},
-		.errstr = "BPF_XADD stores into R1 inv is not allowed",
+		.errstr = "BPF_XADD stores into R1 ctx is not allowed",
 		.result = REJECT,
 		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 	},
···
 		.errstr_unpriv = "R2 leaks addr into mem",
 		.result_unpriv = REJECT,
 		.result = REJECT,
-		.errstr = "BPF_XADD stores into R1 inv is not allowed",
+		.errstr = "BPF_XADD stores into R1 ctx is not allowed",
 	},
 	{
 		"leak pointer into ctx 2",
···
 		.errstr_unpriv = "R10 leaks addr into mem",
 		.result_unpriv = REJECT,
 		.result = REJECT,
-		.errstr = "BPF_XADD stores into R1 inv is not allowed",
+		.errstr = "BPF_XADD stores into R1 ctx is not allowed",
 	},
 	{
 		"leak pointer into ctx 3",
···
 			BPF_EXIT_INSN(),
 		},
 		.result = REJECT,
-		.errstr = "BPF_XADD stores into R2 ctx",
+		.errstr = "BPF_XADD stores into R2 pkt is not allowed",
 		.prog_type = BPF_PROG_TYPE_XDP,
 	},
 	{