bpf: Move check_ptr_off_reg before check_map_access

Some functions in next patch want to use this function, and those
functions will be called by check_map_access, hence move it before
check_map_access.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Joanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/bpf/20220415160354.1050687-3-memxor@gmail.com

Author: kkdwvd

kernel/bpf/verifier.c

@@ -3469,6 +3469,44 @@ static int check_mem_region_access(struct bpf_verifier_env *env, u32 regno,
 	return 0;
 }
 
+static int __check_ptr_off_reg(struct bpf_verifier_env *env,
+			       const struct bpf_reg_state *reg, int regno,
+			       bool fixed_off_ok)
+{
+	/* Access to this pointer-typed register or passing it to a helper
+	 * is only allowed in its original, unmodified form.
+	 */
+
+	if (reg->off < 0) {
+		verbose(env, "negative offset %s ptr R%d off=%d disallowed\n",
+			reg_type_str(env, reg->type), regno, reg->off);
+		return -EACCES;
+	}
+
+	if (!fixed_off_ok && reg->off) {
+		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
+			reg_type_str(env, reg->type), regno, reg->off);
+		return -EACCES;
+	}
+
+	if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
+		char tn_buf[48];
+
+		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
+		verbose(env, "variable %s access var_off=%s disallowed\n",
+			reg_type_str(env, reg->type), tn_buf);
+		return -EACCES;
+	}
+
+	return 0;
+}
+
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno)
+{
+	return __check_ptr_off_reg(env, reg, regno, false);
+}
+
 /* check read/write into a map element with possible variable offset */
 static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 			    int off, int size, bool zero_size_allowed)
@@ -3980,44 +4018,6 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
-static int __check_ptr_off_reg(struct bpf_verifier_env *env,
-			       const struct bpf_reg_state *reg, int regno,
-			       bool fixed_off_ok)
-{
-	/* Access to this pointer-typed register or passing it to a helper
-	 * is only allowed in its original, unmodified form.
-	 */
-
-	if (reg->off < 0) {
-		verbose(env, "negative offset %s ptr R%d off=%d disallowed\n",
-			reg_type_str(env, reg->type), regno, reg->off);
-		return -EACCES;
-	}
-
-	if (!fixed_off_ok && reg->off) {
-		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
-			reg_type_str(env, reg->type), regno, reg->off);
-		return -EACCES;
-	}
-
-	if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
-		char tn_buf[48];
-
-		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
-		verbose(env, "variable %s access var_off=%s disallowed\n",
-			reg_type_str(env, reg->type), tn_buf);
-		return -EACCES;
-	}
-
-	return 0;
-}
-
-int check_ptr_off_reg(struct bpf_verifier_env *env,
-		      const struct bpf_reg_state *reg, int regno)
-{
-	return __check_ptr_off_reg(env, reg, regno, false);
-}
-
 static int __check_buffer_access(struct bpf_verifier_env *env,
 				 const char *buf_info,
 				 const struct bpf_reg_state *reg,