Verify fread(), fwrite(), and system() return values

These were starting to trigger compiler warning with recent glibc header
files and gcc.

src/eap_peer/eap_fast_pac.c

@@ -533,6 +533,8 @@ static void eap_fast_write(char **buf, char **pos, size_t *buf_len,
 static int eap_fast_write_pac(struct eap_sm *sm, const char *pac_file,
 			      char *buf, size_t len)
 {
+	int ret = 0;
+
 	if (os_strncmp(pac_file, "blob://", 7) == 0) {
 		struct wpa_config_blob *blob;
 		blob = os_zalloc(sizeof(*blob));
@@ -555,12 +557,16 @@ static int eap_fast_write_pac(struct eap_sm *sm, const char *pac_file,
 				   "file '%s' for writing", pac_file);
 			return -1;
 		}
-		fwrite(buf, 1, len, f);
+		if (fwrite(buf, 1, len, f) != len) {
+			wpa_printf(MSG_INFO, "EAP-FAST: Failed to write all "
+				   "PACs into '%s'", pac_file);
+			ret = -1;
+		}
 		os_free(buf);
 		fclose(f);
 	}
 
-	return 0;
+	return ret;
 }
 
 

src/utils/os_unix.c

@@ -220,7 +220,12 @@ char * os_readfile(const char *name, size_t *len)
 		return NULL;
 	}
 
-	fread(buf, 1, *len, f);
+	if (fread(buf, 1, *len, f) != *len) {
+		fclose(f);
+		free(buf);
+		return NULL;
+	}
+
 	fclose(f);
 
 	return buf;

wpa_supplicant/wpa_cli.c

@@ -1152,6 +1152,7 @@ static int wpa_cli_exec(const char *program, const char *arg1,
 	char *cmd;
 	size_t len;
 	int res;
+	int ret = 0;
 
 	len = os_strlen(program) + os_strlen(arg1) + os_strlen(arg2) + 3;
 	cmd = os_malloc(len);
@@ -1164,11 +1165,12 @@ static int wpa_cli_exec(const char *program, const char *arg1,
 	}
 	cmd[len - 1] = '\0';
 #ifndef _WIN32_WCE
-	system(cmd);
+	if (system(cmd) < 0)
+		ret = -1;
 #endif /* _WIN32_WCE */
 	os_free(cmd);
 
-	return 0;
+	return ret;
 }