在/ data上创建文件时，AOSP权限被拒绝

debugcn 发表于 Dev

尼克1212

在Android 6.0中，我试图sample在/ data分区的文件夹中创建一个空文件：/data/sample/emptyfile。

该代码是从安装在以下库中的库运行的 /external

File file = new File(/data/sample/emptyfile);

try {
    file.createNewFile();
} catch (IOException e) {
    e.printStackTrace();
}

我已经sample在源上为文件夹分配了适当的权限/system/core/libcutils/fs_config.c

我尝试添加以下代码变体：

/* Rules for directories.
** These rules are applied based on "first match", so they
** should start with the most specific path and work their
** way up to the root.
*/

static const struct fs_path_config android_dirs[] = {
{ 00777, AID_ROOT, AID_ROOT,     0, "data/sample" },
{ 00770, AID_SYSTEM, AID_CACHE,  0, "cache" },
... etc.

并在：

/* Rules for files.
** These rules are applied based on "first match", so they
** should start with the most specific path and work their
** way up to the root. Prefixes ending in * denotes wildcard
** and will allow partial matches.
*/
static const char conf_dir[] = "/system/etc/fs_config_dirs";
static const char conf_file[] = "/system/etc/fs_config_files";

static const struct fs_path_config android_files[] = {
    { 00777, AID_ROOT,      AID_ROOT,      0, "data/sample/*" },
    { 00440, AID_ROOT,      AID_SHELL,     0, "system/etc/init.goldfish.rc" },
    ... etc.

我试图同时使用AID_ROOT, AID_ROOT和AID_SYSTEM, AID_SYSTEM

该文件夹sample在编译时已成功创建，并且权限为：drw-rw-rw-根据文件浏览器（即使我分配了777，也没有执行权限）。

不过，当尝试创建文件时，logcat会打印：

02-27 17:33:30.097: W/System.err(1939): java.io.IOException: open failed: EACCES (Permission denied)
02-27 17:33:30.097: W/System.err(1939):     at java.io.File.createNewFile(File.java:939)
02-27 17:33:30.097: W/System.err(1939):     at com.android.incallui.InCallPresenter (...)
02-27 17:33:30.097: W/System.err(1939):     at com.android.incallui.CallList.notifyGenericListeners(CallList.java:541)
02-27 17:33:30.097: W/System.err(1939):     at com.android.incallui.CallList.onUpdate(CallList.java:188)
02-27 17:33:30.098: W/System.err(1939):     at com.android.incallui.Call.update(Call.java:311)
02-27 17:33:30.098: W/System.err(1939):     at com.android.incallui.Call.-wrap0(Call.java)
02-27 17:33:30.098: W/System.err(1939):     at com.android.incallui.Call$1.onDetailsChanged(Call.java:208)
02-27 17:33:30.098: W/System.err(1939):     at android.telecom.Call$4.run(Call.java:1156)
02-27 17:33:30.098: W/System.err(1939):     at android.os.Handler.handleCallback(Handler.java:739)
02-27 17:33:30.098: W/System.err(1939):     at android.os.Handler.dispatchMessage(Handler.java:95)
02-27 17:33:30.098: W/System.err(1939):     at android.os.Looper.loop(Looper.java:148)
02-27 17:33:30.098: W/System.err(1939):     at android.app.ActivityThread.main(ActivityThread.java:5417)
02-27 17:33:30.098: W/System.err(1939):     at java.lang.reflect.Method.invoke(Native Method)
02-27 17:33:30.098: W/System.err(1939):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
02-27 17:33:30.098: W/System.err(1939):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
02-27 17:33:30.098: W/System.err(1939): Caused by: android.system.ErrnoException: open failed: EACCES (Permission denied)
02-27 17:33:30.098: W/System.err(1939):     at libcore.io.Posix.open(Native Method)
02-27 17:33:30.098: W/System.err(1939):     at libcore.io.BlockGuardOs.open(BlockGuardOs.java:186)
02-27 17:33:30.098: W/System.err(1939):     at java.io.File.createNewFile(File.java:932)
02-27 17:33:30.098: W/System.err(1939):     ... 16 more