“权限被拒绝"；尽管具有所有必需的文件系统权限，仍然发生错误 [英] "permission denied" error despite having all needed file system permissions

问题描述

我在android上，使用adb shell来解决我的应用程序与文件系统有关的问题.使用tinyalsa时遇到权限错误，因此我希望调查所涉及的目录.

I'm on an android, using adb shell to troubleshoot an issue which my app has with the file system. I'm encountering a permissions error when using tinyalsa, so I wish to investigate the directories involved.

cannot open device '/dev/snd/pcmC1D0c': Permission denied

如果我先su然后再stat路径中的每个项目，则外壳程序会告诉我以下权限:

If I su and then stat each item in the path, the shell tells me the following permissions:

/         (755/drwxr-xr-x)
/dev/     (755/drwxr-xr-x)
/dev/snd/ (755/drwxr-xr-x)

但是，如果我尝试在没有su的情况下尝试stat /dev/snd，则会得到Permission denied.

If I try to stat /dev/snd without su, however, I get Permission denied.

为什么会这样?我什至尝试过su -c 'chmod -R a+rx /dev/snd'，但这没什么区别.

Why would this be? I've even tried su -c 'chmod -R a+rx /dev/snd', but that makes no difference.

推荐答案

我在这方面了解不多，但是看来SELinux正在干扰.如果禁用它:

I don't know much in this area, but it appears that SELinux is interfering. If you disable it:

# In a "su" adb shell
printf 0 > /sys/fs/selinux/enforce

...您可以体验以root用户身份运行stat时看到的权限.

...you can experience the permissions that you see when you run stat as root.

这可能不是最佳解决方案，但是它将允许您执行所需的操作.如果您只针对非常专有的用户群进行开发，我建议您阅读SELinux.

This may not be the optimal solution, but it will allow you to perform the actions needed. I recommend reading up on SELinux if you are developing for anything but a very exclusive user base.

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