如何确定是否启用了CONFIG_FANOTIFY_ACCESS_PERMISSIONS? [英] How to find out whether CONFIG_FANOTIFY_ACCESS_PERMISSIONS is enabled?

问题描述

我想使用 fanotify(7) ，我遇到的问题是，尽管配置了 CONFIG_FANOTIFY ，但在某些内核上， CONFIG_FANOTIFY_ACCESS_PERMISSIONS 无法正常工作.

至少我想报告这种情况.

现在在Debian和Ubuntu上，我可以使用等效于 grep CONFIG_FANOTIFY_ACCESS_PERMISSIONS/boot/config-$(uname -r)的功能来验证该功能是否可用.在其他一些系统上，我可以使用等效于 zgrep CONFIG_FANOTIFY_ACCESS_PERMISSIONS/proc/config.gz 的系统，但是这两个方法可能没有涵盖其他系统.

是否有一种方法可以在任何 fanotify(7)函数中弄清楚当前运行的内核上是否可以使用fanotify权限处理?

当未实现 fanotify_mark()时，我在想一种类似于返回的 ENOSYS 的方法(解决方案

当通过 FAN_ALL_PERM_EVENTS 时，似乎 fanotify_mark()返回 EINVAL 但是 CONFIG_FANOTIFY_ACCESS_PERMISSIONS 已禁用.

请参见 fs/notify/fanotify/fanotify_user.c 在内核源代码中:

  SYSCALL_DEFINE5(fanotify_mark，int，fanotify_fd，unsigned int，标志，__u64，mask，int，dfd，const char __user *，路径名){...#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS如果(遮罩&〜(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))#别的如果(遮罩&〜(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))#万一返回-EINVAL; 

I want to make use of fanotify(7) and the problem I run into is that on some kernels CONFIG_FANOTIFY_ACCESS_PERMISSIONS does not work, although CONFIG_FANOTIFY is configured.

At the very least I'd like to report this condition.

Now on Debian and Ubuntu I could use the equivalent of grep CONFIG_FANOTIFY_ACCESS_PERMISSIONS /boot/config-$(uname -r) to verify that the feature is available. On some other systems I could use the equivalent of zgrep CONFIG_FANOTIFY_ACCESS_PERMISSIONS /proc/config.gz, but there are probably some more systems that are not covered by these two methods.

Is there a way to figure out in any of the fanotify(7) functions whether or not fanotify permission handling is available on the kernel currently running?

I was thinking of a method similar to the returned ENOSYS when fanotify_mark() is not implemented (fanotify_mark(2)), but could not find anything like that in the documentation.

解决方案

It seems that fanotify_mark() returns EINVAL when FAN_ALL_PERM_EVENTS is passed but CONFIG_FANOTIFY_ACCESS_PERMISSIONS is disabled.

See fs/notify/fanotify/fanotify_user.c in kernel sources:

SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
                              __u64, mask, int, dfd,
                              const char  __user *, pathname)
{
...

#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
        if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
#else
        if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
#endif
                return -EINVAL;

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