Re: PROBLEM: fanotify_mark EFAULT on x86

[Matthew Wilcox]

On Sun, Nov 01, 2020 at 10:27:38PM +0100, Paweł Jasiak wrote:
> I am trying to run examples from man fanotify.7 but fanotify_mark always
> fail with errno = EFAULT.
> 
> fanotify_mark declaration is
> 
> SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
> 			      __u64, mask, int, dfd,
> 			      const char  __user *, pathname)

Don't worry about that.  You aren't calling the SYSCALL, you're calling
glibc and glibc is turning it into a syscall.

extern int fanotify_mark (int __fanotify_fd, unsigned int __flags,
                          uint64_t __mask, int __dfd, const char *__pathname)

> When 
> 
> fanotify_mark(4, FAN_MARK_ADD | FAN_MARK_ONLYDIR,
>               FAN_CREATE | FAN_ONDIR, AT_FDCWD, 0xdeadc0de)

The last argument is supposed to be a pointer to a string.  I'm guessing
there's no string at 0xdeadc0de.