Re: [PATCH 29/38] vfs: syscall: Add fsconfig() for configuring and managing a context [ver #10]

[David Howells]

Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:

> > [*] Not without a 6-arg syscall or some other way of passing it.
> 
> Are there still architectures that have problems with 6-arg syscalls?

As I understand it, 6-arg syscalls are frowned upon.

> I suppose that, as long as there is never a case where fsconfig_set_path and
> fsconfig_set_fd both succeed, then it's not a big deal.

fsconfig_set_path/path_empty requires the 'value' argument to point to a
string, possibly "", and fsconfig_set_fd requires it to be NULL.

I can't stop you from doing:

	fd = open("/some/path", O_PATH);
	fsconfig(fsfd, fsconfig_set_fd, "fd", NULL, fd);

or:

	fd = open("/dev/sda6", O_RDWR);
	fsconfig(fsfd, fsconfig_set_path_empty, "foo", "", fd);

The first should fail because I'm using fget() not fget_raw() and the
second will pass the string and fd number to the filesystem, which will
presumably then call fs_lookup_param() to invoke pathwalk upon it - which will
likely also fail.

David