Re: [PATCH 04/24] VFS: Add LSM hooks for filesystem context [ver #7]

From: David Howells
Date: Tue Apr 24 2018 - 11:22:59 EST

Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:

> Neither fsopen() nor fscontext_fs_write() appear to perform any kind of
> up-front permission checking (DAC or MAC), although some security hooks may
> be ultimately called to allocate structures, parse security options, etc.
> Is there a reason not apply a may_mount() or similar check up front?

may_mount() is called by fsmount() at the moment. It may make sense to move
this earlier to fsopen(). Note that there's also going to be something that
looks like:

fd = fspick("/mnt");
fsmount(fd, "/a", MNT_NOEXEC); // ie. bind mount


fd = fspick("/mnt");
write(fd, "o intr");
write(fd, "x reconfigure"); // ie. something like remount

I guess we'd want to call may_mount() in fspick() too. But there's also the
possibility of using this to create a query interfact too:

fd = fspick("/mnt");
write(fd, "q intr");
read(fd, value_buffer);