Messages in this thread | | | Date | Mon, 8 Mar 2010 17:49:10 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: Upstream first policy |
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On Tue, 9 Mar 2010, Al Viro wrote: > > BTW, if you actually look at apparmor (I'd suggest tomoyo, but I'm not _that_ > sadistic), you'll see how seriously do they take pathname-based *anything*. > LSM hooks for namespace operations (you know, mount, umount) are lousy, but > they exist. Not used by apparmor.
That's a good point, btw, and shows one conceptual difference between content-based and pathname-based rules.
For example, if you want to log any changes to "/etc/passwd" (which is something pretty reasonable to do at least conceptually), what about doing a bind mount on top of that file?
That bind mount doesn't actually change the underlying file in any way. It doesn't even really _access_ it. From a content standpoint of the filesystem that contains the file, it's a total no-op.
But from an attack standpoint, you don't actually care, because nobody cares about the inode that used to be the contents of "/etc/passwd": all anybody _really_ cares about is "could somebody change what happens to the _name_ '/etc/passwd'".
But yeah, it's easy to overlook namespace changes when the obvious operations are read/write/unlink/rename. And I'm not at all surprised that people do.
Linus
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