Messages in this thread | | | Date | Mon, 3 Feb 2014 22:31:27 +0000 | From | Al Viro <> | Subject | Re: [PATCH v2] ceph: fix posix ACL hooks |
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On Mon, Feb 03, 2014 at 01:44:22PM -0800, Linus Torvalds wrote: > On Mon, Feb 3, 2014 at 1:39 PM, Al Viro <viro@zeniv.linux.org.uk> wrote: > > > > If we really have hardlinks, the result of permission check would better > > be a function of inode itself - as in, "if it gives different results > > for two pathnames reachable for the same user, we have a bug". ^^^^^^^^^ > No. You're wrong. > > EVEN ON A UNIX FILESYSTEM THE PATH IS MEANINGFUL. > > Do this: create a hardlink in two different directories. Make the > *directory* permissions for one of the directories be something you > cannot traverse. Now try to check the permissions of the *same* inode > through those two paths. Notice how you get *different* results. > > Really.
Yes. In one case we won't get to looking at the permissions of that thing at all. > Now, imagine that you are doing the same thing over a network. On the > server, there may be a single inode for the file, but when the client > gives the server a pathname, the two pathnames to that single inode > ARE NOT EQUIVALENT.
Why do we pretend that those are links, in the first place?
> And the fact is, filesystems with hardlinks and path-name-based > operations do exist. cifs with the unix extensions is one of them.
Pox on Tridge...
I really, really hate that change; I can buy "->getxattr() has inconvenient interface because of lousy protocol design", but spreading the same to ->permission(), with everything that will fall out of that... <shudder>
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