Messages in this thread | | | Date | Mon, 3 Feb 2014 13:44:22 -0800 | Subject | Re: [PATCH v2] ceph: fix posix ACL hooks | From | Linus Torvalds <> |
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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.
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.
And the fact is, filesystems with hardlinks and path-name-based operations do exist. cifs with the unix extensions is one of them.
Al, face it, you're wrong this time.
Linus
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