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Re: Re: /proc filesystem allows bypassing directory permissions on Linux
From: nomail () nomail com
Date: Mon, 26 Oct 2009 09:14:30 -0600

I do not think mounting /proc should change access control semantics.

It didn't in fact change anything. If the guest created hardlink to that file in a unrestricted location, what would 
you say?

Do your homework and test it. You can't create the hardlink - the link(oldpath, newpath) call will fail with EACCES if 
search permission is denied for any directory in oldpath or newpath. Documented in the manpage, and I just tested and 
verified it.

Fact is, directory permissions are relevant in Unix. Despite it's permissions, under the Unix access permission 
semantics the file is unwriteable for anyone but the owner, and this bug pokes a hole into that.


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