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Message-ID: <20091025093604.GA1501@ucw.cz> Date: Sun, 25 Oct 2009 10:36:04 +0100 From: Pavel Machek <pavel@....cz> To: Trond Myklebust <trond.myklebust@....uio.no> Cc: Jan Kara <jack@...e.cz>, "J. Bruce Fields" <bfields@...ldses.org>, "Serge E. Hallyn" <serue@...ibm.com>, kernel list <linux-kernel@...r.kernel.org>, linux-fsdevel@...r.kernel.org, viro@...iv.linux.org.uk, jamie@...reable.org Subject: Re: symlinks with permissions On Mon 2009-10-26 13:57:49, Trond Myklebust wrote: > On Mon, 2009-10-26 at 18:46 +0100, Jan Kara wrote: > > That's what I'd think as well but it does not as I've just learned and > > tested :) proc_pid_follow_link actually directly gives a dentry of the > > target file without checking permissions on the way. It is weider. That symlink even has permissions. Those are not checked, either. > I seem to remember that is deliberate, the point being that a symlink > in /proc/*/fd/ may contain a path that refers to a private namespace. Well, it is unexpected and mild security hole. Part of the problem is that even if you have read-only filedescriptor, you can upgrade it to read-write, even if path is inaccessible to you. So if someone passes you read-only filedescriptor, you can still write to it. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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