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Date: Thu, 29 Oct 2009 21:35:00 +0100 From: Pavel Machek <pavel@....cz> To: Casey Schaufler <casey@...aufler-ca.com> Cc: kernel list <linux-kernel@...r.kernel.org> Subject: Re: symlinks with permissions (fwd) Hi! > >> Do you know of any cases where this difference matters in practice? > >> > > > > Actually yes, see the bugtraq post. guest was able to write to my file > > when I expected that file to be protected. > > > > According to the bugtraq discussion, people expect directory > > permissions to work. > > Gawd, I hate to say this, but people have been improperly educated > if they expect directory permissions to behave thusly. You can not > count on the permissions on a directory to protect access on a file > that the directory contains a reference to. Hard links. Mount points. > /proc/8675309/fd. Passing file descriptors over sockets. Fork, for > heaven's sake. That's not how Linux directories really work. Actually it was how Unix directories really worked, before Linux /proc came around and broke it. See the bugtraq; yes, hardlinks are similar, but at least you see them on ls -l. Mount points are root-only. And you can't use fork to upgrade "read-only" filedescriptor to read write. 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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