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Message-ID: <20110208042708.GG1457@outflux.net> Date: Mon, 7 Feb 2011 20:27:08 -0800 From: Kees Cook <kees.cook@...onical.com> To: James Morris <jmorris@...ei.org> Cc: linux-kernel@...r.kernel.org, Al Viro <viro@....linux.org.uk> Subject: Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec On Tue, Feb 08, 2011 at 02:43:15PM +1100, James Morris wrote: > On Mon, 7 Feb 2011, Kees Cook wrote: > > Sure, I know about O_CLOEXEC, but this is about protecting the > > just-been-execed setuid process from the attacking process that has no > > reason to set O_CLOEXEC. > > > > Something like this needs to be enforced on the kernel side. I.e. these > > file in /proc need to have O_CLOEXEC set in a way that cannot be unset. > > > > > Changing the behavior in the core kernel will break userspace. > > > > I don't think /proc/$pid/* needs to stay open across execs, does it? Or at > > least the non-0444 files should be handled separately. > > Actually, this seems like a more general kind of bug in proc rather than a > leaked fd. Each child task should only see its own /proc/[pid] data. Right, that's precisely the problem. The unprivileged process can read the setuid process's /proc files. -Kees -- Kees Cook Ubuntu Security Team -- 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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