Messages in this thread | | | From | (Eric W. Biederman) | Date | Tue, 08 Feb 2011 12:17:05 -0800 | Subject | Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec |
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Kees Cook <kees.cook@canonical.com> writes:
> On Tue, Feb 08, 2011 at 02:43:15PM +1100, James Morris wrote: >> On Mon, 7 Feb 2011, Kees Cook wrote: >> > Sure, I know about O_CLOEXEC, but this is about protecting the >> > just-been-execed setuid process from the attacking process that has no >> > reason to set O_CLOEXEC. >> > >> > Something like this needs to be enforced on the kernel side. I.e. these >> > file in /proc need to have O_CLOEXEC set in a way that cannot be unset. >> > >> > > Changing the behavior in the core kernel will break userspace. >> > >> > I don't think /proc/$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.
If these are things that we actually care about we should sprinkle in a few more ptrace_may_access calls into implementations of the relevant proc files.
Eric
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