Messages in this thread | | | Date | Tue, 2 Oct 2012 22:15:14 -0700 | Subject | Re: [PATCH] mm: use %pK for /proc/vmallocinfo | From | Kees Cook <> |
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On Tue, Oct 2, 2012 at 10:12 PM, David Rientjes <rientjes@google.com> wrote: > On Tue, 2 Oct 2012, Kees Cook wrote: > >> In the paranoid case of sysctl kernel.kptr_restrict=2, mask the kernel >> virtual addresses in /proc/vmallocinfo too. >> >> Reported-by: Brad Spengler <spender@grsecurity.net> >> Signed-off-by: Kees Cook <keescook@chromium.org> > > /proc/vmallocinfo is S_IRUSR, not S_IRUGO, so exactly what are you trying > to protect?
Trying to block the root user from seeing virtual memory addresses (mode 2 of kptr_restrict).
Documentation/sysctl/kernel.txt: "This toggle indicates whether restrictions are placed on exposing kernel addresses via /proc and other interfaces. When kptr_restrict is set to (0), there are no restrictions. When kptr_restrict is set to (1), the default, kernel pointers printed using the %pK format specifier will be replaced with 0's unless the user has CAP_SYSLOG. When kptr_restrict is set to (2), kernel pointers printed using %pK will be replaced with 0's regardless of privileges."
Even though it's S_IRUSR, it still needs %pK for the paranoid case.
-Kees
-- Kees Cook Chrome OS Security
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