Messages in this thread | | | Date | Tue, 2 Oct 2012 22:37:45 -0700 (PDT) | From | David Rientjes <> | Subject | Re: [PATCH] mm: use %pK for /proc/vmallocinfo |
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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. >
So root does echo 0 > /proc/sys/kernel/kptr_restrict first. Again: what are you trying to protect?
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