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Date: Tue, 2 Oct 2012 22:15:14 -0700 From: Kees Cook <keescook@...omium.org> To: David Rientjes <rientjes@...gle.com> Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Minchan Kim <minchan@...nel.org>, Joe Perches <joe@...ches.com>, Kautuk Consul <consul.kautuk@...il.com>, linux-mm@...ck.org, Brad Spengler <spender@...ecurity.net> Subject: Re: [PATCH] mm: use %pK for /proc/vmallocinfo On Tue, Oct 2, 2012 at 10:12 PM, David Rientjes <rientjes@...gle.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@...ecurity.net> >> Signed-off-by: Kees Cook <keescook@...omium.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 -- 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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