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SubjectRe: [PATCH v2] kptr_restrict for hiding kernel pointers from unprivileged users
On Fri, Dec 10, 2010 at 07:05:24PM -0500, Dan Rosenberg wrote:
> The below patch adds the %pK format specifier, the
> CONFIG_SECURITY_KPTR_RESTRICT configuration option, and the
> kptr_restrict sysctl.
>
> The %pK format specifier is designed to hide exposed kernel pointers
> from unprivileged users, specifically via /proc interfaces. Its
> behavior depends on the kptr_restrict sysctl, whose default value
> depends on CONFIG_SECURITY_KPTR_RESTRICT. If kptr_restrict is set to 0,
> no deviation from the standard %p behavior occurs. If kptr_restrict is
> set to 1, if the current user (intended to be a reader via seq_printf(),
> etc.) does not have CAP_SYSLOG (which is currently in the LSM tree),
> kernel pointers using %pK are printed as 0's. This was chosen over the
> default "(null)", which cannot be parsed by userland %p, which expects
> "(nil)".
>
> v2 improves checking for inappropriate context, on suggestion by Peter
> Zijlstra. Thanks to Thomas Graf for suggesting use of a centralized
> format specifier.
>
> Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>

This will come in very handy! Thanks for working on this approach. :)

Acked-by: Kees Cook <kees.cook@canonical.com>

-Kees

--
Kees Cook
Ubuntu Security Team


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