[PATCH v3] security/Kconfig: further restrict HARDENED_USERCOPY

[Tycho Andersen]

It doesn't make sense to have HARDENED_USERCOPY when either /dev/kmem is
enabled or /dev/mem can be used to read kernel memory (i.e.
!STRICT_DEVMEM).

v2: add !MMU depend as well
v3: drop !MMU, s/ARCH_HAS_DEVMEM_IS_ALLOWED/DEVMEM, which makes the above
    commit message actually match the logic again

Signed-off-by: Tycho Andersen <tycho at docker.com>
CC: Kees Cook <keescook at chromium.org>
CC: "Serge E. Hallyn" <serge at hallyn.com>
CC: James Morris <james.l.morris at oracle.com>
---
 security/Kconfig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/Kconfig b/security/Kconfig
index 3ff1bf9..4619cee 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -142,6 +142,8 @@ config HARDENED_USERCOPY
 	bool "Harden memory copies between kernel and userspace"
 	depends on HAVE_ARCH_HARDENED_USERCOPY
 	depends on HAVE_HARDENED_USERCOPY_ALLOCATOR
+	depends on !DEVKMEM
+	depends on !DEVMEM || STRICT_DEVMEM
 	select BUG
 	help
 	  This option checks for obviously wrong memory regions when
-- 
2.7.4

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