* [PATCH] security/Kconfig: further restrict HARDENED_USERCOPY @ 2017-03-09 17:29 ` Tycho Andersen 0 siblings, 0 replies; 4+ messages in thread From: Tycho Andersen @ 2017-03-09 17:29 UTC (permalink / raw) To: linux-security-module 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. v2: add !MMU depend as well Signed-off-by: Tycho Andersen <tycho@docker.com> CC: Kees Cook <keescook@chromium.org> CC: "Serge E. Hallyn" <serge@hallyn.com> CC: James Morris <james.l.morris@oracle.com> --- security/Kconfig | 2 ++ 1 file changed, 2 insertions(+) diff --git a/security/Kconfig b/security/Kconfig index 3ff1bf9..aeabd40 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 !ARCH_HAS_DEVMEM_IS_ALLOWED || STRICT_DEVMEM || !MMU select BUG help This option checks for obviously wrong memory regions when -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] security/Kconfig: further restrict HARDENED_USERCOPY @ 2017-03-09 17:29 ` Tycho Andersen 0 siblings, 0 replies; 4+ messages in thread From: Tycho Andersen @ 2017-03-09 17:29 UTC (permalink / raw) To: Kees Cook, James Morris Cc: linux-security-module, linux-kernel, Tycho Andersen, Serge E. Hallyn 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. v2: add !MMU depend as well Signed-off-by: Tycho Andersen <tycho@docker.com> CC: Kees Cook <keescook@chromium.org> CC: "Serge E. Hallyn" <serge@hallyn.com> CC: James Morris <james.l.morris@oracle.com> --- security/Kconfig | 2 ++ 1 file changed, 2 insertions(+) diff --git a/security/Kconfig b/security/Kconfig index 3ff1bf9..aeabd40 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 !ARCH_HAS_DEVMEM_IS_ALLOWED || STRICT_DEVMEM || !MMU select BUG help This option checks for obviously wrong memory regions when -- 2.7.4 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH] security/Kconfig: further restrict HARDENED_USERCOPY 2017-03-09 17:29 ` Tycho Andersen @ 2017-03-09 19:18 ` Kees Cook -1 siblings, 0 replies; 4+ messages in thread From: Kees Cook @ 2017-03-09 19:18 UTC (permalink / raw) To: linux-security-module On Thu, Mar 9, 2017 at 9:29 AM, Tycho Andersen <tycho@docker.com> wrote: > 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. > > v2: add !MMU depend as well Sorry I keep revising my thoughts on this... so, the bad combos, IMO, are /dev/kmem or /dev/mem. kmem is easy: we unconditionally require !DEVKMEM. The /dev/mem one continues to hurt my head, but here's my current thinking (which, if it seems correct should likely be reflected in the commit message): The following cases for /dev/mem should be safe: - /dev/mem entirely disabled (!DEVMEM) - /dev/mem with strict checking (STRICT_DEVMEM) Everything else is not okay, i.e. if an architecture lacks ARCH_HAS_DEVMEM_IS_ALLOWED, we must reject DEVMEM entirely since it cannot select STRICT_DEVMEM. So, sorry for the confusion, but I think this is the correct combo: depends on !DEVKMEM depends on !DEVMEM || STRICT_DEVMEM That should cover it, unless I'm still thinking sideways. -Kees > > Signed-off-by: Tycho Andersen <tycho@docker.com> > CC: Kees Cook <keescook@chromium.org> > CC: "Serge E. Hallyn" <serge@hallyn.com> > CC: James Morris <james.l.morris@oracle.com> > --- > security/Kconfig | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/security/Kconfig b/security/Kconfig > index 3ff1bf9..aeabd40 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 !ARCH_HAS_DEVMEM_IS_ALLOWED || STRICT_DEVMEM || !MMU > select BUG > help > This option checks for obviously wrong memory regions when > -- > 2.7.4 > -- Kees Cook Pixel Security -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] security/Kconfig: further restrict HARDENED_USERCOPY @ 2017-03-09 19:18 ` Kees Cook 0 siblings, 0 replies; 4+ messages in thread From: Kees Cook @ 2017-03-09 19:18 UTC (permalink / raw) To: Tycho Andersen; +Cc: James Morris, linux-security-module, LKML, Serge E. Hallyn On Thu, Mar 9, 2017 at 9:29 AM, Tycho Andersen <tycho@docker.com> wrote: > 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. > > v2: add !MMU depend as well Sorry I keep revising my thoughts on this... so, the bad combos, IMO, are /dev/kmem or /dev/mem. kmem is easy: we unconditionally require !DEVKMEM. The /dev/mem one continues to hurt my head, but here's my current thinking (which, if it seems correct should likely be reflected in the commit message): The following cases for /dev/mem should be safe: - /dev/mem entirely disabled (!DEVMEM) - /dev/mem with strict checking (STRICT_DEVMEM) Everything else is not okay, i.e. if an architecture lacks ARCH_HAS_DEVMEM_IS_ALLOWED, we must reject DEVMEM entirely since it cannot select STRICT_DEVMEM. So, sorry for the confusion, but I think this is the correct combo: depends on !DEVKMEM depends on !DEVMEM || STRICT_DEVMEM That should cover it, unless I'm still thinking sideways. -Kees > > Signed-off-by: Tycho Andersen <tycho@docker.com> > CC: Kees Cook <keescook@chromium.org> > CC: "Serge E. Hallyn" <serge@hallyn.com> > CC: James Morris <james.l.morris@oracle.com> > --- > security/Kconfig | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/security/Kconfig b/security/Kconfig > index 3ff1bf9..aeabd40 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 !ARCH_HAS_DEVMEM_IS_ALLOWED || STRICT_DEVMEM || !MMU > select BUG > help > This option checks for obviously wrong memory regions when > -- > 2.7.4 > -- Kees Cook Pixel Security ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-03-09 19:18 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2017-03-09 17:29 [PATCH] security/Kconfig: further restrict HARDENED_USERCOPY Tycho Andersen 2017-03-09 17:29 ` Tycho Andersen 2017-03-09 19:18 ` Kees Cook 2017-03-09 19:18 ` Kees Cook
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