From mboxrd@z Thu Jan 1 00:00:00 1970 From: keescook@chromium.org (Kees Cook) Date: Thu, 7 Jul 2016 13:19:26 -0400 Subject: [PATCH 4/9] arm64/uaccess: Enable hardened usercopy In-Reply-To: <20160707100717.GB8306@leverpostej> References: <1467843928-29351-1-git-send-email-keescook@chromium.org> <1467843928-29351-5-git-send-email-keescook@chromium.org> <20160707100717.GB8306@leverpostej> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jul 7, 2016 at 6:07 AM, Mark Rutland wrote: > Hi, > > On Wed, Jul 06, 2016 at 03:25:23PM -0700, Kees Cook wrote: >> Enables CONFIG_HARDENED_USERCOPY checks on arm64. As done by KASAN in -next, >> renames the low-level functions to __arch_copy_*_user() so a static inline >> can do additional work before the copy. > > The checks themselves look fine, but as with the KASAN checks, it seems > a shame that this logic is duplicated per arch, integrated in subtly > different ways. > > Can we not __arch prefix all the arch uaccess helpers, and place > kasan_check_*() and check_object_size() calls in generic wrappers? > > If we're going to update all the arch uaccess helpers anyway, doing that > would make it easier to fix things up, or to add new checks in future. Yeah, I totally agree, and my work on the next step of this hardening will require something like this to separate the "check" logic from the "copy" logic, as I want to introduce a set of constant-sized copy_*_user helpers. Though currently x86 poses a weird problem in this regard (they have separate code paths for copy_* and __copy*, but I think it's actually a harmless(?) mistake. For now, I'd like to leave this as-is, and then do the copy_* cleanup, then do step 2 (slab whitelisting). -Kees -- Kees Cook Chrome OS & Brillo Security