Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162940AbbKFVTu (ORCPT ); Fri, 6 Nov 2015 16:19:50 -0500 Received: from mail-io0-f177.google.com ([209.85.223.177]:34725 "EHLO mail-io0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1162346AbbKFVTr (ORCPT ); Fri, 6 Nov 2015 16:19:47 -0500 MIME-Version: 1.0 In-Reply-To: <7h8u6ahm7d.fsf@deeprootsystems.com> References: <1446685239-28522-1-git-send-email-labbott@fedoraproject.org> <20151105094615.GP8644@n2100.arm.linux.org.uk> <563B81DA.2080409@redhat.com> <20151105162719.GQ8644@n2100.arm.linux.org.uk> <563BFCC4.8050705@redhat.com> <563CF510.9080506@redhat.com> <7h8u6ahm7d.fsf@deeprootsystems.com> Date: Fri, 6 Nov 2015 13:19:46 -0800 X-Google-Sender-Auth: mzKM9tfb4_fKXsKQVGihCnLZdp4 Message-ID: Subject: Re: [PATCH] arm: Use kernel mm when updating section permissions From: Kees Cook To: Kevin Hilman Cc: info@kernelci.org, Russell King - ARM Linux , Laura Abbott , Catalin Marinas , Will Deacon , "linux-arm-kernel@lists.infradead.org" , LKML , Linux-MM , Laura Abbott , Shuah Khan , Tyler Baker Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3731 Lines: 109 On Fri, Nov 6, 2015 at 1:06 PM, Kevin Hilman wrote: > Kees Cook writes: > >> On Fri, Nov 6, 2015 at 12:11 PM, Kevin Hilman wrote: >>> On Fri, Nov 6, 2015 at 11:12 AM, Kees Cook wrote: >>> >>> [...] >>> >>>> Hi Kevin and Kernel CI folks, >>>> >>>> Could lkdtm get added to the kernel-CI workflows? Extracting and >>>> validating Oops details when poking lkdtm would be extremely valuable >>>> for these cases. :) >>> >>> Yeah, we can add that. >>> >>> What arches should we expect this to be working on? For starters >> >> This is a great question. ;) They're a mix of CONFIG and hardware >> feature specific, so probably they should be run on all architectures >> and we can figure out what's missing in each case. >> >> Everything built with CONFIG_DEBUG_RODATA should pass these: >> >> WRITE_RO >> WRITE_KERN >> EXEC_DATA >> EXEC_STACK >> EXEC_KMALLOC >> EXEC_VMALLOC >> >> But architectures without CONFIG_DEBUG_RODATA should be shamed. ;) >> >> Passing EXEC_USERSPACE requires SMEP on x86, and PXN on arm64. >> Passing ACCESS_USERSPACE rquires SMAP on x86, and PAN on arm64. >> >> The recent PAN emulation CONFIG_CPU_SW_DOMAIN_PAN on non-LPAE arm >> should cover ACCESS_USERSPACE too, and maybe EXEC_USERSPACE, but I >> haven't taken a close look. > > A quick test on arm32 and both ACCESS_ and EXEC_USERSPACE tests pass > (meaning they trigger the WARNs). I'd expect a full Oops, not a WARN, but maybe CONFIG_CPU_SW_DOMAIN_PAN needs to use a bigger hammer. Russell, what sort of trap is DOMAIN_PAN expected to be triggering? >> It might be useful, frankly, to test everything in lkdtm. > > So I gave this a quick spin on an ARM board (qcom-apq8064-ifc6410) > using a dumb script[1] (for now avoiding the tests that cause a lockup > so I can test multiple features without a reboot.) Seems like most of > them are producing a failure. > > However, this got me to thinking that one should probably write a > kselftest for this feature, and catch quite a few issues with the ones > that don't cause a hard lockup. One would just need to be a bit smarter > than my script and do something to trap SIG* (or the parent catching > SIGCHLD) in order to be able to help determine failure, then grab the > dmesg and log it. > > Having these test integrated into kselftest, and maintained along with > the the kernel features would be *way* better than trying to maintain a > set of tests in kernel CI for this feature, since right now we're > working just building/running all the selftests automatically. > > What do you think about coming up with a kselftest for this stuff? At > least the non-lockup stuff? Well, all the stuff I wrote tests for in lkdtm expect the kernel to entirely Oops, and examining the Oops from outside is needed to verify it was the correct type of Oops. I don't think testing via lkdtm can be done from kselftest sensibly. -Kees > > I'm not volunteering to write up the kselftest, but I will guarantee > that it get run on a broad range of boards once it exists. :) > > Kevin > > [1] > #!/bin/sh > > crash_test_dummy() { > echo $1> /sys/kernel/debug/provoke-crash/DIRECT > } > > # Find all the tests that don't lockup > TESTS=$(cat /sys/kernel/debug/provoke-crash/DIRECT |grep -v types| grep -v LOCK |grep -v PANIC) > > for test in $TESTS; do > echo "Performing test: $test" > crash_test_dummy $test & > sleep 1 > done -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/