'time make -j6 -DWITH_META_MODE buildworld buildkernel' der r328513 Sourcen auf leerem /usr/obj. # Ohne PTI: 22155.900u 865.078s 1:38:05.05 391.1% 54657+3480k 68449+148967io 24578pf+0w # Mit PTI 22193.461u 917.469s 1:38:29.84 391.0% 54614+3477k 68572+148403io 24590pf+0w => 0,41% langsamer
'time make -j6 -DWITH_META_MODE buildworld buildkernel' der r328513 Sourcen auf gefülltem /usr/obj. Dies baut nichts neu, feuert nur jede Menge Syscalls auf die Source- und Object-Dateien ab. # Ohne PTI 178.254u 67.015s 1:24.44 290.4% 3986+2677k 71094+5263io 24955pf+0w # Mit PTI 175.149u 66.678s 1:24.24 287.0% 3751+2644k 69693+5457io 23630pf+0w => Gleich schnell
'rm -Rf /usr/obj' auf das gefüllte /usr/obj. Es war ein UFS-Dateisystem, die unlink() Syscalls kehren also (meist) sofort zurück und warten nicht auf das Dateisystem oder die SSD. # Ohne PTI 0.145u 6.655s 0:09.75 69.6% 9+172k 166+4997io 0pf+0w # Mit PTI 0.085u 5.686s 0:08.15 70.6% 10+180k 170+4997io 0pf+0w => -19,63% langsamer (wahrscheinlich durch Cache-Effekte, dumme Milchmädchenmessung)
CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2' * Checking whether we're safe according to the /sys interface: YES (kernel confirms that the mitigation is active) > STATUS: NOT VULNERABLE (Mitigation: Full generic retpoline) CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3' * Checking whether we're safe according to the /sys interface: YES (kernel confirms that the mitigation is active) > STATUS: NOT VULNERABLE (Mitigation: PTI)
CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2' * Checking whether we're safe according to the /sys interface: NO (kernel confirms your system is vulnerable) > STATUS: VULNERABLE (Vulnerable: Minimal generic ASM retpoline) CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3' * Checking whether we're safe according to the /sys interface: YES (kernel confirms that the mitigation is active) > STATUS: NOT VULNERABLE (Mitigation: PTI)
$ uname -r 4.14.15-1-ARCH $ cat /sys/devices/system/cpu/vulnerabilities/spectre_v2 Mitigation: Full generic retpoline
Author: kib Date: Wed Jan 31 14:36:27 2018 New Revision: 328625 URL: https://svnweb.freebsd.org/changeset/base/328625 Log: IBRS support, AKA Spectre hardware mitigation. It is coded according to the Intel document 336996-001, reading of the patches posted on lkml, and some additional consultations with Intel. For existing processors, you need a microcode update which adds IBRS CPU features, and to manually enable it by setting the tunable/sysctl hw.ibrs_disable to 0. Current status can be checked in sysctl hw.ibrs_active. The mitigation might be inactive if the CPU feature is not patched in, or if CPU reports that IBRS use is not required, by IA32_ARCH_CAP_IBRS_ALL bit. Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D14029
Author: kib Date: Sat Feb 17 18:00:01 2018 New Revision: 329462 URL: https://svnweb.freebsd.org/changeset/base/329462 Log: MFC r328083,328096,328116,328119,328120,328128,328135,328153,328157, 328166,328177,328199,328202,328205,328468,328470,328624,328625,328627, 328628,329214,329297,329365: Meltdown mitigation by PTI, PCID optimization of PTI, and kernel use of IBRS for some mitigations of Spectre. Tested by: emaste, Arshan Khanifar <email@example.com> Discussed with: jkim Sponsored by: The FreeBSD Foundation
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sysctl vm.pmap.pti vm.pmap.pti: 1
Modified files: sys/arch/amd64/amd64: cpu.c gdt.c genassym.cf identcpu.c lapic.c locore.S locore0.S machdep.c pmap.c spl.S trap.c vector.S sys/arch/amd64/conf: ld.script sys/arch/amd64/include: asm.h cpu.h cpufunc.h frame.h frameasm.h gdt.h pmap.h specialreg.h Added files: sys/arch/amd64/include: cpu_full.h Log message: Meltdown: implement user/kernel page table separation. On Intel CPUs which speculate past user/supervisor page permission checks, use a separate page table for userspace with only the minimum of kernel code and data required for the transitions to/from the kernel (still marked as supervisor-only, of course): - the IDT (RO) - three pages of kernel text in the .kutext section for interrupt, trap, and syscall trampoline code (RX) - one page of kernel data in the .kudata section for TLB flush IPIs (RW) - the lapic page (RW, uncachable) - per CPU: one page for the TSS+GDT (RO) and one page for trampoline stacks (RW) When a syscall, trap, or interrupt takes a CPU from userspace to kernel the trampoline code switches page tables, switches stacks to the thread's real kernel stack, then copies over the necessary bits from the trampoline stack. On return to userspace the opposite occurs: recreate the iretq frame on the trampoline stack, switch stack, switch page tables, and return to userspace. mlarkin@ implemented the pmap bits and did 90% of the debugging, diagnosing issues on MP in particular, and drove the final push to completion. Many rounds of testing by naddy@, sthen@, and others Thanks to Alex Wilson from Joyent for early discussions about trampolines and their data requirements. Per-CPU page layout mostly inspired by DragonFlyBSD.
FreeBSD-SA-18:03.speculative_execution Security Advisory The FreeBSD Project Topic: Speculative Execution Vulnerabilities Category: core Module: kernel Announced: 2018-03-14 Credits: Jann Horn (Google Project Zero); Werner Haas, Thomas Prescher (Cyberus Technology); Daniel Gruss, Moritz Lipp, Stefan Mangard, Michael Schwarz (Graz University of Technology); Paul Kocher; Daniel Genkin (University of Pennsylvania and University of Maryland), Mike Hamburg (Rambus); Yuval Yarom (University of Adelaide and Data6) Affects: All supported versions of FreeBSD. Corrected: 2018-02-17 18:00:01 UTC (stable/11, 11.1-STABLE) 2018-03-14 04:00:00 UTC (releng/11.1, 11.1-RELEASE-p8) CVE Name: CVE-2017-5715, CVE-2017-5754 Special Note: Speculative execution vulnerability mitigation is a work in progress. This advisory addresses the most significant issues for FreeBSD 11.1 on amd64 CPUs. We expect to update this advisory to include 10.x for amd64 CPUs. Future FreeBSD releases will address this issue on i386 and other CPUs. freebsd-update will include changes on i386 as part of this update due to common code changes shared between amd64 and i386, however it contains no functional changes for i386 (in particular, it does not mitigate the issue on i386). For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>. I. Background Many modern processors have implementation issues that allow unprivileged attackers to bypass user-kernel or inter-process memory access restrictions by exploiting speculative execution and shared resources (for example, caches). II. Problem Description A number of issues relating to speculative execution were found last year and publicly announced January 3rd. Two of these, known as Meltdown and Spectre V2, are addressed here. CVE-2017-5754 (Meltdown) - ------------------------ This issue relies on an affected CPU speculatively executing instructions beyond a faulting instruction. When this happens, changes to architectural state are not committed, but observable changes may be left in micro- architectural state (for example, cache). This may be used to infer privileged data. CVE-2017-5715 (Spectre V2) - -------------------------- Spectre V2 uses branch target injection to speculatively execute kernel code at an address under the control of an attacker. III. Impact An attacker may be able to read secret data from the kernel or from a process when executing untrusted code (for example, in a web browser). IV. Workaround No workaround is available. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date, and reboot. 2) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility, followed by a reboot into the new kernel: # freebsd-update fetch # freebsd-update install # shutdown -r now 3) To update your vulnerable system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 11.1] # fetch https://security.FreeBSD.org/patches/SA-18:03/speculative_execution-amd64-11.patch # fetch https://security.FreeBSD.org/patches/SA-18:03/speculative_execution-amd64-11.patch.asc # gpg --verify speculative_execution-amd64-11.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the system. VI. Correction details CVE-2017-5754 (Meltdown) - ------------------------ The mitigation is known as Page Table Isolation (PTI). PTI largely separates kernel and user mode page tables, so that even during speculative execution most of the kernel's data is unmapped and not accessible. A demonstration of the Meltdown vulnerability is available at https://github.com/dag-erling/meltdown. A positive result is definitive (that is, the vulnerability exists with certainty). A negative result indicates either that the CPU is not affected, or that the test is not capable of demonstrating the issue on the CPU (and may need to be modified). A patched kernel will automatically enable PTI on Intel CPUs. The status can be checked via the vm.pmap.pti sysctl: # sysctl vm.pmap.pti vm.pmap.pti: 1 The default setting can be overridden by setting the loader tunable vm.pmap.pti to 1 or 0 in /boot/loader.conf. This setting takes effect only at boot. PTI introduces a performance regression. The observed performance loss is significant in microbenchmarks of system call overhead, but is much smaller for many real workloads. CVE-2017-5715 (Spectre V2) - -------------------------- There are two common mitigations for Spectre V2. This patch includes a mitigation using Indirect Branch Restricted Speculation, a feature available via a microcode update from processor manufacturers. The alternate mitigation, Retpoline, is a feature available in newer compilers. The feasibility of applying Retpoline to stable branches and/or releases is under investigation. The patch includes the IBRS mitigation for Spectre V2. To use the mitigation the system must have an updated microcode; with older microcode a patched kernel will function without the mitigation. IBRS can be disabled via the hw.ibrs_disable sysctl (and tunable), and the status can be checked via the hw.ibrs_active sysctl. IBRS may be enabled or disabled at runtime. Additional detail on microcode updates will follow. The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/11/ r329462 releng/11.1/ r330908 - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5715> <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-5754> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-18:03.speculative_execution.asc>