ACK/cmnt: [SRU artful/linux] switch Spectre V2 mitigation to retpoline

Mon Feb 5 15:14:32 UTC 2018

On 02/05/18 10:39, Andy Whitcroft wrote:
> Now that retpoline has made it to stable it is appropriate we switch
> over to this for mitigation of Spectre V2.  This form is meant to have a
> significantly lower performance penalty, and also does not require
> microcode support from the processor.
> 
> This is a large patchset as it has to revert the existing mitigations for
> Spectre V1 and V2 as these are intertwined.  We take advantage of this
> to reapply a slightly updated Spectre V1 mitigation and to more clearly
> identify those patches for when they are themselves replaced by final
> upstream versions.  Finally testing of this set threw up a procfs bug
> (LP: #1747263) which though not actuall a regression I am including as
> it breaks ADT testing.
> 
> The patches are split into 4 sections, each set has been marked up such
> that they fall out separatly in the Ubuntu change (which is included in
> the pull request at the end of this email).
> 
>   * CVE-2017-5715 (revert embargoed) // CVE-2017-5753 (revert embargoed)
>   * CVE-2017-5715 (Spectre v2 retpoline)
>   * CVE-2017-5753 (Spectre v1 Intel)
>   * [artful] panic in update_stack_state when reading /proc/<pid>/stack on i386
> 
> Full pull-request is below.  Proposing for SRU to artful/linux.
> 
> -apw
> 
> The following changes since commit b9f7706e18abb6276a87776e15596fa898cbafa4:
> 
>   x86/mm: Fix overlap of i386 CPU_ENTRY_AREA with FIX_BTMAP (2018-02-02 17:14:07 +0100)
> 
> are available in the Git repository at:
> 
>   https://git.launchpad.net/~apw/ubuntu/+source/linux/+git/pti pti/artful-retpoline-intelv1--pull
> 
> for you to fetch changes up to c50da22ff258fea6938eda9b3fc0475288b3ee7d:
> 
>   x86/unwind: Fix dereference of untrusted pointer (2018-02-04 14:47:15 +0000)

There's a remaining fixup commit
(3918407522d27d0394f9376e37615f5477997bd1 - fix! x86/retpoline/hyperv:
Convert assembler indirect jumps) which can be fixed when applying.

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> 
> ----------------------------------------------------------------
> 
>   * [artful] panic in update_stack_state when reading /proc/<pid>/stack on i386
>     (LP: #1747263)
>     - x86/unwind: Fix dereference of untrusted pointer
> 
>   * CVE-2017-5753 (Spectre v1 Intel)
>     - x86/cpu/AMD: Remove now unused definition of MFENCE_RDTSC feature
>     - SAUCE: reinstate MFENCE_RDTSC feature definition
>     - locking/barriers: introduce new observable speculation barrier
>     - bpf: prevent speculative execution in eBPF interpreter
>     - x86, bpf, jit: prevent speculative execution when JIT is enabled
>     - SAUCE: FIX: x86, bpf, jit: prevent speculative execution when JIT is enabled
>     - uvcvideo: prevent speculative execution
>     - carl9170: prevent speculative execution
>     - p54: prevent speculative execution
>     - qla2xxx: prevent speculative execution
>     - cw1200: prevent speculative execution
>     - Thermal/int340x: prevent speculative execution
>     - ipv4: prevent speculative execution
>     - ipv6: prevent speculative execution
>     - fs: prevent speculative execution
>     - net: mpls: prevent speculative execution
>     - udf: prevent speculative execution
>     - userns: prevent speculative execution
>     - powerpc: add osb barrier
>     - s390/spinlock: add osb memory barrier
>     - SAUCE: claim mitigation via observable speculation barrier
> 
>   * CVE-2017-5715 (Spectre v2 retpoline)
>     - x86/asm: Fix inline asm call constraints for Clang
>     - kvm: vmx: Scrub hardware GPRs at VM-exit
>     - sysfs/cpu: Add vulnerability folder
>     - x86/cpu: Implement CPU vulnerabilites sysfs functions
>     - x86/tboot: Unbreak tboot with PTI enabled
>     - objtool: Detect jumps to retpoline thunks
>     - objtool: Allow alternatives to be ignored
>     - x86/retpoline: Add initial retpoline support
>     - x86/spectre: Add boot time option to select Spectre v2 mitigation
>     - x86/retpoline/crypto: Convert crypto assembler indirect jumps
>     - x86/retpoline/entry: Convert entry assembler indirect jumps
>     - x86/retpoline/ftrace: Convert ftrace assembler indirect jumps
>     - x86/retpoline/hyperv: Convert assembler indirect jumps
>     - fix! x86/retpoline/hyperv: Convert assembler indirect jumps
>     - x86/retpoline/xen: Convert Xen hypercall indirect jumps
>     - x86/retpoline/checksum32: Convert assembler indirect jumps
>     - x86/retpoline/irq32: Convert assembler indirect jumps
>     - x86/retpoline: Fill return stack buffer on vmexit
>     - selftests/x86: Add test_vsyscall
>     - x86/pti: Fix !PCID and sanitize defines
>     - security/Kconfig: Correct the Documentation reference for PTI
>     - x86,perf: Disable intel_bts when PTI
>     - x86/retpoline: Remove compile time warning
>     - [Config] enable CONFIG_GENERIC_CPU_VULNERABILITIES
>     - [Config] enable CONFIG_RETPOLINE
>     - [Packaging] retpoline -- add call site validation
>     - [Config] disable retpoline checks for first upload
> 
>   * CVE-2017-5715 (revert embargoed) // CVE-2017-5753 (revert embargoed)
>     - Revert "UBUNTU: SAUCE: x86/entry: Fix up retpoline assembler labels"
>     - Revert "kvm: vmx: Scrub hardware GPRs at VM-exit"
>     - Revert "Revert "x86/svm: Add code to clear registers on VM exit""
>     - Revert "UBUNTU: SAUCE: x86/microcode: Extend post microcode reload to
>       support IBPB feature -- repair missmerge"
>     - Revert "UBUNTU: SAUCE: x86/kvm: Fix stuff_RSB() for 32-bit"
>     - Revert "s390/spinlock: add gmb memory barrier"
>     - Revert "powerpc: add gmb barrier"
>     - Revert "x86/cpu/AMD: Remove now unused definition of MFENCE_RDTSC feature"
>     - Revert "x86/svm: Add code to clear registers on VM exit"
>     - Revert "x86/svm: Add code to clobber the RSB on VM exit"
>     - Revert "KVM: x86: Add speculative control CPUID support for guests"
>     - Revert "x86/svm: Set IBPB when running a different VCPU"
>     - Revert "x86/svm: Set IBRS value on VM entry and exit"
>     - Revert "KVM: SVM: Do not intercept new speculative control MSRs"
>     - Revert "x86/microcode: Extend post microcode reload to support IBPB feature"
>     - Revert "x86/cpu/AMD: Add speculative control support for AMD"
>     - Revert "x86/entry: Use retpoline for syscall's indirect calls"
>     - Revert "x86/syscall: Clear unused extra registers on 32-bit compatible
>       syscall entrance"
>     - Revert "x86/syscall: Clear unused extra registers on syscall entrance"
>     - Revert "x86/spec_ctrl: Add lock to serialize changes to ibrs and ibpb
>       control"
>     - Revert "x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature"
>     - Revert "x86/kvm: Pad RSB on VM transition"
>     - Revert "x86/kvm: Toggle IBRS on VM entry and exit"
>     - Revert "x86/kvm: Set IBPB when switching VM"
>     - Revert "x86/kvm: add MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD to kvm"
>     - Revert "x86/entry: Stuff RSB for entry to kernel for non-SMEP platform"
>     - Revert "x86/mm: Only set IBPB when the new thread cannot ptrace current
>       thread"
>     - Revert "x86/mm: Set IBPB upon context switch"
>     - Revert "x86/idle: Disable IBRS when offlining cpu and re-enable on wakeup"
>     - Revert "x86/idle: Disable IBRS entering idle and enable it on wakeup"
>     - Revert "x86/enter: Use IBRS on syscall and interrupts"
>     - Revert "x86/enter: MACROS to set/clear IBRS and set IBPB"
>     - Revert "x86/feature: Report presence of IBPB and IBRS control"
>     - Revert "x86/feature: Enable the x86 feature to control Speculation"
>     - Revert "udf: prevent speculative execution"
>     - Revert "net: mpls: prevent speculative execution"
>     - Revert "fs: prevent speculative execution"
>     - Revert "ipv6: prevent speculative execution"
>     - Revert "userns: prevent speculative execution"
>     - Revert "Thermal/int340x: prevent speculative execution"
>     - Revert "cw1200: prevent speculative execution"
>     - Revert "qla2xxx: prevent speculative execution"
>     - Revert "p54: prevent speculative execution"
>     - Revert "carl9170: prevent speculative execution"
>     - Revert "uvcvideo: prevent speculative execution"
>     - Revert "x86, bpf, jit: prevent speculative execution when JIT is enabled"
>     - Revert "bpf: prevent speculative execution in eBPF interpreter"
>     - Revert "locking/barriers: introduce new memory barrier gmb()"
> 