"ip a" command on a guest VM shows UNKNOWN status

[Eric Desrochers]

[Impact]

"ip a" command on a guest VM shows UNKNOWN status.

[Test Case]

* Environment : Running a guest VM with a virtio-net adaptor interface, running on DPDK.
* Perform "ip a" inside the guest VM shows state "UNKNOWN" as follow example:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
.....

[Regression Potential]

 * Regression is low, the patch fix the operstate logic for virtio when no VIRTIO_NET_F_STATUS.[1]
 * The patch has been first accepted in net-next, then move into Linus's git.

[1] - VIRTIO_NET_F_STATUS
Allow the host to inform us that the link is down by adding a VIRTIO_NET_F_STATUS which indicates that device status is available in virtio_net config.

[Other Info]

 * Linus: https://github.com/torvalds/linux/commit/bda7fab54828bbef2164bb23c0f6b1a7d05cc718

 * Net-next:
https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=bda7fab54828bbe

[Original Description]
It has been brought to our attention the following bug :

------------------------------------------------
Environment: The guest VM is using a canonical ubuntu image, and the eth0 is a virtio-net adaptor, running on DPDK.

Background: "ip a" command relies on the operstate variable of the net_device structure maintained by the kernel. This is based on the operational state as defined in the IF MIB (RFC 2863). Device drivers are expected to update this member. But many older drivers don’t seem to be using this. So in general, IF_OPER_UP and IF_OPER_UNKNOWN are treated as equal, in some sense, to maintain backward compatibility. Even if we look at https://elixir.free-electrons.com/linux/v4.15-rc2/source/include/linux/netdevice.h#L3468, the function to check if interface is up, is written as follows, which says that OPER_UNKNOWN is not something to be alarmed about, and just reflective of a state that some drivers don’t care to update about.

static inline bool netif_oper_up(const struct net_device *dev)
{
return (dev->operstate == IF_OPER_UP ||
dev->operstate == IF_OPER_UNKNOWN /* backward compat */);
}

Code Ref:

1. https://elixir.free-electrons.com/linux/v4.15-rc2/source/include/linux/netdevice.h#L1739
2. https://elixir.free-electrons.com/linux/v4.15-rc2/source/include/linux/netdevice.h#L3468
3. https://www.kernel.org/doc/Documentation/networking/operstates.txt

Now, for traditional kernel mode network adapter drivers, this state is supposed to be manipulated by the driver. And we can safely assume that most current kernel model drivers do keep this updated.
------------------------------------------------

[Eric Desrochers (slashd)]

For qemu and upstream DPDK, support is present for the VIRTIO_NET_F_STATUS capability, and as such should not experience the "UNKNOWN" operstate issue; jvosburgh checked qemu and don't see this issue when running it, but haven't set up DPDK to verify it's behavior.

The opencontrail vrouter source code does not support VIRTIO_NET_F_STATUS, which dovetails with the prior analysis that suggests that this lack of support would lead to the operstate UNKNOWN.

jvosburgh also examined the virtio specification itself. It indicates that if VIRTIO_NET_F_STATUS is not available, the "link should be assumed active."

[Eric Desrochers (slashd)]

The following patch fixes the bug :

-------------------
commit bda7fab54828bbef2164bb23c0f6b1a7d05cc718
Author: Jay Vosburgh <email address hidden>
Date: Thu Mar 22 14:42:41 2018 +0000

    virtio-net: Fix operstate for virtio when no VIRTIO_NET_F_STATUS

    The operstate update logic will leave an interface in the
    default UNKNOWN operstate if the interface carrier state never changes
    from the default carrier up state set at creation. This includes the
    case of an explicit call to netif_carrier_on, as the carrier on to on
    transition has no effect on operstate.

            This affects virtio-net for the case that the virtio peer does
    not support VIRTIO_NET_F_STATUS (the feature that provides carrier state
    updates). Without this feature, the virtio specification states that
    "the link should be assumed active," so, logically, the operstate should
    be UP instead of UNKNOWN. This has impact on user space applications
    that use the operstate to make availability decisions for the interface.

            Resolve this by changing the virtio probe logic slightly to call
    netif_carrier_off for both the "with" and "without" VIRTIO_NET_F_STATUS
    cases, and then the existing call to netif_carrier_on for the "without"
    case will cause an operstate transition.

    Cc: "Michael S. Tsirkin" <email address hidden>
    Cc: Jason Wang <email address hidden>
    Cc: Ben Hutchings <email address hidden>
    Signed-off-by: Jay Vosburgh <email address hidden>
    Acked-by: Michael S. Tsirkin <email address hidden>
    Signed-off-by: David S. Miller <email address hidden>
-------------------

[Eric Desrochers (slashd)]

https://github.com/torvalds/linux/commit/bda7fab54828bbef2164bb23c0f6b1a7d05cc718

[Eric Desrochers (slashd)]

Patch has been submitted to the Ubuntu kernel team ML

Subject:
[PATCH][SRU][B,A,X,T] virtio-net: Fix operstate for virtio when no VIRTIO_NET_F_STATUS

- Eric

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.15.0-19.20

---------------
linux (4.15.0-19.20) bionic; urgency=medium

  * linux: 4.15.0-19.20 -proposed tracker (LP: #1766021)

  * Kernel 4.15.0-15 breaks Dell PowerEdge 12th Gen servers (LP: #1765232)
    - Revert "blk-mq: simplify queue mapping & schedule with each possisble CPU"
    - Revert "genirq/affinity: assign vectors to all possible CPUs"

linux (4.15.0-18.19) bionic; urgency=medium

  * linux: 4.15.0-18.19 -proposed tracker (LP: #1765490)

  * [regression] Ubuntu 18.04:[4.15.0-17-generic #18] KVM Guest Kernel:
    meltdown: rfi/fallback displacement flush not enabled bydefault (kvm)
    (LP: #1765429)
    - powerpc/pseries: Fix clearing of security feature flags

  * signing: only install a signed kernel (LP: #1764794)
    - [Packaging] update to Debian like control scripts
    - [Packaging] switch to triggers for postinst.d postrm.d handling
    - [Packaging] signing -- switch to raw-signing tarballs
    - [Packaging] signing -- switch to linux-image as signed when available
    - [Config] signing -- enable Opal signing for ppc64el
    - [Packaging] printenv -- add signing options

  * [18.04 FEAT] Sign POWER host/NV kernels (LP: #1696154)
    - [Packaging] signing -- add support for signing Opal kernel binaries

  * Please cherrypick s390 unwind fix (LP: #1765083)
    - s390/compat: fix setup_frame32

  * Ubuntu 18.04 installer does not detect any IPR based HDD/RAID array [S822L]
    [ipr] (LP: #1751813)
    - d-i: move ipr to storage-core-modules on ppc64el

  * drivers/gpu/drm/bridge/adv7511/adv7511.ko missing (LP: #1764816)
    - SAUCE: (no-up) rename the adv7511 drm driver to adv7511_drm

  * Miscellaneous Ubuntu changes
    - [Packaging] Add linux-oem to rebuild test blacklist.

linux (4.15.0-17.18) bionic; urgency=medium

  * linux: 4.15.0-17.18 -proposed tracker (LP: #1764498)

  * Eventual OOM with profile reloads (LP: #1750594)
    - SAUCE: apparmor: fix memory leak when duplicate profile load

linux (4.15.0-16.17) bionic; urgency=medium

  * linux: 4.15.0-16.17 -proposed tracker (LP: #1763785)

  * [18.04] [bug] CFL-S(CNP)/CNL GPIO testing failed (LP: #1757346)
    - [Config]: Set CONFIG_PINCTRL_CANNONLAKE=y

  * [Ubuntu 18.04] USB Type-C test failed on GLK (LP: #1758797)
    - SAUCE: usb: typec: ucsi: Increase command completion timeout value

  * Fix trying to "push" an already active pool VP (LP: #1763386)
    - SAUCE: powerpc/xive: Fix trying to "push" an already active pool VP

  * hisi_sas: Revert and replace SAUCE patches w/ upstream (LP: #1762824)
    - Revert "UBUNTU: SAUCE: scsi: hisi_sas: export device table of v3 hw to
      userspace"
    - Revert "UBUNTU: SAUCE: scsi: hisi_sas: config for hip08 ES"
    - scsi: hisi_sas: modify some register config for hip08
    - scsi: hisi_sas: add v3 hw MODULE_DEVICE_TABLE()

  * Realtek card reader - RTS5243 [VEN_10EC&DEV_5260] (LP: #1737673)
    - misc: rtsx: Move Realtek Card Reader Driver to misc
    - updateconfigs for Realtek Card Reader Driver
    - misc: rtsx: Add support for RTS5260
    - misc: rtsx: Fix symbol clashes

  * Mellanox [mlx5] [bionic] UBSAN: Undefined behaviour in
    ./include/linux/net_dim.h (LP: #1...

[Brad Figg (brad-figg)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-trusty' to 'verification-done-trusty'. If the problem still exists, change the tag 'verification-needed-trusty' to 'verification-failed-trusty'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Brad Figg (brad-figg)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-artful' to 'verification-done-artful'. If the problem still exists, change the tag 'verification-needed-artful' to 'verification-failed-artful'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Brad Figg (brad-figg)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-xenial' to 'verification-done-xenial'. If the problem still exists, change the tag 'verification-needed-xenial' to 'verification-failed-xenial'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.13.0-149.199

---------------
linux (3.13.0-149.199) trusty; urgency=medium

  * CVE-2018-3639 (powerpc)
    - SAUCE: rfi-flush: update H_CPU_* macro names to upstream
    - SAUCE: rfi-flush: update plpar_get_cpu_characteristics() signature to
      upstream
    - powerpc/pseries: Support firmware disable of RFI flush
    - powerpc/powernv: Support firmware disable of RFI flush
    - powerpc/64s: Allow control of RFI flush via debugfs
    - powerpc/rfi-flush: Move the logic to avoid a redo into the debugfs code
    - powerpc/rfi-flush: Always enable fallback flush on pseries
    - powerpc/rfi-flush: Differentiate enabled and patched flush types
    - powerpc/pseries: Add new H_GET_CPU_CHARACTERISTICS flags
    - powerpc: Add security feature flags for Spectre/Meltdown
    - powerpc/pseries: Set or clear security feature flags
    - powerpc/powernv: Set or clear security feature flags
    - powerpc/powernv: Use the security flags in pnv_setup_rfi_flush()
    - powerpc/pseries: Use the security flags in pseries_setup_rfi_flush()
    - powerpc/pseries: Fix clearing of security feature flags
    - powerpc: Move default security feature flags
    - powerpc/pseries: Restore default security feature flags on setup
    - powerpc/64s: Add support for a store forwarding barrier at kernel entry/exit
    - SAUCE: powerpc/64s: Move the data access exception out-of-line

  * CVE-2018-3639 (x86)
    - arch: Introduce post-init read-only memory
    - SAUCE: Add X86_FEATURE_ARCH_CAPABILITIES
    - SAUCE: x86: Add alternative_msr_write
    - x86/nospec: Simplify alternative_msr_write()
    - x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
    - x86/bugs: Concentrate bug detection into a separate function
    - x86/bugs: Concentrate bug reporting into a separate function
    - x86/msr: Add definitions for new speculation control MSRs
    - x86/bugs: Read SPEC_CTRL MSR during boot and re-use reserved bits
    - x86/bugs, KVM: Support the combination of guest and host IBRS
    - x86/bugs: Expose /sys/../spec_store_bypass
    - x86/cpufeatures: Add X86_FEATURE_RDS
    - x86/bugs: Provide boot parameters for the spec_store_bypass_disable
      mitigation
    - x86/bugs/intel: Set proper CPU features and setup RDS
    - x86/bugs: Whitelist allowed SPEC_CTRL MSR values
    - x86/bugs/AMD: Add support to disable RDS on Fam[15,16,17]h if requested
    - x86/KVM/VMX: Expose SPEC_CTRL Bit(2) to the guest
    - x86/speculation: Create spec-ctrl.h to avoid include hell
    - prctl: Add speculation control prctls
    - x86/process: Allow runtime control of Speculative Store Bypass
    - x86/speculation: Add prctl for Speculative Store Bypass mitigation
    - nospec: Allow getting/setting on non-current task
    - proc: Provide details on speculation flaw mitigations
    - seccomp: Enable speculation flaw mitigations
    - SAUCE: x86/bugs: Honour SPEC_CTRL default
    - x86/bugs: Make boot modes __ro_after_init
    - prctl: Add force disable speculation
    - seccomp: Use PR_SPEC_FORCE_DISABLE
    - seccomp: Add filter flag to opt-out of SSB mitigation
    - seccomp: Move speculation migitation control to ar...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.4.0-127.153

---------------
linux (4.4.0-127.153) xenial; urgency=medium

  * CVE-2018-3639 (powerpc)
    - powerpc/pseries: Support firmware disable of RFI flush
    - powerpc/powernv: Support firmware disable of RFI flush
    - powerpc/rfi-flush: Move the logic to avoid a redo into the debugfs code
    - powerpc/rfi-flush: Make it possible to call setup_rfi_flush() again
    - powerpc/rfi-flush: Always enable fallback flush on pseries
    - powerpc/rfi-flush: Differentiate enabled and patched flush types
    - powerpc/rfi-flush: Call setup_rfi_flush() after LPM migration
    - powerpc/pseries: Add new H_GET_CPU_CHARACTERISTICS flags
    - powerpc: Add security feature flags for Spectre/Meltdown
    - powerpc/pseries: Set or clear security feature flags
    - powerpc/powernv: Set or clear security feature flags
    - powerpc/64s: Move cpu_show_meltdown()
    - powerpc/64s: Enhance the information in cpu_show_meltdown()
    - powerpc/powernv: Use the security flags in pnv_setup_rfi_flush()
    - powerpc/pseries: Use the security flags in pseries_setup_rfi_flush()
    - powerpc/64s: Wire up cpu_show_spectre_v1()
    - powerpc/64s: Wire up cpu_show_spectre_v2()
    - powerpc/pseries: Fix clearing of security feature flags
    - powerpc: Move default security feature flags
    - powerpc/pseries: Restore default security feature flags on setup
    - SAUCE: powerpc/64s: Add support for a store forwarding barrier at kernel
      entry/exit

  * CVE-2018-3639 (x86)
    - SAUCE: Clean up IBPB and IBRS control functions and macros
    - SAUCE: Fix up IBPB and IBRS kernel parameters documentation
    - SAUCE: Remove #define X86_FEATURE_PTI
    - x86/cpufeature: Move some of the scattered feature bits to x86_capability
    - x86/cpufeature: Cleanup get_cpu_cap()
    - x86/cpu: Probe CPUID leaf 6 even when cpuid_level == 6
    - x86/cpufeatures: Add CPUID_7_EDX CPUID leaf
    - x86/cpufeatures: Add Intel feature bits for Speculation Control
    - SAUCE: x86/kvm: Expose SPEC_CTRL from the leaf
    - x86/cpufeatures: Add AMD feature bits for Speculation Control
    - x86/msr: Add definitions for new speculation control MSRs
    - SAUCE: x86/msr: Rename MSR spec control feature bits
    - x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
    - x86/cpufeature: Blacklist SPEC_CTRL/PRED_CMD on early Spectre v2 microcodes
    - x86/speculation: Add basic IBPB (Indirect Branch Prediction Barrier) support
    - x86/speculation: Add <asm/msr-index.h> dependency
    - x86/cpufeatures: Clean up Spectre v2 related CPUID flags
    - x86/cpuid: Fix up "virtual" IBRS/IBPB/STIBP feature bits on Intel
    - SAUCE: x86/speculation: Move vendor specific IBRS/IBPB control code
    - SAUCE: x86: Add alternative_msr_write
    - SAUCE: x86/nospec: Simplify alternative_msr_write()
    - SAUCE: x86/bugs: Concentrate bug detection into a separate function
    - SAUCE: x86/bugs: Concentrate bug reporting into a separate function
    - arch: Introduce post-init read-only memory
    - SAUCE: x86/bugs: Read SPEC_CTRL MSR during boot and re-use reserved bits
    - SAUCE: x86/bugs, KVM: Support the combination of guest a...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 4.13.0-43.48

---------------
linux (4.13.0-43.48) artful; urgency=medium

  * CVE-2018-3639 (powerpc)
    - SAUCE: rfi-flush: update H_CPU_* macro names to upstream
    - SAUCE: rfi-flush: update plpar_get_cpu_characteristics() signature to
      upstream
    - SAUCE: update pseries_setup_rfi_flush() capitalization to upstream
    - powerpc/pseries: Support firmware disable of RFI flush
    - powerpc/powernv: Support firmware disable of RFI flush
    - powerpc/64s: Allow control of RFI flush via debugfs
    - powerpc/rfi-flush: Move the logic to avoid a redo into the debugfs code
    - powerpc/rfi-flush: Always enable fallback flush on pseries
    - powerpc/rfi-flush: Differentiate enabled and patched flush types
    - powerpc/pseries: Add new H_GET_CPU_CHARACTERISTICS flags
    - powerpc: Add security feature flags for Spectre/Meltdown
    - powerpc/powernv: Set or clear security feature flags
    - powerpc/pseries: Set or clear security feature flags
    - powerpc/powernv: Use the security flags in pnv_setup_rfi_flush()
    - powerpc/pseries: Use the security flags in pseries_setup_rfi_flush()
    - powerpc/pseries: Fix clearing of security feature flags
    - powerpc: Move default security feature flags
    - powerpc/pseries: Restore default security feature flags on setup
    - powerpc/64s: Add support for a store forwarding barrier at kernel entry/exit

  * CVE-2018-3639 (x86)
    - SAUCE: Add X86_FEATURE_ARCH_CAPABILITIES
    - SAUCE: x86: Add alternative_msr_write
    - x86/nospec: Simplify alternative_msr_write()
    - x86/pti: Do not enable PTI on CPUs which are not vulnerable to Meltdown
    - x86/bugs: Concentrate bug detection into a separate function
    - x86/bugs: Concentrate bug reporting into a separate function
    - x86/msr: Add definitions for new speculation control MSRs
    - x86/bugs: Read SPEC_CTRL MSR during boot and re-use reserved bits
    - x86/bugs, KVM: Support the combination of guest and host IBRS
    - x86/bugs: Expose /sys/../spec_store_bypass
    - x86/cpufeatures: Add X86_FEATURE_RDS
    - x86/bugs: Provide boot parameters for the spec_store_bypass_disable
      mitigation
    - x86/bugs/intel: Set proper CPU features and setup RDS
    - x86/bugs: Whitelist allowed SPEC_CTRL MSR values
    - x86/bugs/AMD: Add support to disable RDS on Fam[15,16,17]h if requested
    - x86/KVM/VMX: Expose SPEC_CTRL Bit(2) to the guest
    - x86/speculation: Create spec-ctrl.h to avoid include hell
    - prctl: Add speculation control prctls
    - x86/process: Allow runtime control of Speculative Store Bypass
    - x86/speculation: Add prctl for Speculative Store Bypass mitigation
    - nospec: Allow getting/setting on non-current task
    - proc: Provide details on speculation flaw mitigations
    - seccomp: Enable speculation flaw mitigations
    - SAUCE: x86/bugs: Honour SPEC_CTRL default
    - x86/bugs: Make boot modes __ro_after_init
    - prctl: Add force disable speculation
    - seccomp: Use PR_SPEC_FORCE_DISABLE
    - seccomp: Add filter flag to opt-out of SSB mitigation
    - seccomp: Move speculation migitation control to arch code
    - x86/speculation: Make "seccomp" the...

[Brad Figg (brad-figg)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-bionic' to 'verification-done-bionic'. If the problem still exists, change the tag 'verification-needed-bionic' to 'verification-failed-bionic'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Andy Whitcroft (apw)]

This bug was erroneously marked for verification in bionic; verification is not required and verification-needed-bionic is being removed.