Ubuntu
linux-azure package

Azure 5.4: vDSO broken with 5.4.0-1075-azure

Bug #1977753 reported by Tim Gardner
12
This bug affects 2 people
Affects Status Importance Assigned to Milestone
linux-azure (Ubuntu)
Fix Released
Undecided
Unassigned
Focal
Fix Released
Medium
Tim Gardner

Bug Description

SRU Justification

[Impact]
vDSO works with the 5.4.0-1074-azure kernel, but is broken in 5.4.0-1075-azure and newer due to this commit
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/bionic/commit/?h=Ubuntu-azure-5.4-5.4.0-1075.78_18.04.1&id=5c899e1bcda02c755a5327353ed66f0768771644

Please revert the commit 5c899e1bcda02c755a5327353ed66f0768771644.

How to verify vDSO is working: "strace date 2>&1 | grep time" should not show the time related syscalls, e.g. clock_gettime()
With 5.4.0-1075-azure and newer, I see the time related syscalls.

****************************************************************
More info:
The buggy commit 5c899e1bcda02c755a5327353ed66f0768771644 was backported from the mainline commit:
e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences inline")
but due to the differences between the mainline kernel and the 5.4.0-107x-azure kernel, we actually should not simply remove hv_set_clocksource_vdso().

FWIW, the mainline commit is actually buggy and is fixed by this later mainline path:

commit 3486d2c9be652a31033363bdd50391b0c8a8fe21
Author: Vitaly Kuznetsov <email address hidden>
Date: Thu May 13 09:32:46 2021 +0200

clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE_HVCLOCK on X86

Mohammed reports (https://bugzilla.kernel.org/show_bug.cgi?id=213029)
the commit e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO
differences inline") broke vDSO on x86. The problem appears to be that
VDSO_CLOCKMODE_HVCLOCK is an enum value in 'enum vdso_clock_mode' and
'#ifdef VDSO_CLOCKMODE_HVCLOCK' branch evaluates to false (it is not
a define).

Use a dedicated HAVE_VDSO_CLOCKMODE_HVCLOCK define instead.

Fixes: e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences inline")
Reported-by: Mohammed Gamal <email address hidden>
Suggested-by: Thomas Gleixner <email address hidden>
Signed-off-by: Vitaly Kuznetsov <email address hidden>
Signed-off-by: Thomas Gleixner <email address hidden>
Reviewed-by: Michael Kelley <email address hidden>
Link: https://<email address hidden>

PS, Ubunt 20.04’s 5.13.0-1026-azure is not affected.

After some discussion it was decided that the revert is the best solution.

[Test Case]

strace date 2>&1 | grep time
also Microsoft tested

[Where things could go wrong]

vDSO entry point could stop working altogether

[Other Info]

SF: #00338309

See original description

CVE References

Tim Gardner (timg-tpi)
affects: linux (Ubuntu) → linux-azure (Ubuntu)
Changed in linux-azure (Ubuntu):
status: New → Fix Released
Changed in linux-azure (Ubuntu Focal):
assignee: nobody → Tim Gardner (timg-tpi)
importance: Undecided → Medium
status: New → In Progress
description: updated
Revision history for this message
Tim Gardner (timg-tpi) wrote :

Revert submitted: https://lists.ubuntu.com/archives/kernel-team/2022-June/130860.html

Tim Gardner (timg-tpi)
Changed in linux-azure (Ubuntu Focal):
status: In Progress → Fix Committed
Revision history for this message
Ubuntu Kernel Bot (ubuntu-kernel-bot) wrote :

This bug is awaiting verification that the linux-azure/5.4.0-1086.91 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-focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'.

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!

tags: added: verification-needed-focal
Revision history for this message
Tim Gardner (timg-tpi) wrote :

Microsoft tested

tags: added: verification-done-focal
removed: verification-needed-focal
Revision history for this message
Launchpad Janitor (janitor) wrote :
Download full text (16.2 KiB)

This bug was fixed in the package linux-azure - 5.4.0-1086.91

---------------
linux-azure (5.4.0-1086.91) focal; urgency=medium

  * focal/linux-azure: 5.4.0-1086.91 -proposed tracker (LP: #1979462)

  * Focal update: upstream stable patchset v5.4.192 (LP: #1979014)
    - [Config] azure: updateconfigs for NVM, NVM_PBLK

  * focal/azure: The console log of ARM64 Ubuntu 18.04 has duplicate output
    (LP: #1976399)
    - printk: Move console matching logic into a separate function
    - printk: Fix preferred console selection with multiple matches

  * nbd: requests can become stuck when disconnecting from server with qemu-nbd
    (LP: #1896350)
    - blk-mq: blk-mq: provide forced completion method
    - blk-mq: move failure injection out of blk_mq_complete_request
    - nbd: don't handle response without a corresponding request message
    - nbd: make sure request completion won't concurrent
    - nbd: don't clear 'NBD_CMD_INFLIGHT' flag if request is not completed
    - nbd: fix io hung while disconnecting device

  * Azure 5.4: vDSO broken with 5.4.0-1075-azure (LP: #1977753)
    - Revert "clocksource/drivers/hyper-v: Handle vDSO differences inline"

  [ Ubuntu: 5.4.0-122.138 ]

  * focal/linux: 5.4.0-122.138 -proposed tracker (LP: #1979489)
  * Remove SAUCE patches from test_vxlan_under_vrf.sh in net of
    ubuntu_kernel_selftests (LP: #1975691)
    - Revert "UBUNTU: SAUCE: selftests: net: Don't fail test_vxlan_under_vrf on
      xfail"
    - Revert "UBUNTU: SAUCE: selftests: net: Make test for VXLAN underlay in non-
      default VRF an expected failure"
  * Enable Asus USB-BT500 Bluetooth dongle(0b05:190e) (LP: #1976613)
    - Bluetooth: btusb: Add flag to define wideband speech capability
    - Bluetooth: btrtl: Add support for RTL8761B
    - Bluetooth: btusb: Add 0x0b05:0x190e Realtek 8761BU (ASUS BT500) device.
  * [UBUNTU 20.04] rcu stalls with many storage key guests (LP: #1975582)
    - s390/gmap: voluntarily schedule during key setting
    - s390/mm: use non-quiescing sske for KVM switch to keyed guest
  * Ubuntu 5.4.0-117.132-generic 5.4.189 has BUG: kernel NULL pointer
    dereference, address: 0000000000000034 (LP: #1978719)
    - mm: rmap: explicitly reset vma->anon_vma in unlink_anon_vmas()
  * Focal update: upstream stable patchset v5.4.192 (LP: #1979014)
    - floppy: disable FDRAWCMD by default
    - [Config] updateconfigs for BLK_DEV_FD_RAWCMD
    - hamradio: defer 6pack kfree after unregister_netdev
    - hamradio: remove needs_free_netdev to avoid UAF
    - lightnvm: disable the subsystem
    - [Config] updateconfigs for NVM, NVM_PBLK
    - usb: mtu3: fix USB 3.0 dual-role-switch from device to host
    - USB: quirks: add a Realtek card reader
    - USB: quirks: add STRING quirk for VCOM device
    - USB: serial: whiteheat: fix heap overflow in WHITEHEAT_GET_DTR_RTS
    - USB: serial: cp210x: add PIDs for Kamstrup USB Meter Reader
    - USB: serial: option: add support for Cinterion MV32-WA/MV32-WB
    - USB: serial: option: add Telit 0x1057, 0x1058, 0x1075 compositions
    - xhci: stop polling roothubs after shutdown
    - xhci: increase usb U3 -> U0 link resume timeout from 100ms to 500ms
    - iio: dac: ad5592r: Fix...

Changed in linux-azure (Ubuntu Focal):
status: Fix Committed → Fix Released
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