Azure 5.4: vDSO broken with 5.4.0-1075-azure
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:/
Please revert the commit 5c899e1bcda02c7
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 5c899e1bcda02c7
e4ab4658f1cf ("clocksource/
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_
FWIW, the mainline commit is actually buggy and is fixed by this later mainline path:
commit 3486d2c9be652a3
Author: Vitaly Kuznetsov <email address hidden>
Date: Thu May 13 09:32:46 2021 +0200
clocksource/
Mohammed reports (https:/
the commit e4ab4658f1cf ("clocksource/
differences inline") broke vDSO on x86. The problem appears to be that
VDSO_CLOCKMODE_
'#ifdef VDSO_CLOCKMODE_
a define).
Use a dedicated HAVE_VDSO_
Fixes: e4ab4658f1cf ("clocksource/
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
CVE References
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 |
Changed in linux-azure (Ubuntu Focal): | |
status: | In Progress → Fix Committed |
Revert submitted: https:/ /lists. ubuntu. com/archives/ kernel- team/2022- June/130860. html