** Changed in: linux (Ubuntu)
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1793451
Title:
mlock203 test in ubuntu_ltp_syscalls failed with Xenial kernel
Status in ubuntu-kernel-tests:
Fix Released
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Xenial:
Fix Released
Bug description:
== Justification ==
When one vma was with flag VM_LOCKED|VM_LOCKONFAULT (by invoking
mlock2(,MLOCK_ONFAULT)), it can again be populated with mlock() with
VM_LOCKED flag only.
There is a hole in mlock_fixup() which increase mm->locked_vm twice even
the two operations are on the same vma and both with VM_LOCKED flags.
The issue can be reproduced by following code:
mlock2(p, 1024 * 64, MLOCK_ONFAULT); //VM_LOCKED|VM_LOCKONFAULT
mlock(p, 1024 * 64); //VM_LOCKED
Then check the increase VmLck field in /proc/pid/status(to 128k).
When vma is set with different vm_flags, and the new vm_flags is with
VM_LOCKED, it is not necessarily be a "new locked" vma.
There is a dedicated reproducer, the "mlock203" test in
ubuntu_ltp_syscalls, you can see the failure for all the Ubuntu 4.4
kernel:
<<<test_start>>>
tag=mlock203 stime=1537369891
cmdline="mlock203"
contacts=""
analysis=exit
<<<test_output>>>
tst_test.c:1063: INFO: Timeout per run is 0h 05m 00s
mlock203.c:63: FAIL: Locking one memory again increased VmLck
Summary:
passed 0
failed 1
skipped 0
warnings 0
== Fix ==
b155b4fd (mm: mlock: avoid increase mm->locked_vm on mlock() when already
mlock2(,MLOCK_ONFAULT))
A test kernel for Xenial / Xenial-KVM could be found here:
http://people.canonical.com/~phlin/kernel/lp-1793451-mlock203/
== Regression Potential ==
Low, this patch prevents mm->locked_vm from increment just by adding an extra
check to see if the old vm_flags is already VM_LOCKED.
== Test Case ==
Run the mlock203 test in ubuntu_ltp_syscalls test suite. And it will pass
with the patched kernel.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-1068-aws 4.4.0-1068.78
ProcVersionSignature: User Name 4.4.0-1068.78-aws 4.4.144
Uname: Linux 4.4.0-1068-aws x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
Date: Thu Sep 20 06:44:13 2018
Ec2AMI: ami-0e32ec5bc225539f5
Ec2AMIManifest: (unknown)
Ec2AvailabilityZone: us-west-2b
Ec2InstanceType: c3.large
Ec2Kernel: unavailable
Ec2Ramdisk: unavailable
SourcePackage: linux-aws
UpgradeStatus: No upgrade log present (probably fresh install)
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