** Description changed: == 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 + 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 called "mlock203" test in + 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 + <<<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 + 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)
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1793451 Title: mlock203 test in ubuntu_ltp_syscalls failed with Xenial kernel To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/1793451/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
