------- Comment From heinz-werner_se...@de.ibm.com 2018-12-03 11:02 EDT------- IBM Bugzilla Status -> closed, Fix Released by Xenial, Bionic, Cosmic
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1800849 Title: [Ubuntu] kvm: fix deadlock when killed by oom Status in Ubuntu on IBM z Systems: Fix Released Status in linux package in Ubuntu: Fix Released Status in linux source package in Xenial: Fix Released Status in linux source package in Bionic: Fix Released Status in linux source package in Cosmic: Fix Released Bug description: == SRU Justification == Description: kvm: fix deadlock when killed by oom Symptom: oom killer leaves processes in a deadlock state. Problem: The problem arises in the rare cases in which handle_mm_fault does not release the mm_sem. Solution: Correct the issue by manually release the mm_sem when needed. == Fix == 306d6c49ac9ded11114cb53b0925da52f2c2ada1 ("s390/kvm: fix deadlock when killed by oom") == Patch == commit 306d6c49ac9ded11114cb53b0925da52f2c2ada1 Author: Claudio Imbrenda <imbre...@linux.vnet.ibm.com> Date: Mon Jul 16 10:38:57 2018 +0200 s390/kvm: fix deadlock when killed by oom When the oom killer kills a userspace process in the page fault handler while in guest context, the fault handler fails to release the mm_sem if the FAULT_FLAG_RETRY_NOWAIT option is set. This leads to a deadlock when tearing down the mm when the process terminates. This bug can only happen when pfault is enabled, so only KVM clients are affected. The problem arises in the rare cases in which handle_mm_fault does not release the mm_sem. This patch fixes the issue by manually releasing the mm_sem when needed. Fixes: 24eb3a824c4f3 ("KVM: s390: Add FAULT_FLAG_RETRY_NOWAIT for guest fault") Cc: <sta...@vger.kernel.org> # 3.15+ Signed-off-by: Claudio Imbrenda <imbre...@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidef...@de.ibm.com> == Regression Potential == Low and minimal, because: - code change is s390x only - limited to one single file: /arch/s390/mm/fault.c - just two additional lines added (if stmt) - Xenial and Cosmic already have this commit via upstream stable updates. - Hence patch is just missing in Bionic. - Test kernel was build for testting. == Test Case == Create numerous KVM guests so that the host starts swapping and memory becomes overcomitted and the oom killer is triggered. __________ Description: kvm: fix deadlock when killed by oom Symptom: oom killer leaves processes in a deadlock state. Problem: The problem arises in the rare cases in which handle_mm_fault does not release the mm_sem. Solution: Correct the issue by manually relaese the mm_sem when needed. Reproduction: Create numerous KVM guests so that the host starts swapping and memory becomes overcomitted and the oom killer is triggered. kernel 4.19 Upstream-ID: 306d6c49ac9ded11114cb53b0925da52f2c2ada1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-z-systems/+bug/1800849/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
