Paolo Bonzini <pbonzini@xxxxxxxxxx> 于2019年11月12日周二 下午10:23写道： > > CVE-2018-12207 is a microarchitectural implementation issue > that could allow an unprivileged local attacker to cause system wide > denial-of-service condition. > > Privileged software may change the page size (ex. 4KB, 2MB, 1GB) in the > paging structures, without following such paging structure changes with > invalidation of the TLB entries corresponding to the changed pages. In > this case, the attacker could invoke instruction fetch, which will result > in the processor hitting multiple TLB entries, reporting a machine check > error exception, and ultimately hanging the system. > > The attached patches mitigate the vulnerability by making huge pages > non-executable. The processor will not be able to execute an instruction > residing in a large page (ie. 2MB, 1GB, etc.) without causing a trap into > the host kernel/hypervisor; KVM will then break the large page into 4KB > pages and gives executable permission to 4KB pages. > > Thanks to everyone that was involved in the development of these patches, > especially Junaid Shahid, who provided the first version of the code, > and Thomas Gleixner. > > Paolo Hi Paolo, hi list, Thanks for info, do we need qemu patch for full mitigation? Debian mentioned: https://linuxsecurity.com/advisories/debian/debian-dsa-4566-1-qemu-security-update-17-10-10 " A qemu update adding support for the PSCHANGE_MC_NO feature, which allows to disable iTLB Multihit mitigations in nested hypervisors will be provided via DSA 4566-1. " But It's not yet available publicly. About the performance hit, do you know any number? probably the answer is workload dependent. Regards, Jack Wang
