Date: Sun, 7 Oct 2018 08:04:51 +0200 From: Salvatore Bonaccorso <carnil@...ian.org> To: OSS Security Mailinglist <oss-security@...ts.openwall.com> Cc: Will Deacon <will.deacon@....com>, marc.zyngier@....com Subject: Re: arm64 Linux kernel: Privilege escalation by taking control of the KVM hypervisor Hi, On Tue, Oct 02, 2018 at 05:07:14PM +0100, Will Deacon wrote: > Hi all, > > Whilst reviewing some proposed arm64 KVM changes, it became apparent that > the sanity checking for the KVM_SET_ON_REG ioctl() on arm64 does not > correctly handle a number of cases: > > - Unaligned register accesses and accesses that span multiple > registers can bypass PSTATE sanity checking > > - The PSTATE sanity checking fails to take into account the > capabilities of the physical CPU, or the configuration of > the virtual CPU > > This allows an attacker with permission to create KVM-based virtual machines > to both panic the hypervisor by triggering an illegal exception return > (resulting in a DoS) and to redirect execution elsewhere within the > hypervisor with full register control, instead of causing a return to the > guest. > > This has been fixed by upstream commits: > > d26c25a9d19b ("arm64: KVM: Tighten guest core register access from userspace") > 2a3f93459d68 ("arm64: KVM: Sanitize PSTATE.M when being set from userspace") > > which are being backported and applied to all active -stable kernels. > > 32-bit Arm is unaffected by this issue. > > There has not yet been a CVE requested for this (mainly because I don't know > how to do it). This issue got CVE-2018-18021 assigned. Regards, Salvatore
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