lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 10 Aug 2021 01:43:06 +0800 From: Lai Jiangshan <jiangshanlai@...il.com> To: linux-kernel@...r.kernel.org Cc: Lai Jiangshan <laijs@...ux.alibaba.com>, Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org Subject: [PATCH V2 2/3] KVM: X86: Set the hardware DR6 only when KVM_DEBUGREG_WONT_EXIT From: Lai Jiangshan <laijs@...ux.alibaba.com> Commit c77fb5fe6f03 ("KVM: x86: Allow the guest to run with dirty debug registers") allows the guest accessing to DRs without exiting when KVM_DEBUGREG_WONT_EXIT and we need to ensure that they are synchronized on entry to the guest---including DR6 that was not synced before the commit. But the commit sets the hardware DR6 not only when KVM_DEBUGREG_WONT_EXIT, but also when KVM_DEBUGREG_BP_ENABLED. The second case is unnecessary and just leads to a more case which leaks stale DR6 to the host which has to be resolved by unconditionally reseting DR6 in kvm_arch_vcpu_put(). We'd better to set the hardware DR6 only when KVM_DEBUGREG_WONT_EXIT, so that we can fine-grain control the cases when we need to reset it which is done in later patch. Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com> --- arch/x86/kvm/x86.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ad47a09ce307..d2aa49722064 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9598,7 +9598,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) set_debugreg(vcpu->arch.eff_db[1], 1); set_debugreg(vcpu->arch.eff_db[2], 2); set_debugreg(vcpu->arch.eff_db[3], 3); - set_debugreg(vcpu->arch.dr6, 6); + /* When KVM_DEBUGREG_WONT_EXIT, dr6 is accessible in guest. */ + if (vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT) + set_debugreg(vcpu->arch.dr6, 6); } else if (unlikely(hw_breakpoint_active())) { set_debugreg(0, 7); } -- 2.19.1.6.gb485710b
Powered by blists - more mailing lists