The gs_index loading code uses the swapgs instruction to switch to the user gs_base temporarily. This is unsave in an lightweight exit-path in KVM on AMD because the KERNEL_GS_BASE MSR is switches lazily. An NMI happening in the critical path of load_gs_index may use the wrong GS_BASE value then leading to unpredictable behavior, e.g. a triple-fault. This patch fixes the issue by making sure that load_gs_index is called only with a valid KERNEL_GS_BASE value loaded in KVM.
Cc: [email protected] Signed-off-by: Joerg Roedel <[email protected]> --- arch/x86/kvm/svm.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 25bd1bc..54ce246 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -1150,8 +1150,8 @@ static void svm_vcpu_put(struct kvm_vcpu *vcpu) kvm_load_ldt(svm->host.ldt); #ifdef CONFIG_X86_64 loadsegment(fs, svm->host.fs); - load_gs_index(svm->host.gs); wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs); + load_gs_index(svm->host.gs); #else loadsegment(gs, svm->host.gs); #endif -- 1.7.1 _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
