| Message ID | 20210917120329.2013766-1-eesposit@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: nSVM: avoid TOC/TOU race when checking vmcb12 | expand |
On 17/09/21 14:03, Emanuele Giuseppe Esposito wrote: > Currently there is a TOC/TOU race between the check of vmcb12's > efer, cr0 and cr4 registers and the later save of their values in > svm_set_*, because the guest could modify the values in the meanwhile. > > To solve this issue, this serie introuces and uses svm->nested.save > structure in enter_svm_guest_mode to save the current value of efer, > cr0 and cr4 and later use these to set the vcpu->arch.* state. > > Patch 1 just refactor the code to simplify the next two patches, > patch 2 introduces svm->nested.save to cache the efer, cr0 and cr4 fields > and in patch 3 and 4 we use it to avoid TOC/TOU races. > > Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> Most of my remarks from the RFC still apply, so I will wait for v3. Thanks, and sorry for the time between send and review. Paolo
Currently there is a TOC/TOU race between the check of vmcb12's efer, cr0 and cr4 registers and the later save of their values in svm_set_*, because the guest could modify the values in the meanwhile. To solve this issue, this serie introuces and uses svm->nested.save structure in enter_svm_guest_mode to save the current value of efer, cr0 and cr4 and later use these to set the vcpu->arch.* state. Patch 1 just refactor the code to simplify the next two patches, patch 2 introduces svm->nested.save to cache the efer, cr0 and cr4 fields and in patch 3 and 4 we use it to avoid TOC/TOU races. Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com> --- RFC: * use svm->nested.save instead of local variables. * not dependent anymore from "KVM: nSVM: remove useless kvm_clear_*_queue" * simplified patches, we just use the struct and not move the check nearer to the TOU. v2: * svm->nested.save is a separate struct vmcb_save_area_cached, and not vmcb_save_area. * update also vmcb02->cr3 with svm->nested.save.cr3 Emanuele Giuseppe Esposito (4): KVM: nSVM: move nested_vmcb_check_cr3_cr4 logic in nested_vmcb_valid_sregs nSVM: introduce smv->nested.save to cache save area fields nSVM: use vmcb_save_area_cached in nested_vmcb_valid_sregs() nSVM: use svm->nested.save to load vmcb12 registers and avoid TOC/TOU races arch/x86/kvm/svm/nested.c | 95 +++++++++++++++++++++------------------ arch/x86/kvm/svm/svm.c | 1 + arch/x86/kvm/svm/svm.h | 12 +++++ 3 files changed, 64 insertions(+), 44 deletions(-)