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authorPaolo Bonzini <pbonzini@redhat.com>2019-01-29 18:41:16 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2019-02-07 19:02:56 +0100
commit353c0956a618a07ba4bbe7ad00ff29fe70e8412a (patch)
tree700215bc94e83bb7f31e0ef3f9f6a59183257bec
parentcfa39381173d5f969daf43582c95ad679189cbc9 (diff)
downloadlinux-353c0956a618a07ba4bbe7ad00ff29fe70e8412a.tar.bz2
KVM: x86: work around leak of uninitialized stack contents (CVE-2019-7222)
Bugzilla: 1671930 Emulation of certain instructions (VMXON, VMCLEAR, VMPTRLD, VMWRITE with memory operand, INVEPT, INVVPID) can incorrectly inject a page fault when passed an operand that points to an MMIO address. The page fault will use uninitialized kernel stack memory as the CR2 and error code. The right behavior would be to abort the VM with a KVM_EXIT_INTERNAL_ERROR exit to userspace; however, it is not an easy fix, so for now just ensure that the error code and CR2 are zero. Embargoed until Feb 7th 2019. Reported-by: Felix Wilhelm <fwilhelm@google.com> Cc: stable@kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/x86.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3d27206f6c01..e67ecf25e690 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5116,6 +5116,13 @@ int kvm_read_guest_virt(struct kvm_vcpu *vcpu,
{
u32 access = (kvm_x86_ops->get_cpl(vcpu) == 3) ? PFERR_USER_MASK : 0;
+ /*
+ * FIXME: this should call handle_emulation_failure if X86EMUL_IO_NEEDED
+ * is returned, but our callers are not ready for that and they blindly
+ * call kvm_inject_page_fault. Ensure that they at least do not leak
+ * uninitialized kernel stack memory into cr2 and error code.
+ */
+ memset(exception, 0, sizeof(*exception));
return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access,
exception);
}