Am 30.10.2010 16:11, Vasiliy Kulikov wrote:
> Structure kvm_ppc_pvinfo is copied to userland with pad field
> unitialized. Structure kvm_clock_data is copied to userland with
> flags and pad fields unitialized. It leads to leaking of contents
> of kernel stack memory.
This description only partially matches your patch, please fix.
>
> Signed-off-by: Vasiliy Kulikov <segooon@xxxxxxxxx>
> ---
> I cannot compile this driver, so it is not tested at all.
Why? It should be compilable (provided you have a x86 toolchain).
>
> As it is not compilable, I've missed and typed wrong var name in v1, sorry.
>
> arch/x86/kvm/x86.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b0818f6..261f3d0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2896,6 +2896,7 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
> case KVM_GET_DEBUGREGS: {
> struct kvm_debugregs dbgregs;
>
> + memset(&dbgregs, 0, sizeof(dbgregs));
> kvm_vcpu_ioctl_x86_get_debugregs(vcpu, &dbgregs);
>
> r = -EFAULT;
> @@ -3481,11 +3482,11 @@ long kvm_arch_vm_ioctl(struct file *filp,
> struct kvm_clock_data user_ns;
> u64 now_ns;
>
> + memset(&user_ns, 0, sizeof(user_ns));
> local_irq_disable();
> now_ns = get_kernel_ns();
> user_ns.clock = kvm->arch.kvmclock_offset + now_ns;
> local_irq_enable();
> - user_ns.flags = 0;
>
> r = -EFAULT;
> if (copy_to_user(argp, &user_ns, sizeof(user_ns)))
I would rather clear the padding/reserved fields (in both cases). No
need to double-initialize properly set fields.
There are more interfaces in KVM for obtaining data from the kernel via
padded structures. Did you check them all (kvm_vcpu_events come to my mind)?
Nevertheless, looks like a worthwhile hardening of the KVM interfaces.
Thanks,
Jan
Attachment:
signature.asc
Description: OpenPGP digital signature
