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kvm: x86: fix KVM_XEN_HVM_CONFIG ioctl

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[ Upstream commit 51776043af ]

This ioctl is obsolete (it was used by Xenner as far as I know) but
still let's not break it gratuitously...  Its handler is copying
directly into struct kvm.  Go through a bounce buffer instead, with
the added benefit that we can actually do something useful with the
flags argument---the previous code was exiting with -EINVAL but still
doing the copy.

This technically is a userspace ABI breakage, but since no one should be
using the ioctl, it's a good occasion to see if someone actually
complains.

Cc: kernel-hardening@lists.openwall.com
Cc: Kees Cook <keescook@chromium.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paolo Bonzini 2017-10-26 15:45:47 +02:00 committed by Greg Kroah-Hartman
parent 7c11bd3dc8
commit ff49a37253
1 changed files with 4 additions and 3 deletions
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7
arch/x86/kvm/x86.c
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@ -3973,13 +3973,14 @@ long kvm_arch_vm_ioctl(struct file *filp,
mutex_unlock(&kvm->lock);
break;
case KVM_XEN_HVM_CONFIG: {
struct kvm_xen_hvm_config xhc;
r = -EFAULT;
if (copy_from_user(&kvm->arch.xen_hvm_config, argp,
sizeof(struct kvm_xen_hvm_config)))
if (copy_from_user(&xhc, argp, sizeof(xhc)))
goto out;
r = -EINVAL;
if (kvm->arch.xen_hvm_config.flags)
if (xhc.flags)
goto out;
memcpy(&kvm->arch.xen_hvm_config, &xhc, sizeof(xhc));
r = 0;
break;
}