[PATCH RESEND] kvm: Fix nonsense handling of compat ioctl

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

From: Alan Cox <alan@linux.intel.com>

KVM_SET_SIGNAL_MASK passed a NULL argument leaves the on stack signal
sets uninitialized. It then passes them through to
kvm_vcpu_ioctl_set_sigmask.

We should be passing a NULL in this case not translated garbage.

Signed-off-by: Alan Cox <alan@linux.intel.com>
---

 virt/kvm/kvm_main.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index a2e85af..e47a7ca 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1975,9 +1975,10 @@ static long kvm_vcpu_compat_ioctl(struct file *filp,
 			if (copy_from_user(&csigset, sigmask_arg->sigset,
 					   sizeof csigset))
 				goto out;
-		}
-		sigset_from_compat(&sigset, &csigset);
-		r = kvm_vcpu_ioctl_set_sigmask(vcpu, &sigset);
+			sigset_from_compat(&sigset, &csigset);
+			r = kvm_vcpu_ioctl_set_sigmask(vcpu, &sigset);
+		} else
+			kvm_vcpu_ioctl_set_sigmask(vcpu, NULL);
 		break;
 	}
 	default: