commit 20b7035c66bacc909ae3ffe92c1a1ea7db99fe4f
author Jan H. Schönherr <jschoenh@amazon.de> Fri Nov 24 22:39:01 2017 +0100
committer Paolo Bonzini <pbonzini@redhat.com> Mon Nov 27 17:53:47 2017 +0100
tree 1d3ba8ee0b1f0caf975b1ce323be02e3c7682752
parent b74558259c5149e5edd79348b70eb34177cbeea0

KVM: Let KVM_SET_SIGNAL_MASK work as advertised

KVM API says for the signal mask you set via KVM_SET_SIGNAL_MASK, that
"any unblocked signal received [...] will cause KVM_RUN to return with
-EINTR" and that "the signal will only be delivered if not blocked by
the original signal mask".

This, however, is only true, when the calling task has a signal handler
registered for a signal. If not, signal evaluation is short-circuited for
SIG_IGN and SIG_DFL, and the signal is either ignored without KVM_RUN
returning or the whole process is terminated.

Make KVM_SET_SIGNAL_MASK behave as advertised by utilizing logic similar
to that in do_sigtimedwait() to avoid short-circuiting of signals.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

virt/kvm/kvm_main.c

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2dd1a9c..c01cff0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2065,6 +2065,29 @@
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_mark_page_dirty);
 
+void kvm_sigset_activate(struct kvm_vcpu *vcpu)
+{
+	if (!vcpu->sigset_active)
+		return;
+
+	/*
+	 * This does a lockless modification of ->real_blocked, which is fine
+	 * because, only current can change ->real_blocked and all readers of
+	 * ->real_blocked don't care as long ->real_blocked is always a subset
+	 * of ->blocked.
+	 */
+	sigprocmask(SIG_SETMASK, &vcpu->sigset, &current->real_blocked);
+}
+
+void kvm_sigset_deactivate(struct kvm_vcpu *vcpu)
+{
+	if (!vcpu->sigset_active)
+		return;
+
+	sigprocmask(SIG_SETMASK, &current->real_blocked, NULL);
+	sigemptyset(&current->real_blocked);
+}
+
 static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
 {
 	unsigned int old, val, grow;