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Subject[PATCH v2 1/2] KVM: x86/xen: Initialize Xen timer only once
Date
Add a check for existing xen timers before initializing a new one.

Currently kvm_xen_init_timer() is called on every
KVM_XEN_VCPU_ATTR_TYPE_TIMER, which is causing the following ODEBUG
crash when vcpu->arch.xen.timer is already set.

ODEBUG: init active (active state 0)
object type: hrtimer hint: xen_timer_callbac0
RIP: 0010:debug_print_object+0x16e/0x250 lib/debugobjects.c:502
Call Trace:
__debug_object_init
debug_hrtimer_init
debug_init
hrtimer_init
kvm_xen_init_timer
kvm_xen_vcpu_set_attr
kvm_arch_vcpu_ioctl
kvm_vcpu_ioctl
vfs_ioctl

Link: https://syzkaller.appspot.com/bug?id=8234a9dfd3aafbf092cc5a7cd9842e3ebc45fc42
Reported-by: syzbot+e54f930ed78eb0f85281@syzkaller.appspotmail.com
Signed-off-by: Coleman Dietsch <dietschc@csp.edu>
---
arch/x86/kvm/xen.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 610beba35907..2dd0f72a62f2 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -713,7 +713,10 @@ int kvm_xen_vcpu_set_attr(struct kvm_vcpu *vcpu, struct kvm_xen_vcpu_attr *data)
break;
}
vcpu->arch.xen.timer_virq = data->u.timer.port;
- kvm_xen_init_timer(vcpu);
+
+ /* Check for existing timer */
+ if (!vcpu->arch.xen.timer.function)
+ kvm_xen_init_timer(vcpu);

/* Restart the timer if it's set */
if (data->u.timer.expires_ns)
--
2.34.1
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