On 10/28/22 11:26, Eiichi Tsukata wrote:
Should not call eventfd_ctx_put() in case of error.
Fixes: 2fd6df2f2b47 ("KVM: x86/xen: intercept EVTCHNOP_send from guests")
Reported-by: syzbot+6f0c896c5a9449a10ded@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Eiichi Tsukata <eiichi.tsukata@xxxxxxxxxxx>
---
arch/x86/kvm/xen.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 93c628d3e3a9..a357994982c6 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1716,7 +1716,7 @@ static int kvm_xen_eventfd_assign(struct kvm *kvm,
if (ret == -ENOSPC)
ret = -EEXIST;
out:
- if (eventfd)
+ if (eventfd && !IS_ERR(eventfd))
eventfd_ctx_put(eventfd);
kfree(evtchnfd);
return ret;
Slightly more verbose, but cleaner:
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 6714bbdbedf3..2dae413bd62a 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1666,18 +1666,18 @@ static int kvm_xen_eventfd_assign(struct kvm *kvm,
case EVTCHNSTAT_ipi:
/* IPI must map back to the same port# */
if (data->u.evtchn.deliver.port.port != data->u.evtchn.send_port)
- goto out; /* -EINVAL */
+ goto out_noeventfd; /* -EINVAL */
break;
case EVTCHNSTAT_interdomain:
if (data->u.evtchn.deliver.port.port) {
if (data->u.evtchn.deliver.port.port >= max_evtchn_port(kvm))
- goto out; /* -EINVAL */
+ goto out_noeventfd; /* -EINVAL */
} else {
eventfd = eventfd_ctx_fdget(data->u.evtchn.deliver.eventfd.fd);
if (IS_ERR(eventfd)) {
ret = PTR_ERR(eventfd);
- goto out;
+ goto out_noeventfd;
}
}
break;
@@ -1717,6 +1717,7 @@ static int kvm_xen_eventfd_assign(struct kvm *kvm,
out:
if (eventfd)
eventfd_ctx_put(eventfd);
+out_noeventfd:
kfree(evtchnfd);
return ret;
}
Only the last goto has to be changed in order to fix the bug, the
others are only needed to respect the LIFO order of the unwinding
labels.
Paolo
