From 4ea9439fd537313f3381f0af4ebbf05e3f51a58c Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw@amazon.co.uk>
Date: Sat, 12 Nov 2022 13:48:58 +0000
Subject: KVM: x86/xen: Validate port number in SCHEDOP_poll
We shouldn't allow guests to poll on arbitrary port numbers off the end
of the event channel table.
Fixes: 1a65105a5aba ("KVM: x86/xen: handle PV spinlocks slowpath")
[dwmw2: my bug though; the original version did check the validity as a
side-effect of an idr_find() which I ripped out in refactoring.]
Reported-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Cc: stable@kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/xen.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
(limited to 'arch/x86/kvm')
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 2dae413bd62a..dc2f304f2e69 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -954,6 +954,14 @@ static int kvm_xen_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
return kvm_xen_hypercall_set_result(vcpu, run->xen.u.hcall.result);
}
+static inline int max_evtchn_port(struct kvm *kvm)
+{
+ if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode)
+ return EVTCHN_2L_NR_CHANNELS;
+ else
+ return COMPAT_EVTCHN_2L_NR_CHANNELS;
+}
+
static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports,
evtchn_port_t *ports)
{
@@ -1042,6 +1050,10 @@ static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
*r = -EFAULT;
goto out;
}
+ if (ports[i] >= max_evtchn_port(vcpu->kvm)) {
+ *r = -EINVAL;
+ goto out;
+ }
}
if (sched_poll.nr_ports == 1)
@@ -1297,14 +1309,6 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
return 0;
}
-static inline int max_evtchn_port(struct kvm *kvm)
-{
- if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode)
- return EVTCHN_2L_NR_CHANNELS;
- else
- return COMPAT_EVTCHN_2L_NR_CHANNELS;
-}
-
static void kvm_xen_check_poller(struct kvm_vcpu *vcpu, int port)
{
int poll_evtchn = vcpu->arch.xen.poll_evtchn;
--
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