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authorPaolo Bonzini <pbonzini@redhat.com>2022-11-23 18:52:29 -0500
committerPaolo Bonzini <pbonzini@redhat.com>2022-11-23 18:59:45 -0500
commitfe08e36be9ecbf6b38714a77c97b1d25b7a6e4b0 (patch)
tree9ad343989dfe2029c80f8e4f86c828504edba428
parent47b0c2e4c220f2251fd8dcfbb44479819c715e15 (diff)
parent8332f0ed4f187c7b700831bd7cc83ce180a944b9 (diff)
Merge branch 'kvm-dwmw2-fixes' into HEAD
This brings in a few important fixes for Xen emulation. While nobody should be enabling it, the bug effectively allows userspace to read arbitrary memory. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kvm/xen.c32
-rw-r--r--virt/kvm/pfncache.c7
2 files changed, 29 insertions, 10 deletions
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 2dae413bd62a..f3098c0e386a 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)
@@ -1215,6 +1227,7 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
bool longmode;
u64 input, params[6], r = -ENOSYS;
bool handled = false;
+ u8 cpl;
input = (u64)kvm_register_read(vcpu, VCPU_REGS_RAX);
@@ -1242,9 +1255,17 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
params[5] = (u64)kvm_r9_read(vcpu);
}
#endif
+ cpl = static_call(kvm_x86_get_cpl)(vcpu);
trace_kvm_xen_hypercall(input, params[0], params[1], params[2],
params[3], params[4], params[5]);
+ /*
+ * Only allow hypercall acceleration for CPL0. The rare hypercalls that
+ * are permitted in guest userspace can be handled by the VMM.
+ */
+ if (unlikely(cpl > 0))
+ goto handle_in_userspace;
+
switch (input) {
case __HYPERVISOR_xen_version:
if (params[0] == XENVER_version && vcpu->kvm->arch.xen.xen_version) {
@@ -1279,10 +1300,11 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu)
if (handled)
return kvm_xen_hypercall_set_result(vcpu, r);
+handle_in_userspace:
vcpu->run->exit_reason = KVM_EXIT_XEN;
vcpu->run->xen.type = KVM_EXIT_XEN_HCALL;
vcpu->run->xen.u.hcall.longmode = longmode;
- vcpu->run->xen.u.hcall.cpl = static_call(kvm_x86_get_cpl)(vcpu);
+ vcpu->run->xen.u.hcall.cpl = cpl;
vcpu->run->xen.u.hcall.input = input;
vcpu->run->xen.u.hcall.params[0] = params[0];
vcpu->run->xen.u.hcall.params[1] = params[1];
@@ -1297,14 +1319,6 @@ 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;
diff --git a/virt/kvm/pfncache.c b/virt/kvm/pfncache.c
index 346e47f15572..7c248193ca26 100644
--- a/virt/kvm/pfncache.c
+++ b/virt/kvm/pfncache.c
@@ -297,7 +297,12 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,
if (!gpc->valid || old_uhva != gpc->uhva) {
ret = hva_to_pfn_retry(kvm, gpc);
} else {
- /* If the HVA→PFN mapping was already valid, don't unmap it. */
+ /*
+ * If the HVA→PFN mapping was already valid, don't unmap it.
+ * But do update gpc->khva because the offset within the page
+ * may have changed.
+ */
+ gpc->khva = old_khva + page_offset;
old_pfn = KVM_PFN_ERR_FAULT;
old_khva = NULL;
ret = 0;