From: David Woodhouse <dwmw@xxxxxxxxxxxx>
In particular, we shouldn't assume that being contiguous in guest virtual
address space means being contiguous in guest *physical* address space.
In dropping the manual calls to kvm_mmu_gva_to_gpa_system(), also drop
the srcu_read_lock() that was around them. All call sites are reached
from kvm_xen_hypercall() which is called from the handle_exit function
with the read lock already held.
Fixes: 2fd6df2f2 ("KVM: x86/xen: intercept EVTCHNOP_send from guests")
536395260 ("KVM: x86/xen: handle PV timers oneshot mode")
1a65105a5 ("KVM: x86/xen: handle PV spinlocks slowpath")
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
Spotted the same issue in the QEMU patches while working through them:
https://git.infradead.org/users/dwmw2/qemu.git/shortlog/refs/heads/xenfv
Then realised it was like that in the kernel too.
arch/x86/kvm/xen.c | 56 +++++++++++++++-------------------------------
1 file changed, 18 insertions(+), 38 deletions(-)
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index d7af40240248..5be1090b2317 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -1183,30 +1183,22 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports,
static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
u64 param, u64 *r)
{
- int idx, i;
struct sched_poll sched_poll;
evtchn_port_t port, *ports;
- gpa_t gpa;
+ struct x86_exception e;
+ int i;
if (!lapic_in_kernel(vcpu) ||
!(vcpu->kvm->arch.xen_hvm_config.flags & KVM_XEN_HVM_CONFIG_EVTCHN_SEND))
return false;
- idx = srcu_read_lock(&vcpu->kvm->srcu);
- gpa = kvm_mmu_gva_to_gpa_system(vcpu, param, NULL);
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
- if (!gpa) {
- *r = -EFAULT;
- return true;
- }
-
if (IS_ENABLED(CONFIG_64BIT) && !longmode) {
struct compat_sched_poll sp32;
/* Sanity check that the compat struct definition is correct */
BUILD_BUG_ON(sizeof(sp32) != 16);
- if (kvm_vcpu_read_guest(vcpu, gpa, &sp32, sizeof(sp32))) {
+ if (kvm_read_guest_virt(vcpu, param, &sp32, sizeof(sp32), &e)) {
*r = -EFAULT;
return true;
}
@@ -1220,8 +1212,8 @@ static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
sched_poll.nr_ports = sp32.nr_ports;
sched_poll.timeout = sp32.timeout;
} else {
- if (kvm_vcpu_read_guest(vcpu, gpa, &sched_poll,
- sizeof(sched_poll))) {
+ if (kvm_read_guest_virt(vcpu, param, &sched_poll,
+ sizeof(sched_poll), &e)) {
*r = -EFAULT;
return true;
}
@@ -1243,18 +1235,13 @@ static bool kvm_xen_schedop_poll(struct kvm_vcpu *vcpu, bool longmode,
} else
ports = &port;
+ if (kvm_read_guest_virt(vcpu, (gva_t)sched_poll.ports, ports,
+ sched_poll.nr_ports * sizeof(*ports), &e)) {
+ *r = -EFAULT;
+ return true;
+ }
+
for (i = 0; i < sched_poll.nr_ports; i++) {
- idx = srcu_read_lock(&vcpu->kvm->srcu);
- gpa = kvm_mmu_gva_to_gpa_system(vcpu,
- (gva_t)(sched_poll.ports + i),
- NULL);
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
-
- if (!gpa || kvm_vcpu_read_guest(vcpu, gpa,
- &ports[i], sizeof(port))) {
- *r = -EFAULT;
- goto out;
- }
if (ports[i] >= max_evtchn_port(vcpu->kvm)) {
*r = -EINVAL;
goto out;
@@ -1330,9 +1317,8 @@ static bool kvm_xen_hcall_vcpu_op(struct kvm_vcpu *vcpu, bool longmode, int cmd,
int vcpu_id, u64 param, u64 *r)
{
struct vcpu_set_singleshot_timer oneshot;
+ struct x86_exception e;
s64 delta;
- gpa_t gpa;
- int idx;
if (!kvm_xen_timer_enabled(vcpu))
return false;
@@ -1343,9 +1329,6 @@ static bool kvm_xen_hcall_vcpu_op(struct kvm_vcpu *vcpu, bool longmode, int cmd,
*r = -EINVAL;
return true;
}
- idx = srcu_read_lock(&vcpu->kvm->srcu);
- gpa = kvm_mmu_gva_to_gpa_system(vcpu, param, NULL);
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
/*
* The only difference for 32-bit compat is the 4 bytes of
@@ -1363,9 +1346,8 @@ static bool kvm_xen_hcall_vcpu_op(struct kvm_vcpu *vcpu, bool longmode, int cmd,
BUILD_BUG_ON(sizeof_field(struct compat_vcpu_set_singleshot_timer, flags) !=
sizeof_field(struct vcpu_set_singleshot_timer, flags));
- if (!gpa ||
- kvm_vcpu_read_guest(vcpu, gpa, &oneshot, longmode ? sizeof(oneshot) :
- sizeof(struct compat_vcpu_set_singleshot_timer))) {
+ if (kvm_read_guest_virt(vcpu, param, &oneshot, longmode ? sizeof(oneshot) :
+ sizeof(struct compat_vcpu_set_singleshot_timer), &e)) {
*r = -EFAULT;
return true;
}
@@ -2002,14 +1984,12 @@ static bool kvm_xen_hcall_evtchn_send(struct kvm_vcpu *vcpu, u64 param, u64 *r)
{
struct evtchnfd *evtchnfd;
struct evtchn_send send;
- gpa_t gpa;
- int idx;
+ struct x86_exception e;
- idx = srcu_read_lock(&vcpu->kvm->srcu);
- gpa = kvm_mmu_gva_to_gpa_system(vcpu, param, NULL);
- srcu_read_unlock(&vcpu->kvm->srcu, idx);
+ /* Sanity check: this structure is the same for 32-bit and 64-bit */
+ BUILD_BUG_ON(sizeof(send) != 4);
- if (!gpa || kvm_vcpu_read_guest(vcpu, gpa, &send, sizeof(send))) {
+ if (kvm_read_guest_virt(vcpu, param, &send, sizeof(send), &e)) {
*r = -EFAULT;
return true;
}
--
2.25.1
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