We do use rcu to protect the pid pointer. Mark it as such and
adopt all code to use the proper access methods.
This was detected by sparse.
"virt/kvm/kvm_main.c:2248:15: error: incompatible types in comparison
expression (different address spaces)"
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 15 +++++++++++----
2 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 0b50e7b..bcd37b8 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -234,7 +234,7 @@ struct kvm_vcpu {
int guest_fpu_loaded, guest_xcr0_loaded;
struct swait_queue_head wq;
- struct pid *pid;
+ struct pid __rcu *pid;
int sigset_active;
sigset_t sigset;
struct kvm_vcpu_stat stat;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 19f0ecb..7bd5509 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -293,7 +293,12 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_init);
void kvm_vcpu_uninit(struct kvm_vcpu *vcpu)
{
- put_pid(vcpu->pid);
+ /*
+ * no need for rcu_read_lock as VCPU_RUN is the only place that
+ * will change the vcpu->pid pointer and on uninit all file
+ * descriptors are already gone.
+ */
+ put_pid(rcu_dereference(vcpu->pid));
kvm_arch_vcpu_uninit(vcpu);
free_page((unsigned long)vcpu->run);
}
@@ -2551,13 +2556,14 @@ static long kvm_vcpu_ioctl(struct file *filp,
if (r)
return r;
switch (ioctl) {
- case KVM_RUN:
+ case KVM_RUN: {
+ struct pid *oldpid;
r = -EINVAL;
if (arg)
goto out;
- if (unlikely(vcpu->pid != current->pids[PIDTYPE_PID].pid)) {
+ oldpid = rcu_dereference(vcpu->pid);
+ if (unlikely(oldpid != current->pids[PIDTYPE_PID].pid)) {
/* The thread running this VCPU changed. */
- struct pid *oldpid = vcpu->pid;
struct pid *newpid = get_task_pid(current, PIDTYPE_PID);
rcu_assign_pointer(vcpu->pid, newpid);
@@ -2568,6 +2574,7 @@ static long kvm_vcpu_ioctl(struct file *filp,
r = kvm_arch_vcpu_ioctl_run(vcpu, vcpu->run);
trace_kvm_userspace_exit(vcpu->run->exit_reason, r);
break;
+ }
case KVM_GET_REGS: {
struct kvm_regs *kvm_regs;
--
2.7.4
