Wrap the vcpu->pid dereference in the debugfs hook vcpu_get_pid() with
proper RCU read (un)lock. Unlike the code in kvm_vcpu_ioctl(),
vcpu_get_pid() is not a simple access; the pid pointer is passed to
pid_nr() and fully dereferenced if the pointer is non-NULL.
Failure to acquire RCU could result in use-after-free of the old pid if
a different task invokes KVM_RUN and puts the last reference to the old
vcpu->pid between vcpu_get_pid() reading the pointer and dereferencing it
in pid_nr().
Fixes: e36de87d34a7 ("KVM: debugfs: expose pid of vcpu threads")
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
virt/kvm/kvm_main.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d255964ec331..b7b72c8fb492 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3867,7 +3867,10 @@ static int create_vcpu_fd(struct kvm_vcpu *vcpu)
static int vcpu_get_pid(void *data, u64 *val)
{
struct kvm_vcpu *vcpu = (struct kvm_vcpu *) data;
- *val = pid_nr(rcu_access_pointer(vcpu->pid));
+
+ rcu_read_lock();
+ *val = pid_nr(rcu_dereference(vcpu->pid));
+ rcu_read_unlock();
return 0;
}
base-commit: 7cb79f433e75b05d1635aefaa851cfcd1cb7dc4f
--
2.39.1.581.gbfd45094c4-goog
