CVE-2021-47459

In the Linux kernel, the following vulnerability has been resolved: can:
j1939: j1939_netdev_start(): fix UAF for rx_kref of j1939_priv It will
trigger UAF for rx_kref of j1939_priv as following. cpu0 cpu1
j1939_sk_bind(socket0, ndev0, …) j1939_netdev_start
j1939_sk_bind(socket1, ndev0, …) j1939_netdev_start j1939_priv_set
j1939_priv_get_by_ndev_locked j1939_jsk_add … j1939_netdev_stop
kref_put_lock(&priv->rx_kref, …) kref_get(&priv->rx_kref, …)
REFCOUNT_WARN(“addition on 0;…”)
==================================================== refcount_t: addition
on 0; use-after-free. WARNING: CPU: 1 PID: 20874 at lib/refcount.c:25
refcount_warn_saturate+0x169/0x1e0 RIP:
0010:refcount_warn_saturate+0x169/0x1e0 Call Trace:
j1939_netdev_start+0x68b/0x920 j1939_sk_bind+0x426/0xeb0 ?
security_socket_bind+0x83/0xb0 The rx_kref’s kref_get() and kref_put()
should use j1939_netdev_lock to protect.