Hi,
On Sun, Sep 26, 2021 at 06:47:57PM +0800, Ziyang Xuan wrote:
> 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.
>
> Fixes: 9d71dd0c70099 ("can: add support of SAE J1939 protocol")
> Reported-by: syzbot+85d9878b19c94f9019ad@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
Thank you!
Acked-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
> net/can/j1939/main.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
> index 08c8606cfd9c..9bc55ecb37f9 100644
> --- a/net/can/j1939/main.c
> +++ b/net/can/j1939/main.c
> @@ -249,11 +249,14 @@ struct j1939_priv *j1939_netdev_start(struct net_device *ndev)
> struct j1939_priv *priv, *priv_new;
> int ret;
>
> - priv = j1939_priv_get_by_ndev(ndev);
> + spin_lock(&j1939_netdev_lock);
> + priv = j1939_priv_get_by_ndev_locked(ndev);
> if (priv) {
> kref_get(&priv->rx_kref);
> + spin_unlock(&j1939_netdev_lock);
> return priv;
> }
> + spin_unlock(&j1939_netdev_lock);
>
> priv = j1939_priv_create(ndev);
> if (!priv)
> @@ -269,10 +272,10 @@ struct j1939_priv *j1939_netdev_start(struct net_device *ndev)
> /* Someone was faster than us, use their priv and roll
> * back our's.
> */
> + kref_get(&priv_new->rx_kref);
> spin_unlock(&j1939_netdev_lock);
> dev_put(ndev);
> kfree(priv);
> - kref_get(&priv_new->rx_kref);
> return priv_new;
> }
> j1939_priv_set(ndev, priv);
> --
> 2.25.1
>
>
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