On Mon, 22 Feb 2021 16:02:51 +0100 Oleksij Rempel wrote:
> Since 20dd3850bcf8 ("can: Speed up CAN frame receiption by using
> ml_priv") the CAN framework uses per device specific data in the AF_CAN
> protocol. For this purpose the struct net_device->ml_priv is used. Later
> the ml_priv usage in CAN was extended for other users, one of them being
> CAN_J1939.
>
> Later in the kernel ml_priv was converted to an union, used by other
> drivers. E.g. the tun driver started storing it's stats pointer.
>
> Since tun devices can claim to be a CAN device, CAN specific protocols
> will wrongly interpret this pointer, which will cause system crashes.
> Mostly this issue is visible in the CAN_J1939 stack.
>
> To fix this issue, we request a dedicated CAN pointer within the
> net_device struct.
>
> Reported-by: syzbot+5138c4dd15a0401bec7b@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 20dd3850bcf8 ("can: Speed up CAN frame receiption by using ml_priv")
> Fixes: ffd956eef69b ("can: introduce CAN midlayer private and allocate it automatically")
> Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
> Fixes: 497a5757ce4e ("tun: switch to net core provided statistics counters")
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index ddf4cfc12615..6e25c6f0f190 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1584,6 +1584,16 @@ enum netdev_priv_flags {
> #define IFF_L3MDEV_RX_HANDLER IFF_L3MDEV_RX_HANDLER
> #define IFF_LIVE_RENAME_OK IFF_LIVE_RENAME_OK
>
> +/**
> + * enum netdev_ml_priv_type - &struct net_device ml_priv_type
> + *
> + * This enum specifies the type of the struct net_device::ml_priv pointer.
> + */
kdoc (scripts/kernel-doc -none include/linux/netdevice.h) is not happy
about the fact enum values are not defined. Perhaps they will be
sufficiently self-explanatory to not bother documenting?
Maybe just:
/* Specifies the type of the struct net_device::ml_priv pointer */
?
> +enum netdev_ml_priv_type {
> + ML_PRIV_NONE,
> + ML_PRIV_CAN,
> +};
> +
> /**
> * struct net_device - The DEVICE structure.
> *
> @@ -1779,6 +1789,7 @@ enum netdev_priv_flags {
> * @nd_net: Network namespace this network device is inside
> *
> * @ml_priv: Mid-layer private
> + @ml_priv_type: Mid-layer private type
missing '*' at the start of the line
> * @lstats: Loopback statistics
> * @tstats: Tunnel statistics
> * @dstats: Dummy statistics
> @@ -2094,8 +2105,10 @@ struct net_device {
> possible_net_t nd_net;
>
> /* mid-layer private */
> + void *ml_priv;
> + enum netdev_ml_priv_type ml_priv_type;
> +
> union {
> - void *ml_priv;
> struct pcpu_lstats __percpu *lstats;
> struct pcpu_sw_netstats __percpu *tstats;
> struct pcpu_dstats __percpu *dstats;
> @@ -2286,6 +2299,29 @@ static inline void netdev_reset_rx_headroom(struct net_device *dev)
> netdev_set_rx_headroom(dev, -1);
> }
>
> +static inline void *netdev_get_ml_priv(struct net_device *dev,
> + enum netdev_ml_priv_type type)
> +{
> + if (dev->ml_priv_type != type)
> + return NULL;
> +
> + return dev->ml_priv;
> +}
> +
> +static inline void netdev_set_ml_priv(struct net_device *dev,
> + void *ml_priv,
> + enum netdev_ml_priv_type type)
> +{
> + WARN_ONCE(dev->ml_priv_type && dev->ml_priv_type != type,
> + "Overwriting already set ml_priv_type (%u) with different ml_priv_type (%u)!\n",
> + dev->ml_priv_type, type);
> + WARN_ONCE(!dev->ml_priv_type && dev->ml_priv,
> + "Overwriting already set ml_priv and ml_priv_type is ML_PRIV_NONE!\n");
nit: do we need the _ONCE() this helper should be used on control path
and relatively rarely, no?
> + dev->ml_priv = ml_priv;
> + dev->ml_priv_type = type;
> +}
> +
> /*
> * Net namespace inlines
> */
> @@ -454,6 +455,7 @@ static int j1939_sk_bind(struct socket *sock, struct sockaddr *uaddr, int len)
> j1939_local_ecu_put(priv, jsk->addr.src_name, jsk->addr.sa);
> } else {
> struct net_device *ndev;
> + struct can_ml_priv *can_ml;
nit: rev xmas tree
>
> ndev = dev_get_by_index(net, addr->can_ifindex);
> if (!ndev) {
