Subject: Re: [PATCH] RDMA/siw: Remove direct link to net_device

From: Zhu Yanjun <[email-masked]>
Date: Tue, 10 Dec 2024 16:44:40 +0100

On 10.12.24 14:03, Bernard Metzler wrote:
> Maintain needed network interface information locally, but
> remove a direct link to net_device which can become stale.
> Accessing a stale net_device link was causing a 'KASAN:
> slab-use-after-free' exception during siw_query_port()
> call.
> 
> Fixes: bdcf26bf9b3a ("rdma/siw: network and RDMA core interface")
> Reported-by: [email-masked]
> Link: https://syzkaller.appspot.com/bug?extid=4b87489410b4efd181bf
> Signed-off-by: Bernard Metzler <[email-masked]>
> ---
>   drivers/infiniband/sw/siw/siw.h       | 11 +++++++----
>   drivers/infiniband/sw/siw/siw_cm.c    |  4 ++--
>   drivers/infiniband/sw/siw/siw_main.c  | 18 ++++++++++++------
>   drivers/infiniband/sw/siw/siw_verbs.c | 11 ++++++-----
>   4 files changed, 27 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/siw/siw.h b/drivers/infiniband/sw/siw/siw.h
> index 86d4d6a2170e..c8f75527b513 100644
> --- a/drivers/infiniband/sw/siw/siw.h
> +++ b/drivers/infiniband/sw/siw/siw.h
> @@ -69,16 +69,19 @@ struct siw_pd {
>   
>   struct siw_device {
>   	struct ib_device base_dev;
> -	struct net_device *netdev;
>   	struct siw_dev_cap attrs;
>   
>   	u32 vendor_part_id;
> +	struct {
> +		int ifindex;
> +		enum ib_port_state state;
> +		enum ib_mtu mtu;
> +		enum ib_mtu max_mtu;
> +	} ifinfo;
> +
>   	int numa_node;
>   	char raw_gid[ETH_ALEN];
>   
> -	/* physical port state (only one port per device) */
> -	enum ib_port_state state;
> -
>   	spinlock_t lock;
>   
>   	struct xarray qp_xa;
> diff --git a/drivers/infiniband/sw/siw/siw_cm.c b/drivers/infiniband/sw/siw/siw_cm.c
> index 86323918a570..451b50d92f7f 100644
> --- a/drivers/infiniband/sw/siw/siw_cm.c
> +++ b/drivers/infiniband/sw/siw/siw_cm.c
> @@ -1780,7 +1780,7 @@ int siw_create_listen(struct iw_cm_id *id, int backlog)
>   
>   		/* For wildcard addr, limit binding to current device only */
>   		if (ipv4_is_zeronet(laddr->sin_addr.s_addr))
> -			s->sk->sk_bound_dev_if = sdev->netdev->ifindex;
> +			s->sk->sk_bound_dev_if = sdev->ifinfo.ifindex;
>   
>   		rv = s->ops->bind(s, (struct sockaddr *)laddr,
>   				  sizeof(struct sockaddr_in));
> @@ -1798,7 +1798,7 @@ int siw_create_listen(struct iw_cm_id *id, int backlog)
>   
>   		/* For wildcard addr, limit binding to current device only */
>   		if (ipv6_addr_any(&laddr->sin6_addr))
> -			s->sk->sk_bound_dev_if = sdev->netdev->ifindex;
> +			s->sk->sk_bound_dev_if = sdev->ifinfo.ifindex;
>   
>   		rv = s->ops->bind(s, (struct sockaddr *)laddr,
>   				  sizeof(struct sockaddr_in6));
> diff --git a/drivers/infiniband/sw/siw/siw_main.c b/drivers/infiniband/sw/siw/siw_main.c
> index 17abef48abcd..4db10bdfb515 100644
> --- a/drivers/infiniband/sw/siw/siw_main.c
> +++ b/drivers/infiniband/sw/siw/siw_main.c
> @@ -287,7 +287,6 @@ static struct siw_device *siw_device_create(struct net_device *netdev)
>   		return NULL;
>   
>   	base_dev = &sdev->base_dev;
> -	sdev->netdev = netdev;
>   
>   	if (netdev->addr_len) {
>   		memcpy(sdev->raw_gid, netdev->dev_addr,
> @@ -354,6 +353,10 @@ static struct siw_device *siw_device_create(struct net_device *netdev)
>   	atomic_set(&sdev->num_mr, 0);
>   	atomic_set(&sdev->num_pd, 0);
>   
> +	sdev->ifinfo.max_mtu = ib_mtu_int_to_enum(netdev->max_mtu);
> +	sdev->ifinfo.mtu = ib_mtu_int_to_enum(READ_ONCE(netdev->mtu));
> +	sdev->ifinfo.ifindex = netdev->ifindex;
> +
>   	sdev->numa_node = dev_to_node(&netdev->dev);
>   	spin_lock_init(&sdev->lock);
>   
> @@ -381,12 +384,12 @@ static int siw_netdev_event(struct notifier_block *nb, unsigned long event,
>   
>   	switch (event) {
>   	case NETDEV_UP:
> -		sdev->state = IB_PORT_ACTIVE;
> +		sdev->ifinfo.state = IB_PORT_ACTIVE;
>   		siw_port_event(sdev, 1, IB_EVENT_PORT_ACTIVE);
>   		break;
>   
>   	case NETDEV_DOWN:
> -		sdev->state = IB_PORT_DOWN;
> +		sdev->ifinfo.state = IB_PORT_DOWN;
>   		siw_port_event(sdev, 1, IB_EVENT_PORT_ERR);
>   		break;
>   
> @@ -406,10 +409,13 @@ static int siw_netdev_event(struct notifier_block *nb, unsigned long event,
>   	case NETDEV_CHANGEADDR:
>   		siw_port_event(sdev, 1, IB_EVENT_LID_CHANGE);
>   		break;
> +
> +	case NETDEV_CHANGEMTU:
> +		sdev->ifinfo.mtu = ib_mtu_int_to_enum(READ_ONCE(netdev->mtu));
> +		break;
>   	/*
>   	 * Todo: Below netdev events are currently not handled.
>   	 */
> -	case NETDEV_CHANGEMTU:
>   	case NETDEV_CHANGE:
>   		break;
>   
> @@ -444,9 +450,9 @@ static int siw_newlink(const char *basedev_name, struct net_device *netdev)
>   		dev_dbg(&netdev->dev, "siw: new device\n");
>   
>   		if (netif_running(netdev) && netif_carrier_ok(netdev))
> -			sdev->state = IB_PORT_ACTIVE;
> +			sdev->ifinfo.state = IB_PORT_ACTIVE;
>   		else
> -			sdev->state = IB_PORT_DOWN;
> +			sdev->ifinfo.state = IB_PORT_DOWN;
>   
>   		ib_mark_name_assigned_by_user(&sdev->base_dev);
>   		rv = siw_device_register(sdev, basedev_name);
> diff --git a/drivers/infiniband/sw/siw/siw_verbs.c b/drivers/infiniband/sw/siw/siw_verbs.c
> index 986666c19378..3ab9c5170637 100644
> --- a/drivers/infiniband/sw/siw/siw_verbs.c
> +++ b/drivers/infiniband/sw/siw/siw_verbs.c
> @@ -178,14 +178,15 @@ int siw_query_port(struct ib_device *base_dev, u32 port,
>   
>   	rv = ib_get_eth_speed(base_dev, port, &attr->active_speed,
>   			 &attr->active_width);
> +
>   	attr->gid_tbl_len = 1;
>   	attr->max_msg_sz = -1;
> -	attr->max_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
> -	attr->active_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
> -	attr->phys_state = sdev->state == IB_PORT_ACTIVE ?
> +	attr->max_mtu = sdev->ifinfo.max_mtu;
> +	attr->active_mtu = sdev->ifinfo.mtu;
> +	attr->phys_state = sdev->ifinfo.state == IB_PORT_ACTIVE ?
>   		IB_PORT_PHYS_STATE_LINK_UP : IB_PORT_PHYS_STATE_DISABLED;
>   	attr->port_cap_flags = IB_PORT_CM_SUP | IB_PORT_DEVICE_MGMT_SUP;
> -	attr->state = sdev->state;
> +	attr->state = sdev->ifinfo.state;
>   	/*
>   	 * All zero
>   	 *
> @@ -519,7 +520,7 @@ int siw_query_qp(struct ib_qp *base_qp, struct ib_qp_attr *qp_attr,
>   	qp_attr->cap.max_send_sge = qp->attrs.sq_max_sges;
>   	qp_attr->cap.max_recv_wr = qp->attrs.rq_size;
>   	qp_attr->cap.max_recv_sge = qp->attrs.rq_max_sges;
> -	qp_attr->path_mtu = ib_mtu_int_to_enum(sdev->netdev->mtu);
> +	qp_attr->path_mtu = sdev->ifinfo.mtu;

The followings are my fix to this kind of problem 
https://syzkaller.appspot.com/bug?extid=4b87489410b4efd181bf

It seems that it can also fix this problem.
After I delved into your commit, I wonder what happen if the netdev will 
be handled in the future after xxx_query_port?

Thanks,

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c 
b/drivers/infiniband/sw/rxe/rxe_verbs.c
index 5c18f7e342f2..7c73eb9115f1 100644
--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -57,7 +57,7 @@ static int rxe_query_port(struct ib_device *ibdev,

         if (attr->state == IB_PORT_ACTIVE)
                 attr->phys_state = IB_PORT_PHYS_STATE_LINK_UP;
-       else if (dev_get_flags(rxe->ndev) & IFF_UP)
+       else if (rxe && rxe->ndev && (dev_get_flags(rxe->ndev) & IFF_UP))
                 attr->phys_state = IB_PORT_PHYS_STATE_POLLING;
         else
                 attr->phys_state = IB_PORT_PHYS_STATE_DISABLED;

Zhu Yanjun

>   	qp_attr->max_rd_atomic = qp->attrs.irq_size;
>   	qp_attr->max_dest_rd_atomic = qp->attrs.orq_size;
>