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net: rmnet: no longer rely on RTNL in rmnet_fill_info()

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rmnet_fill_info() used rmnet_get_port_rtnl(), and thus required
RTNL.

Now that priv->mux_id and port->data_format are properly
annotated, rmnet_fill_info() can simply fetch the port under
rcu_read_lock().

rmnet_get_port_rcu() was only used from the data path and thus
used rcu_dereference_bh(). Relax its lockdep condition so that it
can also be called from process context under a plain
rcu_read_lock(), and use it from rmnet_fill_info().

Note that rmnet_get_port_rcu() checks real_dev->rx_handler before
returning rx_handler_data: this is what makes the lockless lookup
safe against rmnet_unregister_real_device(), which clears
rx_handler, waits for a grace period in
netdev_rx_handler_unregister(), and only then frees the port.

While at it, add missing const qualifiers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Sean Tranchetti <sean.tranchetti@oss.qualcomm.com>
Reviewed-by: Subash Abhinov Kasiviswanathan <subash.a.kasiviswanathan@oss.qualcomm.com>
Link: https://patch.msgid.link/20260916132231.1780091-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2026-09-16 13:22:31 +00:00 committed by Jakub Kicinski
parent 0067187dbe
commit d7c9ba103b
2 changed files with 18 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c
View File

@ -377,32 +377,24 @@ static size_t rmnet_get_size(const struct net_device *dev)
static int rmnet_fill_info(struct sk_buff *skb, const struct net_device *dev)
{
struct rmnet_priv *priv = netdev_priv(dev);
struct net_device *real_dev;
const struct rmnet_priv *priv = netdev_priv(dev);
const struct rmnet_port *port;
struct ifla_rmnet_flags f;
struct rmnet_port *port;
real_dev = priv->real_dev;
if (nla_put_u16(skb, IFLA_RMNET_MUX_ID, READ_ONCE(priv->mux_id)))
return -EMSGSIZE;
if (nla_put_u16(skb, IFLA_RMNET_MUX_ID, priv->mux_id))
goto nla_put_failure;
if (rmnet_is_real_dev_registered(real_dev)) {
port = rmnet_get_port_rtnl(real_dev);
f.flags = port->data_format;
} else {
f.flags = 0;
}
rcu_read_lock();
port = rmnet_get_port_rcu(priv->real_dev);
f.flags = port ? READ_ONCE(port->data_format) : 0;
rcu_read_unlock();
f.mask = ~0;
if (nla_put(skb, IFLA_RMNET_FLAGS, sizeof(f), &f))
goto nla_put_failure;
return -EMSGSIZE;
return 0;
nla_put_failure:
return -EMSGSIZE;
}
struct rtnl_link_ops rmnet_link_ops __read_mostly = {
@ -419,12 +411,16 @@ struct rtnl_link_ops rmnet_link_ops __read_mostly = {
.fill_info = rmnet_fill_info,
};
struct rmnet_port *rmnet_get_port_rcu(struct net_device *real_dev)
/* Can be called from a RCU read-side critical section, with or
* without BH disabled.
*/
struct rmnet_port *rmnet_get_port_rcu(const struct net_device *real_dev)
{
if (rmnet_is_real_dev_registered(real_dev))
return rcu_dereference_bh(real_dev->rx_handler_data);
else
if (!rmnet_is_real_dev_registered(real_dev))
return NULL;
return rcu_dereference_check(real_dev->rx_handler_data,
rcu_read_lock_bh_held());
}
struct rmnet_endpoint *rmnet_get_endpoint(struct rmnet_port *port, u8 mux_id)

2
drivers/net/ethernet/qualcomm/rmnet/rmnet_config.h
View File

@ -90,7 +90,7 @@ struct rmnet_priv {
struct rmnet_priv_stats stats;
};
struct rmnet_port *rmnet_get_port_rcu(struct net_device *real_dev);
struct rmnet_port *rmnet_get_port_rcu(const struct net_device *real_dev);
struct rmnet_endpoint *rmnet_get_endpoint(struct rmnet_port *port, u8 mux_id);
int rmnet_add_bridge(struct net_device *rmnet_dev,
struct net_device *slave_dev,