net: check for driver support in netmem TX

We should not enable netmem TX for drivers that don't declare support.

Check for driver netmem TX support during devmem TX binding and fail if
the driver does not have the functionality.

Check for driver support in validate_xmit_skb as well.

Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508004830.4100853-9-almasrymina@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/core/dev.c b/net/core/dev.c
index c901363..33d5e95 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3896,12 +3896,42 @@ sw_checksum:
 }
 EXPORT_SYMBOL(skb_csum_hwoffload_help);
 
+static struct sk_buff *validate_xmit_unreadable_skb(struct sk_buff *skb,
+                                                   struct net_device *dev)
+{
+       struct skb_shared_info *shinfo;
+       struct net_iov *niov;
+
+       if (likely(skb_frags_readable(skb)))
+               goto out;
+
+       if (!dev->netmem_tx)
+               goto out_free;
+
+       shinfo = skb_shinfo(skb);
+
+       if (shinfo->nr_frags > 0) {
+               niov = netmem_to_net_iov(skb_frag_netmem(&shinfo->frags[0]));
+               if (net_is_devmem_iov(niov) &&
+                   net_devmem_iov_binding(niov)->dev != dev)
+                       goto out_free;
+       }
+
+out:
+       return skb;
+
+out_free:
+       kfree_skb(skb);
+       return NULL;
+}
+
 static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device *dev, bool *again)
 {
        netdev_features_t features;
 
-       if (!skb_frags_readable(skb))
-               goto out_kfree_skb;
+       skb = validate_xmit_unreadable_skb(skb, dev);
+       if (unlikely(!skb))
+               goto out_null;
 
        features = netif_skb_features(skb);
        skb = validate_xmit_vlan(skb, features);

diff --git a/net/core/devmem.h b/net/core/devmem.h
index 67168aa..919e6ed 100644 (file)
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -229,6 +229,12 @@ net_devmem_get_niov_at(struct net_devmem_dmabuf_binding *binding, size_t addr,
 {
        return NULL;
 }
+
+static inline struct net_devmem_dmabuf_binding *
+net_devmem_iov_binding(const struct net_iov *niov)
+{
+       return NULL;
+}
 #endif
 
 #endif /* _NET_DEVMEM_H */

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 93ea57d..cfcf165 100644 (file)
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -1013,6 +1013,13 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
                goto err_unlock_netdev;
        }
 
+       if (!netdev->netmem_tx) {
+               err = -EOPNOTSUPP;
+               NL_SET_ERR_MSG(info->extack,
+                              "Driver does not support netmem TX");
+               goto err_unlock_netdev;
+       }
+
        binding = net_devmem_bind_dmabuf(netdev, DMA_TO_DEVICE, dmabuf_fd,
                                         info->extack);
        if (IS_ERR(binding)) {