From: Eric Dumazet Date: Wed, 4 Jun 2025 10:58:15 +0000 (+0000) Subject: net: prevent a NULL deref in rtnl_create_link() X-Git-Tag: v6.16-rc1~36^2~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=feafc73f3e6ae73371777a037d41d2e31c929636;p=thirdparty%2Fkernel%2Flinux.git net: prevent a NULL deref in rtnl_create_link() At the time rtnl_create_link() is running, dev->netdev_ops is NULL, we must not use netdev_lock_ops() or risk a NULL deref if CONFIG_NET_SHAPER is defined. Use netif_set_group() instead of dev_set_group(). RIP: 0010:netdev_need_ops_lock include/net/netdev_lock.h:33 [inline] RIP: 0010:netdev_lock_ops include/net/netdev_lock.h:41 [inline] RIP: 0010:dev_set_group+0xc0/0x230 net/core/dev_api.c:82 Call Trace: rtnl_create_link+0x748/0xd10 net/core/rtnetlink.c:3674 rtnl_newlink_create+0x25c/0xb00 net/core/rtnetlink.c:3813 __rtnl_newlink net/core/rtnetlink.c:3940 [inline] rtnl_newlink+0x16d6/0x1c70 net/core/rtnetlink.c:4055 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6944 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:712 [inline] Reported-by: syzbot+9fc858ba0312b42b577e@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6840265f.a00a0220.d4325.0009.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Fixes: 7e4d784f5810 ("net: hold netdev instance lock during rtnetlink operations") Acked-by: Stanislav Fomichev Link: https://patch.msgid.link/20250604105815.1516973-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index f9a35bdc58ad..c57692eb8da9 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -3671,7 +3671,7 @@ struct net_device *rtnl_create_link(struct net *net, const char *ifname, if (tb[IFLA_LINKMODE]) dev->link_mode = nla_get_u8(tb[IFLA_LINKMODE]); if (tb[IFLA_GROUP]) - dev_set_group(dev, nla_get_u32(tb[IFLA_GROUP])); + netif_set_group(dev, nla_get_u32(tb[IFLA_GROUP])); if (tb[IFLA_GSO_MAX_SIZE]) netif_set_gso_max_size(dev, nla_get_u32(tb[IFLA_GSO_MAX_SIZE])); if (tb[IFLA_GSO_MAX_SEGS])