From 8f44631ba02afe9fff2f0a0fb66560ab19df87fd Mon Sep 17 00:00:00 2001 From: Xiao Liang Date: Tue, 27 Oct 2026 18:18:27 +0800 Subject: [PATCH] tun: drop batched packets while the device is down tun_sendmsg() handles TUN_MSG_PTR batches from vhost-net by calling tun_xdp_one() instead of tun_get_user(). But this path does not check IFF_UP, allowing packets from a guest to be injected into the host receive path while the device is administratively down. Check IFF_UP in tun_xdp_one() before running XDP or building an skb. Drop the packet when the device is down, matching tun_get_user(). Fixes: 043d222f93ab ("tuntap: accept an array of XDP buffs through sendmsg()") Signed-off-by: Xiao Liang Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20261027101830.85327-1-shaw.leon@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/tun.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 770b8fe085c3..dcec7311e601 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -2555,6 +2555,12 @@ static int tun_xdp_one(struct tun_struct *tun, return -EINVAL; } + if (unlikely(!(READ_ONCE(tun->dev->flags) & IFF_UP))) { + put_page(virt_to_head_page(xdp->data)); + dev_core_stats_rx_dropped_inc(tun->dev); + return -EIO; + } + xdp_prog = rcu_dereference(tun->xdp_prog); if (xdp_prog) { if (gso->gso_type) {