From f4feb1e20058e407cb00f45aff47f5b7e19a6bbf Mon Sep 17 00:00:00 2001 From: Weiming Shi Date: Wed, 20 May 2026 09:00:21 -0700 Subject: [PATCH] tun: free page on short-frame rejection in tun_xdp_one() tun_xdp_one() returns -EINVAL on a frame shorter than ETH_HLEN without freeing the page that vhost_net_build_xdp() allocated for it. tun_sendmsg() discards that -EINVAL and still returns total_len, so vhost_tx_batch() takes the success path and never frees the page; each short frame in a batch leaks one page-frag chunk. A local process that can open /dev/net/tun and /dev/vhost-net can hit this path: it attaches a tun/tap device as the vhost-net backend and feeds TX descriptors whose length minus the virtio-net header is below ETH_HLEN. Each kick leaks the page-frag chunks for that batch, and a tight submission loop exhausts host memory and triggers an OOM panic. Free the page before returning -EINVAL, matching the XDP-program error path in the same function. Fixes: 049584807f1d ("tun: add missing verification for short frame") Reported-by: Xiang Mei Signed-off-by: Weiming Shi Reviewed-by: Dongli Zhang Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260520160020.375349-2-bestswngs@gmail.com Signed-off-by: Jakub Kicinski --- drivers/net/tun.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index b183189f1853..f594360d66d6 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -2394,8 +2394,10 @@ static int tun_xdp_one(struct tun_struct *tun, bool skb_xdp = false; struct page *page; - if (unlikely(datasize < ETH_HLEN)) + if (unlikely(datasize < ETH_HLEN)) { + put_page(virt_to_head_page(xdp->data)); return -EINVAL; + } xdp_prog = rcu_dereference(tun->xdp_prog); if (xdp_prog) {