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Wed, 20 May 2026 09:00:38 -0700 (PDT) Received: from fx.tailc0aff1.ts.net ([206.206.192.132]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-30296dcb6e9sm23412317eec.16.2026.05.20.09.00.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2026 09:00:37 -0700 (PDT) From: Weiming Shi To: netdev@vger.kernel.org Cc: willemdebruijn.kernel@gmail.com, jasowang@redhat.com, pabeni@redhat.com, kuba@kernel.org, edumazet@google.com, dongli.zhang@oracle.com, xmei5@asu.edu, linux-kernel@vger.kernel.org, Weiming Shi Subject: [PATCH net] tun: free page on short-frame rejection in tun_xdp_one() Date: Wed, 20 May 2026 09:00:21 -0700 Message-ID: <20260520160020.375349-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Weiming Shi Reviewed-by: Dongli Zhang Reviewed-by: Willem de Bruijn --- 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 =3D false; struct page *page; =20 - if (unlikely(datasize < ETH_HLEN)) + if (unlikely(datasize < ETH_HLEN)) { + put_page(virt_to_head_page(xdp->data)); return -EINVAL; + } =20 xdp_prog =3D rcu_dereference(tun->xdp_prog); if (xdp_prog) { --=20 2.43.0