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[34.145.139.141]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7d38bf2f84esm8032277b3.31.2026.05.22.06.39.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 May 2026 06:39:34 -0700 (PDT) Date: Fri, 22 May 2026 09:39:34 -0400 From: Willem de Bruijn To: Weiming Shi , 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 Message-ID: In-Reply-To: <20260520160020.375349-2-bestswngs@gmail.com> References: <20260520160020.375349-2-bestswngs@gmail.com> Subject: Re: [PATCH net] tun: free page on short-frame rejection in tun_xdp_one() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Weiming Shi wrote: > 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: Willem de Bruijn