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Tue, 21 Jul 2026 07:36:06 -0700 (PDT) From: "Cen Zhang (Microsoft)" To: aconole@redhat.com, echaudro@redhat.com, i.maximets@ovn.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: netdev@vger.kernel.org, dev@openvswitch.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, tgopinath@linux.microsoft.com, kys@microsoft.com, blbllhy@gmail.com Subject: [PATCH net] net/openvswitch: check Ethernet header length before key_extract() Date: Tue, 21 Jul 2026 10:36:02 -0400 Message-ID: <20260721143602.64677-1-blbllhy@gmail.com> X-Mailer: git-send-email 2.53.0 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" When a packet arrives on an ARPHRD_NONE device (e.g. TUN), ovs_flow_key_extract() trusts the user-provided skb->protocol field: if it is ETH_P_TEB, the packet is classified as MAC_PROTO_ETHERNET and key_extract() is called without ensuring the skb has ETH_HLEN (14) bytes of linear data. key_extract() unconditionally pulls 2 * ETH_ALEN bytes for MAC addresses and parse_ethertype() pulls 2 more, either of which triggers a kernel BUG in __skb_pull() when the linear area is too small. kernel BUG at include/linux/skbuff.h:2848! RIP: 0010:key_extract+0xa7e/0xd90 net/openvswitch/flow.c:933 ovs_flow_key_extract+0x419/0xa70 ovs_vport_receive+0x222/0x390 netdev_frame_hook+0x3e0/0x630 tun_get_user+0x2d0c/0x38e0 Fixed by adding check_header(skb, ETH_HLEN) in ovs_flow_key_extract() before calling key_extract(). Fixes: 217ac77a3c25 ("openvswitch: allow L3 netdev ports") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Cen Zhang (Microsoft) --- net/openvswitch/flow.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c index 66366982f604..a0f9d788d284 100644 --- a/net/openvswitch/flow.c +++ b/net/openvswitch/flow.c @@ -1035,6 +1035,13 @@ int ovs_flow_key_extract(const struct ip_tunnel_info= *tun_info, return res; key->mac_proto =3D res; =20 + if (res =3D=3D MAC_PROTO_ETHERNET) { + int err =3D check_header(skb, ETH_HLEN); + + if (unlikely(err)) + return err; + } + #if IS_ENABLED(CONFIG_NET_TC_SKB_EXT) if (tc_skb_ext_tc_enabled()) { tc_ext =3D skb_ext_find(skb, TC_SKB_EXT); --=20 2.53.0