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Thu, 08 Jan 2026 03:37:21 -0800 (PST) Received: from DESKTOP-BKIPFGN ([45.43.86.16]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-59b6cb7ed38sm1453663e87.44.2026.01.08.03.37.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jan 2026 03:37:21 -0800 (PST) From: Kery Qi To: bpf@vger.kernel.org Cc: linux-kernel@vger.kernel.org, bjorn@kernel.org, hawk@kernel.org, pabeni@redhat.com, magnus.karlsson@intel.com, daniel@iogearbox.net, maciej.fijalkowski@intel.com, kuba@kernel.org, edumazet@google.com, horms@kernel.org, ast@kernel.org, sdf@fomichev.me, john.fastabend@gmail.com, Kery Qi Subject: [PATCH bpf] xsk: fix init race causing NPD/UAF in xsk_create() Date: Thu, 8 Jan 2026 19:37:06 +0800 Message-ID: <20260108113706.1715-1-qikeyu2017@gmail.com> X-Mailer: git-send-email 2.50.1.windows.1 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" xsk_init() registers the PF_XDP socket family before xsk_net_ops. This exposes .create =3D xsk_create() to user space while per-netns state (net->xdp.lock/list) is still uninitialized. A task with CAP_NET_RAW can trigger this during boot/module load by calling socket(PF_XDP/AF_XDP, SOCK_RAW, 0) concurrently with xsk_init(), leading to NULL deref, list/lock corruption or use-after-free. Register the pernet subsystem (and prerequisites) first and only then sock_register() PF_XDP. Update the error unwind to match the new order. Similar to CVE-2024-26793 (GTP init ordering bug). Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt") Signed-off-by: Kery Qi --- net/xdp/xsk.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index f093c3453f64..63b48e4b8b65 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -1922,10 +1922,6 @@ static int __init xsk_init(void) if (err) goto out; =20 - err =3D sock_register(&xsk_family_ops); - if (err) - goto out_proto; - err =3D register_pernet_subsys(&xsk_net_ops); if (err) goto out_sk; @@ -1942,16 +1938,20 @@ static int __init xsk_init(void) goto out_unreg_notif; } =20 + err =3D sock_register(&xsk_family_ops); + if (err) + goto out_proto; + return 0; =20 out_unreg_notif: unregister_netdevice_notifier(&xsk_netdev_notifier); out_pernet: unregister_pernet_subsys(&xsk_net_ops); -out_sk: - sock_unregister(PF_XDP); out_proto: proto_unregister(&xsk_proto); +out_sk: + sock_unregister(PF_XDP); out: return err; } --=20 2.34.1