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Fri, 09 Jan 2026 02:47:08 -0800 (PST) Received: from DESKTOP-BKIPFGN ([209.141.36.37]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b17078dd8fsm12814933eec.20.2026.01.09.02.47.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Jan 2026 02:47:07 -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: Fri, 9 Jan 2026 18:46:44 +0800 Message-ID: <20260109104643.1988-2-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() previously registered the PF_XDP socket family before the per-net subsystem and other prerequisites (netdevice notifier, caches) were fully initialized. This exposed .create =3D xsk_create() to user space while per-netns state (net->xdp.lock/list) was still uninitialized. A task with CAP_NET_RAW could trigger this during boot/module load by calling socket(PF_XDP, SOCK_RAW, 0) concurrently with xsk_init(), leading to a NULL pointer dereference or use-after-free in the list manipulation. To fix this, move sock_register() to the end of the initialization sequence, ensuring that all required kernel structures are ready before exposing the AF_XDP interface to userspace. Accordingly, reorder the error unwind path to ensure proper cleanup in reverse order of initialization. Also, explicitly add kmem_cache_destroy() in the error path to prevent leaking xsk_tx_generic_cache if the registration fails. Fixes: c0c77d8fb787 ("xsk: add user memory registration support sockopt") Signed-off-by: Kery Qi --- net/xdp/xsk.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index f093c3453f64..d402f23dfd8e 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -1922,13 +1923,9 @@ 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; + goto out_proto; =20 err =3D register_netdevice_notifier(&xsk_netdev_notifier); if (err) @@ -1939,17 +1936,21 @@ static int __init xsk_init(void) 0, SLAB_HWCACHE_ALIGN, NULL); if (!xsk_tx_generic_cache) { err =3D -ENOMEM; - goto out_unreg_notif; + goto out_notifier; } =20 + err =3D sock_register(&xsk_family_ops); + if (err) + goto out_cache; + return 0; =20 -out_unreg_notif: +out_cache: + kmem_cache_destroy(xsk_tx_generic_cache); +out_notifier: 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: --=20 2.34.1