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Thu, 17 Sep 2026 09:14:07 -0700 (PDT) Received: from 192.168.50.3 ([198.176.50.208]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2dd89d8fd37sm29489395ad.3.2026.09.17.09.13.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Sep 2026 09:14:06 -0700 (PDT) From: bestswngs@gmail.com To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, bpf@vger.kernel.org, netdev@vger.kernel.org Cc: martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, davem@davemloft.net, kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, xmei5@asu.edu, Weiming Shi , stable@vger.kernel.org, co+ac0a8c41de69121d@bugs.sh Subject: [PATCH bpf] bpf: reject dev-bound-only programs on other devices Date: Fri, 18 Sep 2026 00:13:36 +0800 Message-ID: <20260917161335.1020405-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Weiming Shi __bpf_offload_dev_match() falls back to comparing offdev pointers after an exact netdev mismatch. Bound-only programs normally have NULL offdevs, so unrelated netdevs compare equal; one loaded on an offload-registered netdev can instead inherit a real offdev and match a sibling port. An attacker can use bpf(BPF_LINK_CREATE) with a different target ifindex to run metadata kfuncs specialized for the bound driver on the target driver's xdp_buff. Running a veth-bound program on tun reads beyond tun's bare stack xdp_buff as a veth_xdp_buff. Oops: general protection fault, probably for non-canonical address KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:veth_xdp_rx_timestamp (drivers/net/veth.c:1673) Call Trace: ... tun_build_skb (drivers/net/tun.c:1739) tun_get_user (drivers/net/tun.c:1856) tun_chr_write_iter (drivers/net/tun.c:2091) vfs_write (fs/read_write.c:595 fs/read_write.c:687) ksys_write (fs/read_write.c:739) do_syscall_64 (arch/x86/entry/syscall_64.c:84) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Kernel panic - not syncing: Fatal exception in interrupt Restrict non-offloaded programs to exact netdev matches and retain the shared-offdev fallback only for genuinely offloaded multi-port programs. Cc: stable@vger.kernel.org Fixes: 2b3486bc2d23 ("bpf: Introduce device-bound XDP programs") Reported-by: Assisted-by: LLM Signed-off-by: Weiming Shi --- kernel/bpf/offload.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c index 0d6f55695..8c91d00d4 100644 --- a/kernel/bpf/offload.c +++ b/kernel/bpf/offload.c @@ -698,11 +698,14 @@ static bool __bpf_offload_dev_match(struct bpf_prog *prog, return false; if (offload->netdev == netdev) return true; + if (!bpf_prog_is_offloaded(prog->aux)) + return false; ondev1 = bpf_offload_find_netdev(offload->netdev); ondev2 = bpf_offload_find_netdev(netdev); - return ondev1 && ondev2 && ondev1->offdev == ondev2->offdev; + return ondev1 && ondev2 && ondev1->offdev && + ondev1->offdev == ondev2->offdev; } bool bpf_offload_dev_match(struct bpf_prog *prog, struct net_device *netdev) -- 2.55.0