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Sat, 19 Sep 2026 04:01:15 -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, co+ac0a8c41de69121d@bugs.sh, Weiming Shi , stable@vger.kernel.org Subject: [PATCH bpf v2 1/2] bpf: reject dev-bound-only programs on other devices Date: Sat, 19 Sep 2026 19:00:53 +0800 Message-ID: <20260919110053.497301-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260917161335.1020405-2-bestswngs@gmail.com> References: <20260917161335.1020405-2-bestswngs@gmail.com> 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. A bound-only program on an offload-registered netdev can instead inherit a real offdev and match a sibling port. With CAP_BPF and CAP_NET_ADMIN, a caller 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: Link: https://lore.kernel.org/bpf/20260917161335.1020405-2-bestswngs@gmail.com/ Assisted-by: LLM Signed-off-by: Weiming Shi --- Changes in v2: - Drop the redundant offdev NULL check. - State the capability requirements instead of using attacker wording. - Move the regression test to patch 2. kernel/bpf/offload.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c index 0d6f55695..d85539981 100644 --- a/kernel/bpf/offload.c +++ b/kernel/bpf/offload.c @@ -698,6 +698,8 @@ 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); -- 2.55.0