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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Shuah Khan , Kuniyuki Iwashima , Hangbin Liu , Martin Karsten , Masashi Honma , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Leon Hwang Subject: [PATCH bpf-next v4 2/6] bpf: Add syscall common attrs support for xdp link_create Date: Sat, 24 Oct 2026 23:36:03 +0800 Message-ID: <20261024153608.58569-3-leon.hwang@linux.dev> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261024153608.58569-1-leon.hwang@linux.dev> References: <20261024153608.58569-1-leon.hwang@linux.dev> X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit With the syscall common attrs support for link_create, add syscall common attrs support for xdp link_create in order to report the invalid target ifindex error and the underlying driver's error. Instead of passing bpf log or extack to bpf_xdp_link_attach(), pass an errmsg pointer to receive the kstrdup() error msg, because 1) passing bpf log will introduce bpf_verifier.h dependency for net/core/dev.c, which is not acceptable for maintainability. 2) passing extack will access underlying driver string out of dev_put() guard, which will crash kernel when the device is unloaded concurrently. Signed-off-by: Leon Hwang --- include/linux/netdevice.h | 3 ++- kernel/bpf/syscall.c | 8 +++++++- net/core/dev.c | 6 +++++- 3 files changed, 14 insertions(+), 3 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index c0ae442c4344..e07b740604c7 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -4440,7 +4440,8 @@ struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *d struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev, struct netdev_queue *txq, int *ret); -int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog); +int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog, + char **errmsg); u8 dev_xdp_prog_count(struct net_device *dev); int netif_xdp_propagate(struct net_device *dev, struct netdev_bpf *bpf); int dev_xdp_propagate(struct net_device *dev, struct netdev_bpf *bpf); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index db870e795d04..675bff4d7aab 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -5868,6 +5868,7 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr, struct bpf_common_a struct bpf_verifier_log *log; struct bpf_log_attr attr_log; struct bpf_prog *prog; + char *errmsg = NULL; int ret; if (CHECK_ATTR(BPF_LINK_CREATE)) @@ -5944,7 +5945,7 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr, struct bpf_common_a break; #ifdef CONFIG_NET case BPF_PROG_TYPE_XDP: - ret = bpf_xdp_link_attach(attr, prog); + ret = bpf_xdp_link_attach(attr, prog, &errmsg); break; case BPF_PROG_TYPE_SCHED_CLS: if (attr->link_create.attach_type == BPF_TCX_INGRESS || @@ -5980,6 +5981,11 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr, struct bpf_common_a if (ret < 0) { int err; + if (errmsg) { + bpf_log(log, "%s\n", errmsg); + kfree(errmsg); + } + err = bpf_log_attr_finalize(&attr_log, log); ret = err ? err : ret; if (prog) diff --git a/net/core/dev.c b/net/core/dev.c index 1a09e7869118..da71c0d2120c 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10882,7 +10882,8 @@ static const struct bpf_link_ops bpf_xdp_link_lops = { .update_prog = bpf_xdp_link_update, }; -int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) +int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog, + char **errmsg) { struct net *net = current->nsproxy->net_ns; struct bpf_link_primer link_primer; @@ -10895,6 +10896,7 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) dev = dev_get_by_index(net, attr->link_create.target_ifindex); if (!dev) { rtnl_unlock(); + *errmsg = kstrdup("Invalid target_ifindex.", GFP_KERNEL); return -EINVAL; } @@ -10923,6 +10925,8 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) if (err) { link->dev = NULL; bpf_link_cleanup(&link_primer); + if (extack._msg) + *errmsg = kstrdup(extack._msg, GFP_KERNEL); trace_bpf_xdp_link_attach_failed(extack._msg); goto out_put_dev; } -- 2.55.0