[PATCH bpf-next v4 2/6] bpf: Add syscall common attrs support for xdp link_create
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WARM3d
SUPERSEDED
From: Leon Hwang <hidden>
Date: 2026-10-24 15:36:40
Also in:
bpf, linux-kselftest, lkml, netdev
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), networking drivers, networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Status: Superseded by v5 (posted 2026-10-26). [go to v5]
Revision v4 (5 revisions archived).
Revisions (5)
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 <redacted> --- 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