Re: [PATCHv2 bpf-next 09/23] bpf: Add support for tracing multi link

On Wed, Mar 04, 2026 at 11:02:30PM +0000, bot+bpf-ci@kernel.org wrote:

quoted

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

[ ... ]

quoted

+int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
+{
+	struct bpf_tracing_multi_link *link = NULL;
+	struct bpf_link_primer link_primer;
+	u32 cnt, *ids = NULL;
+	u32 __user *uids;
+	int err;
+
+	uids = u64_to_user_ptr(attr->link_create.tracing_multi.ids);
+	cnt = attr->link_create.tracing_multi.cnt;
+
+	if (!cnt || !uids)
+		return -EINVAL;

Should attr->link_create.flags be validated here as well?

Both bpf_kprobe_multi_link_attach() and bpf_uprobe_multi_link_attach()
reject non-zero flags:

kernel/trace/bpf_trace.c:bpf_kprobe_multi_link_attach() {
    ...
    if (attr->link_create.flags)
        return -EINVAL;
    ...
}

argh right, that's missing, will fix, thnx

Without this check, userspace passing flags != 0 will be silently
accepted, which would prevent using the flags field for future
extensions since old kernels could not be distinguished from new
ones.

quoted

+	if (cnt > MAX_TRACING_MULTI_CNT)
+		return -E2BIG;

[ ... ]

quoted

+#else
+
+int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
+{
+	return -EOPNOTSUPP;
+}
+
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS) && CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS */

Minor: there is a stray ')' after CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
in this comment.

yep, will remove, thnx

jirka