[PATCH] net: net_prio: Block attach if a socket is shared

[Daniel Wagner]

---
 net/core/netprio_cgroup.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 847c02b..de4e6c5 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -274,9 +274,39 @@ static struct cftype ss_files[] = {
 	{ }	/* terminate */
 };
 
+static int check_cnt(const void *v, struct file *file, unsigned n)
+{
+	unsigned *flag = (unsigned *)v;
+	int err;
+
+	struct socket *sock = sock_from_file(file, &err);
+	if (sock && file_count(file) > 1)
+		*flag = 1;
+
+	return 0;
+}
+
+static int cgrp_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
+{
+	struct task_struct *p;
+	unsigned flag = 0;
+
+	cgroup_taskset_for_each(p, cgrp, tset) {
+		task_lock(p);
+		iterate_fd(p->files, 0, check_cnt, &flag);
+		task_unlock(p);
+	}
+
+	if (flag != 0)
+		return -EINVAL;
+
+	return 0;
+}
+
 struct cgroup_subsys net_prio_subsys = {
 	.name		= "net_prio",
 	.create		= cgrp_create,
+	.can_attach	= cgrp_can_attach,
 	.destroy	= cgrp_destroy,
 	.attach		= net_prio_attach,
 	.subsys_id	= net_prio_subsys_id,
-- 
1.8.0.rc0



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