bpf: net_sched: Fix using bpf qdisc as default qdisc

Use bpf_try_module_get()/bpf_module_put() instead of try_module_get()/
module_put() when handling default qdisc since users can assign a bpf
qdisc to it.

To trigger the bug:
$ bpftool struct_ops register bpf_qdisc_fq.bpf.o /sys/fs/bpf
$ echo bpf_fq > /proc/sys/net/core/default_qdisc

Fixes: c8240344956e ("bpf: net_sched: Support implementation of Qdisc_ops in bpf")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250429192128.3860571-1-ameryhung@gmail.com

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index db6330258dda967c53ecab175a556221551f3620..c5e3673aadbe78562977ee0915153406c088daef 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -208,7 +208,7 @@ static struct Qdisc_ops *qdisc_lookup_default(const char *name)
 
        for (q = qdisc_base; q; q = q->next) {
                if (!strcmp(name, q->id)) {
-                       if (!try_module_get(q->owner))
+                       if (!bpf_try_module_get(q, q->owner))
                                q = NULL;
                        break;
                }
@@ -238,7 +238,7 @@ int qdisc_set_default(const char *name)
 
        if (ops) {
                /* Set new default */
-               module_put(default_qdisc_ops->owner);
+               bpf_module_put(default_qdisc_ops, default_qdisc_ops->owner);
                default_qdisc_ops = ops;
        }
        write_unlock(&qdisc_mod_lock);

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index fc5ef69359dbbcbb90c8213c84cf0a7230b54502..08e0e3aff97636cde7bdcf42a2713e45b56329ca 100644 (file)
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1002,14 +1002,14 @@ struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
 {
        struct Qdisc *sch;
 
-       if (!try_module_get(ops->owner)) {
+       if (!bpf_try_module_get(ops, ops->owner)) {
                NL_SET_ERR_MSG(extack, "Failed to increase module reference counter");
                return NULL;
        }
 
        sch = qdisc_alloc(dev_queue, ops, extack);
        if (IS_ERR(sch)) {
-               module_put(ops->owner);
+               bpf_module_put(ops, ops->owner);
                return NULL;
        }
        sch->parent = parentid;