Allow .init to proceed if qdisc_lookup() returns NULL as it only happens
when called by qdisc_create_dflt() in mq/mqprio_init and the parent qdisc
has not been added to qdisc_hash yet. In qdisc_create(), the caller,
__tc_modify_qdisc(), would have made sure the parent qdisc already exist.
In addition, call qdisc_watchdog_init() whether .init succeeds or not to
prevent null-pointer dereference. In qdisc_create() and
qdisc_create_dflt(), if .init fails, .destroy will be called. As a
result, the destroy epilogue could call qdisc_watchdog_cancel() with an
uninitialized timer, causing null-pointer deference in hrtimer_cancel().
Fixes: Fixes: c8240344956e ("bpf: net_sched: Support implementation of Qdisc_ops in bpf")
Signed-off-by: Amery Hung <ameryhung@xxxxxxxxx>
---
net/sched/bpf_qdisc.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c
index 9f32b305636f..a8efc3ff2b7e 100644
--- a/net/sched/bpf_qdisc.c
+++ b/net/sched/bpf_qdisc.c
@@ -234,18 +234,20 @@ __bpf_kfunc int bpf_qdisc_init_prologue(struct Qdisc *sch,
struct net_device *dev = qdisc_dev(sch);
struct Qdisc *p;
+ qdisc_watchdog_init(&q->watchdog, sch);
+
if (sch->parent != TC_H_ROOT) {
+ /* If qdisc_lookup() returns NULL, it means .init is called by
+ * qdisc_create_dflt() in mq/mqprio_init and the parent qdisc
+ * has not been added to qdisc_hash yet.
+ */
p = qdisc_lookup(dev, TC_H_MAJ(sch->parent));
- if (!p)
- return -ENOENT;
-
- if (!(p->flags & TCQ_F_MQROOT)) {
+ if (p && !(p->flags & TCQ_F_MQROOT)) {
NL_SET_ERR_MSG(extack, "BPF qdisc only supported on root or mq");
return -EINVAL;
}
}
- qdisc_watchdog_init(&q->watchdog, sch);
return 0;
}
--
2.47.1
