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bpf: net_sched: Fix bpf qdisc init prologue when set as default qdisc

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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: c824034495 ("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>
This commit is contained in:
Amery Hung
2025-05-02 13:16:20 -07:00
committed by Martin KaFai Lau
parent 1b1f563a25
commit 659b3b2c48
1 changed files with 8 additions and 6 deletions
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14
net/sched/bpf_qdisc.c
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@@ -234,18 +234,20 @@ __bpf_kfunc int bpf_qdisc_init_prologue(struct Qdisc *sch,
struct net_device *dev = qdisc_dev(sch);
struct Qdisc *p;
if (sch->parent != TC_H_ROOT) {
p = qdisc_lookup(dev, TC_H_MAJ(sch->parent));
if (!p)
return -ENOENT;
qdisc_watchdog_init(&q->watchdog, sch);
if (!(p->flags & TCQ_F_MQROOT)) {
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 && !(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;
}