[PATCH 5.15 021/107] net: sched: tbf: dont call qdisc_put() while holding tree lock

Greg Kroah-Hartman
2022-09-06T13:50:55Z

From: Zhengchao Shao <shaozhengchao@huawei.com>

[ Upstream commit b05972f01e7d30419987a1f221b5593668fd6448 ]

The issue is the same to commit c2999f7fb05b ("net: sched: multiq: don't
call qdisc_put() while holding tree lock"). Qdiscs call qdisc_put() while
holding sch tree spinlock, which results sleeping-while-atomic BUG.

Fixes: c266f64dbfa2 ("net: sched: protect block state with mutex")
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Link: https://lore.kernel.org/r/20220826013930.340121-1-shaozhengchao@huawei.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/sch_tbf.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 78e79029dc631..6eb17004a9e44 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -342,6 +342,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
struct nlattr *tb[TCA_TBF_MAX + 1];
struct tc_tbf_qopt *qopt;
struct Qdisc *child = NULL;
+ struct Qdisc *old = NULL;
struct psched_ratecfg rate;
struct psched_ratecfg peak;
u64 max_size;
@@ -433,7 +434,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
sch_tree_lock(sch);
if (child) {
qdisc_tree_flush_backlog(q->qdisc);
- qdisc_put(q->qdisc);
+ old = q->qdisc;
q->qdisc = child;
}
q->limit = qopt->limit;
@@ -453,6 +454,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt,
memcpy(&q->peak, &peak, sizeof(struct psched_ratecfg));

sch_tree_unlock(sch);
+ qdisc_put(old);
err = 0;

tbf_offload_change(sch);
--
2.35.1