diff options
| author |   Eric Dumazet <edumazet@google.com> | 2025-06-11 11:15:13 +0000 |
|---|---|---|
| committer |   Jakub Kicinski <kuba@kernel.org> | 2025-06-12 08:05:50 -0700 |
| commit | 43eb466041216d25dedaef1c383ad7bd89929cbc (patch) | |
| tree | 23e2b2fa7716bbc39e9f19585d2143f489b6a73f | |
| parent | net_sched: red: fix a race in __red_change() (diff) | |
| download | wireguard-linux-43eb466041216d25dedaef1c383ad7bd89929cbc.tar.xz wireguard-linux-43eb466041216d25dedaef1c383ad7bd89929cbc.zip | |
net_sched: tbf: fix a race in tbf_change()
Gerrard Tai reported a race condition in TBF, whenever SFQ perturb timer
fires at the wrong time.
The race is as follows:
CPU 0 CPU 1
[1]: lock root
[2]: qdisc_tree_flush_backlog()
[3]: unlock root
|
| [5]: lock root
| [6]: rehash
| [7]: qdisc_tree_reduce_backlog()
|
[4]: qdisc_put()
This can be abused to underflow a parent's qlen.
Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog()
should fix the race, because all packets will be purged from the qdisc
before releasing the lock.
Fixes: b05972f01e7d ("net: sched: tbf: don't call qdisc_put() while holding tree lock")
Reported-by: Gerrard Tai <gerrard.tai@starlabs.sg>
Suggested-by: Gerrard Tai <gerrard.tai@starlabs.sg>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Zhengchao Shao <shaozhengchao@huawei.com>
Link: https://patch.msgid.link/20250611111515.1983366-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/sched/sch_tbf.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c index dc26b22d53c7..4c977f049670 100644 --- a/net/sched/sch_tbf.c +++ b/net/sched/sch_tbf.c @@ -452,7 +452,7 @@ static int tbf_change(struct Qdisc *sch, struct nlattr *opt, sch_tree_lock(sch); if (child) { - qdisc_tree_flush_backlog(q->qdisc); + qdisc_purge_queue(q->qdisc); old = q->qdisc; q->qdisc = child; } |