diff options
| author | Eric Dumazet <edumazet@google.com> | 2025-06-11 11:15:14 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-06-12 08:05:50 -0700 |
| commit | d92adacdd8c2960be856e0b82acc5b7c5395fddb (patch) | |
| tree | 47f8d3e61bd87a9abe67ef44ad33a9ea3a87b2a3 /net | |
| parent | 43eb466041216d25dedaef1c383ad7bd89929cbc (diff) | |
net_sched: ets: fix a race in ets_qdisc_change()
Gerrard Tai reported a race condition in ETS, 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>
Link: https://patch.msgid.link/20250611111515.1983366-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sched/sch_ets.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/sched/sch_ets.c b/net/sched/sch_ets.c index 2c069f0181c6..037f764822b9 100644 --- a/net/sched/sch_ets.c +++ b/net/sched/sch_ets.c @@ -661,7 +661,7 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, for (i = q->nbands; i < oldbands; i++) { if (i >= q->nstrict && q->classes[i].qdisc->q.qlen) list_del_init(&q->classes[i].alist); - qdisc_tree_flush_backlog(q->classes[i].qdisc); + qdisc_purge_queue(q->classes[i].qdisc); } WRITE_ONCE(q->nstrict, nstrict); memcpy(q->prio2band, priomap, sizeof(priomap)); |