From d9e15a2733067c9328fb56d98fe8e574fa19ec31 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 6 Jan 2020 06:10:39 -0800 Subject: [PATCH] pkt_sched: fq: do not accept silly TCA_FQ_QUANTUM As diagnosed by Florian : If TCA_FQ_QUANTUM is set to 0x80000000, fq_deueue() can loop forever in : if (f->credit <= 0) { f->credit += q->quantum; goto begin; } ... because f->credit is either 0 or -2147483648. Let's limit TCA_FQ_QUANTUM to no more than 1 << 20 : This max value should limit risks of breaking user setups while fixing this bug. Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler") Signed-off-by: Eric Dumazet Diagnosed-by: Florian Westphal Reported-by: syzbot+dc9071cc5a85950bdfce@syzkaller.appspotmail.com Signed-off-by: David S. Miller --- net/sched/sch_fq.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index ff4c5e9d0d77..a5a295477ecc 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -786,10 +786,12 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt, if (tb[TCA_FQ_QUANTUM]) { u32 quantum = nla_get_u32(tb[TCA_FQ_QUANTUM]); - if (quantum > 0) + if (quantum > 0 && quantum <= (1 << 20)) { q->quantum = quantum; - else + } else { + NL_SET_ERR_MSG_MOD(extack, "invalid quantum"); err = -EINVAL; + } } if (tb[TCA_FQ_INITIAL_QUANTUM]) -- 2.30.2