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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: afe4fd0624 ("pkt_sched: fq: Fair Queue packet scheduler")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Diagnosed-by: Florian Westphal <fw@strlen.de>
Reported-by: syzbot+dc9071cc5a85950bdfce@syzkaller.appspotmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2020-01-06 06:10:39 -08:00 committed by David S. Miller
parent b969fee12b
commit d9e15a2733
1 changed files with 4 additions and 2 deletions
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6
net/sched/sch_fq.c
View File

@ -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])