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Subject[PATCH 4.14 54/62] pkt_sched: fq: do not accept silly TCA_FQ_QUANTUM
Date
From: Eric Dumazet <edumazet@google.com>

[ Upstream commit d9e15a2733067c9328fb56d98fe8e574fa19ec31 ]

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 <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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_fq.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -734,7 +734,7 @@ static int fq_change(struct Qdisc *sch,
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
err = -EINVAL;

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