netdev - Re: [PATCH net] sch_sfq: validate silly quantum values

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Message-Id: <20200427.115054.551269197453508231.davem@davemloft.net>
Date:   Mon, 27 Apr 2020 11:50:54 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        syzbot+0251e883fe39e7a0cb0a@...kaller.appspotmail.com,
        Jason@...c4.com
Subject: Re: [PATCH net] sch_sfq: validate silly quantum values

From: Eric Dumazet <edumazet@...gle.com>
Date: Sun, 26 Apr 2020 18:19:07 -0700

> syzbot managed to set up sfq so that q->scaled_quantum was zero,
> triggering an infinite loop in sfq_dequeue()
> 
> More generally, we must only accept quantum between 1 and 2^18 - 7,
> meaning scaled_quantum must be in [1, 0x7FFF] range.
> 
> Otherwise, we also could have a loop in sfq_dequeue()
> if scaled_quantum happens to be 0x8000, since slot->allot
> could indefinitely switch between 0 and 0x8000.
> 
> Fixes: eeaeb068f139 ("sch_sfq: allow big packets and be fair")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot+0251e883fe39e7a0cb0a@...kaller.appspotmail.com

Applied and queued up for -stable, thanks Eric.