netdev - Re: [Patch net] net_sched: fix datalen for ematch

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Message-ID: <317521e6-07f5-c32a-66dd-8aa499ae80d7@gmail.com>
Date:   Wed, 22 Jan 2020 15:45:34 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc:     syzbot+5af9a90dad568aa9f611@...kaller.appspotmail.com,
        syzbot+2f07903a5b05e7f36410@...kaller.appspotmail.com,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [Patch net] net_sched: fix datalen for ematch



On 1/22/20 3:42 PM, Cong Wang wrote:
> syzbot reported an out-of-bound access in em_nbyte. As initially
> analyzed by Eric, this is because em_nbyte sets its own em->datalen
> in em_nbyte_change() other than the one specified by user, but this
> value gets overwritten later by its caller tcf_em_validate().
> We should leave em->datalen untouched to respect their choices.
> 
> I audit all the in-tree ematch users, all of those implement
> ->change() set em->datalen, so we can just avoid setting it twice
> in this case.
> 
> Reported-and-tested-by: syzbot+5af9a90dad568aa9f611@...kaller.appspotmail.com
> Reported-by: syzbot+2f07903a5b05e7f36410@...kaller.appspotmail.com
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---
>

SGTM, thanks.

Reviewed-by: Eric Dumazet <edumazet@...gle.com>