netdev - Re: [PATCHv2 net] sctp: check stream reset info len before making reconf chunk

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Date:   Wed, 15 Nov 2017 10:35:58 -0500
From:   Neil Horman <nhorman@...driver.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem@...emloft.net,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        syzkaller@...glegroups.com
Subject: Re: [PATCHv2 net] sctp: check stream reset info len before making
 reconf chunk

On Wed, Nov 15, 2017 at 05:00:11PM +0800, Xin Long wrote:
> Now when resetting stream, if both in and out flags are set, the info
> len can reach:
>   sizeof(struct sctp_strreset_outreq) + SCTP_MAX_STREAM(65535) +
>   sizeof(struct sctp_strreset_inreq)  + SCTP_MAX_STREAM(65535)
> even without duplicated stream no, this value is far greater than the
> chunk's max size.
> 
> _sctp_make_chunk doesn't do any check for this, which would cause the
> skb it allocs is huge, syzbot even reported a crash due to this.
> 
> This patch is to check stream reset info len before making reconf
> chunk and return EINVAL if the len exceeds chunk's capacity.
> 
> Thanks Marcelo and Neil for making this clear.
> 
> v1->v2:
>   - move the check into sctp_send_reset_streams instead.
> 
> Fixes: cc16f00f6529 ("sctp: add support for generating stream reconf ssn reset request chunk")
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
Acked-by: Neil Horman <nhorman@...driver.com>