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SubjectRe: [PATCH v6] sctp: fix refcount bug in sctp_wfree
On Fri, Mar 27, 2020 at 11:07:51AM +0800, Qiujun Huang wrote:
> We should iterate over the datamsgs to move
> all chunks(skbs) to newsk.
>
> The following case cause the bug:
> for the trouble SKB, it was in outq->transmitted list
>
> sctp_outq_sack
> sctp_check_transmitted
> SKB was moved to outq->sacked list
> then throw away the sack queue
> SKB was deleted from outq->sacked
> (but it was held by datamsg at sctp_datamsg_to_asoc
> So, sctp_wfree was not called here)
>
> then migrate happened
>
> sctp_for_each_tx_datachunk(
> sctp_clear_owner_w);
> sctp_assoc_migrate();
> sctp_for_each_tx_datachunk(
> sctp_set_owner_w);
> SKB was not in the outq, and was not changed to newsk
>
> finally
>
> __sctp_outq_teardown
> sctp_chunk_put (for another skb)
> sctp_datamsg_put
> __kfree_skb(msg->frag_list)
> sctp_wfree (for SKB)
> SKB->sk was still oldsk (skb->sk != asoc->base.sk).
>
> Reported-and-tested-by: syzbot+cea71eec5d6de256d54d@syzkaller.appspotmail.com
> Signed-off-by: Qiujun Huang <hqjagain@gmail.com>

Acked-by: Marcelo Ricardo Leitner <mleitner@redhat.com>
Thanks Qiujun.

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