On Tue, Mar 17, 2020 at 12:15 PM Marcelo Ricardo Leitner
[off-list ref] wrote:

On Mon, Mar 16, 2020 at 11:53:24AM +0800, Qiujun Huang wrote:

quoted

Do accounting for skb's real sk.
In some case skb->sk != asoc->base.sk.

This is a too simple description.  Please elaborate how this can
happen in sctp_wfree. Especially considering the construct for
migrating the tx queue on sctp_sock_migrate(), as both sockets are
locked while moving the chunks around and the asoc itself is only
moved in between decrementing and incrementing the refcount:

        lock_sock_nested(newsk, SINGLE_DEPTH_NESTING);
        sctp_for_each_tx_datachunk(assoc, sctp_clear_owner_w);
        sctp_assoc_migrate(assoc, newsk);
        sctp_for_each_tx_datachunk(assoc, sctp_set_owner_w);
        ...

Yeah, the description is too simple. I'll send v2.

quoted

Reported-and-tested-by: syzbot+cea71eec5d6de256d54d@syzkaller.appspotmail.com

I can't see a positive test result, though. If I didn't loose any
email, your last test with a patch similar to this one actually
failed.
I'm talking about syzbot test result at Message-ID: [ref]

I told with syzbot privately avoiding noise :p
Thanks!