# Re: \[PATCH v2\] sctp: Fix double free in sctp\_sendmsg\_to\_asoc

- From: David Miller \<davem@davemloft.net\>
- Date: 2018-03-15 18:32:47 
- List: netdev
- Page: https://ratatoskr.run/netdev/2018/03/11088681
- Thread: https://ratatoskr.run/linux-sctp/2018/03/11088683/t.md

```text
From: Neil Horman <nhorman@tuxdriver.com>
Date: Mon, 12 Mar 2018 14:15:25 -0400

> syzbot/kasan detected a double free in sctp_sendmsg_to_asoc:
> BUG: KASAN: use-after-free in sctp_association_free+0x7b7/0x930
> net/sctp/associola.c:332
> Read of size 8 at addr ffff8801d8006ae0 by task syzkaller914861/4202
 ...
> This was introduced by commit:
> f84af33 sctp: factor out sctp_sendmsg_to_asoc from sctp_sendmsg
> 
> As the newly refactored function moved the wait_for_sndbuf call to a
> point after the association was connected, allowing for peeloff events
> to occur, which in turn caused wait_for_sndbuf to return -EPIPE which
> was not caught by the logic that determines if an association should be
> freed or not.
> 
> Fix it the easy way by returning the ordering of
> sctp_primitive_ASSOCIATE and sctp_wait_for_sndbuf to the old order, to
> ensure that EPIPE will not happen.
> 
> Tested by myself using the syzbot reproducers with positive results
> 
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> CC: davem@davemloft.net
> CC: Xin Long <lucien.xin@gmail.com>
> Reported-by: <redacted>

Applied, thanks Neil.
```