CVE Request: Linux kernel - SCTP denial of service during heartbeat timeout functions.

[Wade Mealing <wmealing () redhat com>]

Gday all,

> From the patch[1] commit comments:

--
A case can occur when sctp_accept() is called by the user during
a heartbeat timeout event after the 4-way handshake.  Since
sctp_assoc_migrate() changes both assoc->base.sk and assoc->ep, the
bh_sock_lock in sctp_generate_heartbeat_event() will be taken with
the listening socket but released with the new association socket.
The result is a deadlock on any future attempts to take the listening
socket lock.

Note that this race can occur with other SCTP timeouts that take
the bh_lock_sock() in the event sctp_accept() is called.
---

TLDR: ensure that the lock on the socket taken is also the
same one that is released by saving a copy of the socket 
before entering the heartbeat event critical section.

I'd like a CVE for this issue. 

Thanks !

Wade Mealing
Red Hat Product Security

Resources:
https://bugzilla.redhat.com/show_bug.cgi?id=1297389
https://patchwork.ozlabs.org/patch/522412/

Patch commit notes (net-next.git):
[1] https://kernel.googlesource.com/pub/scm/linux/kernel/git/horms/ipvs/+/635682a14427d241bab7bbdeebb48a7d7b91638e