Re: [PATCH] sctp: Don't add the shutdown timer if its already been added

From: Neil Horman <nhorman@tuxdriver.com>
Date: Tue, 19 May 2020 16:04:05 -0400

This BUG halt was reported a while back, but the patch somehow got
missed:

 ...

It appears that the side effect that starts the shutdown timer was processed
multiple times, which can happen as multiple paths can trigger it.  This of
course leads to the BUG halt in add_timer getting called.

Fix seems pretty straightforward, just check before the timer is added if its
already been started.  If it has mod the timer instead to min(current
expiration, new expiration)

Its been tested but not confirmed to fix the problem, as the issue has only
occured in production environments where test kernels are enjoined from being
installed.  It appears to be a sane fix to me though.  Also, recentely,
Jere found a reproducer posted on list to confirm that this resolves the
issues

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

Applied and queued up for -stable, thanks.