From c96a7302975ce043f565c9ce2359794e1397488c Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Mon, 5 Mar 2018 22:00:55 +0100
Subject: [PATCH] ALSA: seq: Don't allow resizing pool in use
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commit d85739367c6d56e475c281945c68fdb05ca74b4c upstream.

This is a fix for a (sort of) fallout in the recent commit
d15d662e89fc ("ALSA: seq: Fix racy pool initializations") for
CVE-2018-1000004.
As the pool resize deletes the existing cells, it may lead to a race
when another thread is writing concurrently, eventually resulting a
UAF.

A simple workaround is not to allow the pool resizing when the pool is
in use.  It's an invalid behavior in anyway.

Fixes: d15d662e89fc ("ALSA: seq: Fix racy pool initializations")
Reported-by: 范龙飞 <long7573@126.com>
Reported-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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