Patch "ALSA: seq: Don't allow resizing pool in use" has been added to the 3.18-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ALSA: seq: Don't allow resizing pool in use

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     alsa-seq-don-t-allow-resizing-pool-in-use.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


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

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/core/seq/seq_clientmgr.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/core/seq/seq_clientmgr.c
+++ b/sound/core/seq/seq_clientmgr.c
@@ -1929,6 +1929,9 @@ static int snd_seq_ioctl_set_client_pool
 	    (! snd_seq_write_pool_allocated(client) ||
 	     info.output_pool != client->pool->size)) {
 		if (snd_seq_write_pool_allocated(client)) {
+			/* is the pool in use? */
+			if (atomic_read(&client->pool->counter))
+				return -EBUSY;
 			/* remove all existing cells */
 			snd_seq_pool_mark_closing(client->pool);
 			snd_seq_queue_client_leave_cells(client->number);


Patches currently in stable-queue which might be from tiwai@suse.de are

queue-3.18/alsa-seq-don-t-allow-resizing-pool-in-use.patch
queue-3.18/alsa-seq-more-protection-for-concurrent-write-and-ioctl-races.patch