This is a note to let you know that I've just added the patch titled
ALSA: seq: Fix racy pool initializations
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: alsa-seq-fix-racy-pool-initializations.patch and it can be found in the queue-4.4 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 d15d662e89fc667b90cd294b0eb45694e33144da Mon Sep 17 00:00:00 2001
From: Takashi Iwai tiwai@suse.de Date: Mon, 12 Feb 2018 15:20:51 +0100 Subject: ALSA: seq: Fix racy pool initializations MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
From: Takashi Iwai tiwai@suse.de
commit d15d662e89fc667b90cd294b0eb45694e33144da upstream.
ALSA sequencer core initializes the event pool on demand by invoking snd_seq_pool_init() when the first write happens and the pool is empty. Meanwhile user can reset the pool size manually via ioctl concurrently, and this may lead to UAF or out-of-bound accesses since the function tries to vmalloc / vfree the buffer.
A simple fix is to just wrap the snd_seq_pool_init() call with the recently introduced client->ioctl_mutex; as the calls for snd_seq_pool_init() from other side are always protected with this mutex, we can avoid the race.
Reported-by: 范龙飞 long7573@126.com 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 | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -1012,7 +1012,7 @@ static ssize_t snd_seq_write(struct file { struct snd_seq_client *client = file->private_data; int written = 0, len; - int err = -EINVAL; + int err; struct snd_seq_event event;
if (!(snd_seq_file_flags(file) & SNDRV_SEQ_LFLG_OUTPUT)) @@ -1027,11 +1027,15 @@ static ssize_t snd_seq_write(struct file
/* allocate the pool now if the pool is not allocated yet */ if (client->pool->size > 0 && !snd_seq_write_pool_allocated(client)) { - if (snd_seq_pool_init(client->pool) < 0) + mutex_lock(&client->ioctl_mutex); + err = snd_seq_pool_init(client->pool); + mutex_unlock(&client->ioctl_mutex); + if (err < 0) return -ENOMEM; }
/* only process whole events */ + err = -EINVAL; while (count >= sizeof(struct snd_seq_event)) { /* Read in the event header from the user */ len = sizeof(event);
Patches currently in stable-queue which might be from tiwai@suse.de are
queue-4.4/alsa-hda-realtek-pci-quirk-for-fujitsu-u7x7.patch queue-4.4/alsa-usb-audio-fix-uac2-get_ctl-request-with-a-range-attribute.patch queue-4.4/alsa-hda-fix-headset-mic-detection-problem-for-two-dell-machines.patch queue-4.4/alsa-seq-fix-racy-pool-initializations.patch queue-4.4/alsa-seq-fix-regression-by-incorrect-ioctl_mutex-usages.patch queue-4.4/alsa-usb-audio-add-implicit-fb-quirk-for-behringer-ufx1204.patch