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Message-Id: <1457391064-6660-53-git-send-email-kamal@canonical.com>
Date: Mon, 7 Mar 2016 14:47:23 -0800
From: Kamal Mostafa <kamal@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Takashi Iwai <tiwai@...e.de>, Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 052/273] ALSA: seq: Fix race at closing in virmidi driver
4.2.8-ckt5 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Takashi Iwai <tiwai@...e.de>
commit 2d1b5c08366acd46c35a2e9aba5d650cb5bf5c19 upstream.
The virmidi driver has an open race at closing its assigned rawmidi
device, and this may lead to use-after-free in
snd_seq_deliver_single_event().
Plug the hole by properly protecting the linked list deletion and
calling in the right order in snd_virmidi_input_close().
BugLink: http://lkml.kernel.org/r/CACT4Y+Zd66+w12fNN85-425cVQT=K23kWbhnCEcMB8s3us-Frw@mail.gmail.com
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Tested-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
sound/core/seq/seq_virmidi.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c
index 56e0f4cd..f297592 100644
--- a/sound/core/seq/seq_virmidi.c
+++ b/sound/core/seq/seq_virmidi.c
@@ -254,9 +254,13 @@ static int snd_virmidi_output_open(struct snd_rawmidi_substream *substream)
*/
static int snd_virmidi_input_close(struct snd_rawmidi_substream *substream)
{
+ struct snd_virmidi_dev *rdev = substream->rmidi->private_data;
struct snd_virmidi *vmidi = substream->runtime->private_data;
- snd_midi_event_free(vmidi->parser);
+
+ write_lock_irq(&rdev->filelist_lock);
list_del(&vmidi->list);
+ write_unlock_irq(&rdev->filelist_lock);
+ snd_midi_event_free(vmidi->parser);
substream->runtime->private_data = NULL;
kfree(vmidi);
return 0;
--
2.7.0
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