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ALSA: seq: Fix race at closing in virmidi driver
author
Takashi Iwai
<tiwai@suse.de>
Mon, 1 Feb 2016 11:06:42 +0000
(12:06 +0100)
committer
Greg Kroah-Hartman
<gregkh@linuxfoundation.org>
Wed, 17 Feb 2016 20:30:59 +0000
(12:30 -0800)
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@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sound/core/seq/seq_virmidi.c
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diff --git
a/sound/core/seq/seq_virmidi.c
b/sound/core/seq/seq_virmidi.c
index 09b26cb8265a1d4d9a7d952f8d552333c03395aa..81134e067184f36bdbd2abc0bb3f64354888a7d4 100644
(file)
--- a/
sound/core/seq/seq_virmidi.c
+++ b/
sound/core/seq/seq_virmidi.c
@@
-261,9
+261,13
@@
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;