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authorTakashi Iwai <tiwai@suse.de>2017-10-09 10:02:56 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-10-18 09:35:40 +0200
commit6571ce8408811e56f2c70d093a6546c11b82fad3 (patch)
treed916c5d697297b924408cbd69375c8663ee2a422 /sound
parent35b84860667ff081eee56b62f3db2a28ca8a3823 (diff)
ALSA: seq: Fix copy_from_user() call inside lock
commit 5803b023881857db32ffefa0d269c90280a67ee0 upstream. The event handler in the virmidi sequencer code takes a read-lock for the linked list traverse, while it's calling snd_seq_dump_var_event() in the loop. The latter function may expand the user-space data depending on the event type. It eventually invokes copy_from_user(), which might be a potential dead-lock. The sequencer core guarantees that the user-space data is passed only with atomic=0 argument, but snd_virmidi_dev_receive_event() ignores it and always takes read-lock(). For avoiding the problem above, this patch introduces rwsem for non-atomic case, while keeping rwlock for atomic case. Also while we're at it: the superfluous irq flags is dropped in snd_virmidi_input_open(). Reported-by: Jia-Ju Bai <baijiaju1990@163.com> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound')
-rw-r--r--sound/core/seq/seq_virmidi.c27
1 files changed, 19 insertions, 8 deletions
diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c
index c82ed3e70506..200764948ed1 100644
--- a/sound/core/seq/seq_virmidi.c
+++ b/sound/core/seq/seq_virmidi.c
@@ -77,13 +77,17 @@ static void snd_virmidi_init_event(struct snd_virmidi *vmidi,
* decode input event and put to read buffer of each opened file
*/
static int snd_virmidi_dev_receive_event(struct snd_virmidi_dev *rdev,
- struct snd_seq_event *ev)
+ struct snd_seq_event *ev,
+ bool atomic)
{
struct snd_virmidi *vmidi;
unsigned char msg[4];
int len;
- read_lock(&rdev->filelist_lock);
+ if (atomic)
+ read_lock(&rdev->filelist_lock);
+ else
+ down_read(&rdev->filelist_sem);
list_for_each_entry(vmidi, &rdev->filelist, list) {
if (!vmidi->trigger)
continue;
@@ -97,7 +101,10 @@ static int snd_virmidi_dev_receive_event(struct snd_virmidi_dev *rdev,
snd_rawmidi_receive(vmidi->substream, msg, len);
}
}
- read_unlock(&rdev->filelist_lock);
+ if (atomic)
+ read_unlock(&rdev->filelist_lock);
+ else
+ up_read(&rdev->filelist_sem);
return 0;
}
@@ -115,7 +122,7 @@ int snd_virmidi_receive(struct snd_rawmidi *rmidi, struct snd_seq_event *ev)
struct snd_virmidi_dev *rdev;
rdev = rmidi->private_data;
- return snd_virmidi_dev_receive_event(rdev, ev);
+ return snd_virmidi_dev_receive_event(rdev, ev, true);
}
#endif /* 0 */
@@ -130,7 +137,7 @@ static int snd_virmidi_event_input(struct snd_seq_event *ev, int direct,
rdev = private_data;
if (!(rdev->flags & SNDRV_VIRMIDI_USE))
return 0; /* ignored */
- return snd_virmidi_dev_receive_event(rdev, ev);
+ return snd_virmidi_dev_receive_event(rdev, ev, atomic);
}
/*
@@ -209,7 +216,6 @@ static int snd_virmidi_input_open(struct snd_rawmidi_substream *substream)
struct snd_virmidi_dev *rdev = substream->rmidi->private_data;
struct snd_rawmidi_runtime *runtime = substream->runtime;
struct snd_virmidi *vmidi;
- unsigned long flags;
vmidi = kzalloc(sizeof(*vmidi), GFP_KERNEL);
if (vmidi == NULL)
@@ -223,9 +229,11 @@ static int snd_virmidi_input_open(struct snd_rawmidi_substream *substream)
vmidi->client = rdev->client;
vmidi->port = rdev->port;
runtime->private_data = vmidi;
- write_lock_irqsave(&rdev->filelist_lock, flags);
+ down_write(&rdev->filelist_sem);
+ write_lock_irq(&rdev->filelist_lock);
list_add_tail(&vmidi->list, &rdev->filelist);
- write_unlock_irqrestore(&rdev->filelist_lock, flags);
+ write_unlock_irq(&rdev->filelist_lock);
+ up_write(&rdev->filelist_sem);
vmidi->rdev = rdev;
return 0;
}
@@ -264,9 +272,11 @@ 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;
+ down_write(&rdev->filelist_sem);
write_lock_irq(&rdev->filelist_lock);
list_del(&vmidi->list);
write_unlock_irq(&rdev->filelist_lock);
+ up_write(&rdev->filelist_sem);
snd_midi_event_free(vmidi->parser);
substream->runtime->private_data = NULL;
kfree(vmidi);
@@ -520,6 +530,7 @@ int snd_virmidi_new(struct snd_card *card, int device, struct snd_rawmidi **rrmi
rdev->rmidi = rmidi;
rdev->device = device;
rdev->client = -1;
+ init_rwsem(&rdev->filelist_sem);
rwlock_init(&rdev->filelist_lock);
INIT_LIST_HEAD(&rdev->filelist);
rdev->seq_mode = SNDRV_VIRMIDI_SEQ_DISPATCH;