diff options
author | Takashi Iwai <tiwai@suse.de> | 2017-10-09 10:02:56 +0200 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-10-18 09:20:42 +0200 |
commit | ca2523c9c569186e1e39f5f9db6b593d3f4ccf87 (patch) | |
tree | 516529db5029c8304902f9c687dfbb1863c98795 | |
parent | 23709ae9b61429502fcd4686e7a97333f3b3544a (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>
-rw-r--r-- | include/sound/seq_virmidi.h | 1 | ||||
-rw-r--r-- | sound/core/seq/seq_virmidi.c | 27 |
2 files changed, 20 insertions, 8 deletions
diff --git a/include/sound/seq_virmidi.h b/include/sound/seq_virmidi.h index a03acd0d398a..695257ae64ac 100644 --- a/include/sound/seq_virmidi.h +++ b/include/sound/seq_virmidi.h @@ -60,6 +60,7 @@ struct snd_virmidi_dev { int port; /* created/attached port */ unsigned int flags; /* SNDRV_VIRMIDI_* */ rwlock_t filelist_lock; + struct rw_semaphore filelist_sem; struct list_head filelist; }; diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c index 81134e067184..3b126af4a026 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; |