From 5803b023881857db32ffefa0d269c90280a67ee0 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Mon, 9 Oct 2017 10:02:56 +0200 Subject: ALSA: seq: Fix copy_from_user() call inside lock 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 Cc: Signed-off-by: Takashi Iwai --- include/sound/seq_virmidi.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/sound/seq_virmidi.h') 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; }; -- cgit v1.2.3