From 3bad09df43577f98cbf45a6aecf0d8b061ee4325 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Mon, 9 Oct 2017 10:02:56 +0200 Subject: [PATCH] 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 Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- Reading git-format-patch failed