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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 09:20:42 +0200
commitca2523c9c569186e1e39f5f9db6b593d3f4ccf87 (patch)
tree516529db5029c8304902f9c687dfbb1863c98795 /include/sound
parent23709ae9b61429502fcd4686e7a97333f3b3544a (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 'include/sound')
-rw-r--r--include/sound/seq_virmidi.h1
1 files changed, 1 insertions, 0 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;
};