ALSA: aloop: Fix access to not-yet-ready substream via cable
authorTakashi Iwai <tiwai@suse.de>
Thu, 22 Mar 2018 09:40:27 +0000 (10:40 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 28 Mar 2018 16:24:29 +0000 (18:24 +0200)
commit88079d335aac8c37e6ebdc142baab6ec34e27955
treeb1ec6bc618e1833058d86f9005c1b0fa9ebc367e
parent1fcbcfff716f8d495ec3790264bc3250c4b87e2f
ALSA: aloop: Fix access to not-yet-ready substream via cable

commit 8e6b1a72a75bb5067ccb6b56d8ca4aa3a300a64e upstream.

In loopback_open() and loopback_close(), we assign and release the
substream object to the corresponding cable in a racy way.  It's
neither locked nor done in the right position.  The open callback
assigns the substream before its preparation finishes, hence the other
side of the cable may pick it up, which may lead to the invalid memory
access.

This patch addresses these: move the assignment to the end of the open
callback, and wrap with cable->lock for avoiding concurrent accesses.

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sound/drivers/aloop.c