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Commit 643293b6 authored by Takashi Iwai's avatar Takashi Iwai Committed by Greg Kroah-Hartman
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ALSA: line6: Fix racy access to midibuf 



commit 15b7a03205b31bc5623378c190d22b7ff60026f1 upstream.

There can be concurrent accesses to line6 midibuf from both the URB
completion callback and the rawmidi API access.  This could be a cause
of KMSAN warning triggered by syzkaller below (so put as reported-by
here).

This patch protects the midibuf call of the former code path with a
spinlock for avoiding the possible races.

Reported-by: default avatar <syzbot+78eccfb8b3c9a85fc6c5@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/00000000000000949c061df288c5@google.com
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20240805130129.10872-1-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 81964823

sound/usb/line6/driver.c

+5 −0
Original line number Diff line number Diff line
@@ -300,12 +300,14 @@ static void line6_data_received(struct urb *urb) 
{

	struct usb_line6 *line6 = (struct usb_line6 *)urb->context;

	struct midi_buffer *mb = &line6->line6midi->midibuf_in;

	unsigned long flags;

	int done;



	if (urb->status == -ESHUTDOWN)

		return;



	if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {

		spin_lock_irqsave(&line6->line6midi->lock, flags);

		done =

			line6_midibuf_write(mb, urb->transfer_buffer, urb->actual_length);
@@ -314,12 +316,15 @@ static void line6_data_received(struct urb *urb) 
			dev_dbg(line6->ifcdev, "%d %d buffer overflow - message skipped\n",

				done, urb->actual_length);

		}

		spin_unlock_irqrestore(&line6->line6midi->lock, flags);



		for (;;) {

			spin_lock_irqsave(&line6->line6midi->lock, flags);

			done =

				line6_midibuf_read(mb, line6->buffer_message,

						   LINE6_MIDI_MESSAGE_MAXLEN,

						   LINE6_MIDIBUF_READ_RX);

			spin_unlock_irqrestore(&line6->line6midi->lock, flags);



			if (done <= 0)

				break;