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ALSA: line6: Fix racy access to midibuf

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commit 15b7a03205 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: 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: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Takashi Iwai 2024-08-05 15:01:28 +02:00 committed by Greg Kroah-Hartman
parent c763dfe094
commit a54da4b787
1 changed files with 5 additions and 0 deletions
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5
sound/usb/line6/driver.c
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@ -286,12 +286,14 @@ static void line6_data_received(struct urb *urb)
{ {
struct usb_line6 *line6 = (struct usb_line6 *)urb->context; struct usb_line6 *line6 = (struct usb_line6 *)urb->context;
struct midi_buffer *mb = &line6->line6midi->midibuf_in; struct midi_buffer *mb = &line6->line6midi->midibuf_in;
unsigned long flags;
int done; int done;
if (urb->status == -ESHUTDOWN) if (urb->status == -ESHUTDOWN)
return; return;
if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) { if (line6->properties->capabilities & LINE6_CAP_CONTROL_MIDI) {
spin_lock_irqsave(&line6->line6midi->lock, flags);
done = done =
line6_midibuf_write(mb, urb->transfer_buffer, urb->actual_length); line6_midibuf_write(mb, urb->transfer_buffer, urb->actual_length);
@ -300,12 +302,15 @@ static void line6_data_received(struct urb *urb)
dev_dbg(line6->ifcdev, "%d %d buffer overflow - message skipped\n", dev_dbg(line6->ifcdev, "%d %d buffer overflow - message skipped\n",
done, urb->actual_length); done, urb->actual_length);
} }
spin_unlock_irqrestore(&line6->line6midi->lock, flags);
for (;;) { for (;;) {
spin_lock_irqsave(&line6->line6midi->lock, flags);
done = done =
line6_midibuf_read(mb, line6->buffer_message, line6_midibuf_read(mb, line6->buffer_message,
LINE6_MIDI_MESSAGE_MAXLEN, LINE6_MIDI_MESSAGE_MAXLEN,
LINE6_MIDIBUF_READ_RX); LINE6_MIDIBUF_READ_RX);
spin_unlock_irqrestore(&line6->line6midi->lock, flags);
if (done <= 0) if (done <= 0)
break; break;