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ALSA: line6: Fix endless MIDI read loop 

commit d683469b3c upstream.

The MIDI input event parser of the LINE6 driver may enter into an
endless loop when the unexpected data sequence is given, as it tries
to continue the secondary bytes without termination.  Also, when the
input data is too short, the parser returns a negative error, while
the caller doesn't handle it properly.  This would lead to the
unexpected behavior as well.

This patch addresses those issues by checking the return value
correctly and handling the one-byte event in the parser properly.

The bug was reported by syzkaller.

Reported-by: syzbot+cce32521ee0a824c21f7@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/000000000000033087059f8f8fa3@google.com
Link: https://lore.kernel.org/r/20200309095922.30269-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Takashi Iwai 2020-03-09 10:59:22 +01:00 committed by Greg Kroah-Hartman
parent 64ab82cf61
commit 2d994c9cef
2 changed files with 2 additions and 2 deletions
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2
sound/usb/line6/driver.c
View File

@ -305,7 +305,7 @@ static void line6_data_received(struct urb *urb)
line6_midibuf_read(mb, line6->buffer_message,
LINE6_MIDI_MESSAGE_MAXLEN);
if (done == 0)
if (done <= 0)
break;
line6->message_length = done;

2
sound/usb/line6/midibuf.c
View File

@ -159,7 +159,7 @@ int line6_midibuf_read(struct midi_buffer *this, unsigned char *data,
int midi_length_prev =
midibuf_message_length(this->command_prev);
if (midi_length_prev > 0) {
if (midi_length_prev > 1) {
midi_length = midi_length_prev - 1;
repeat = 1;
} else