From: Takashi Iwai tiwai@suse.de

[ Upstream commit d683469b3c93d7e2afd39e6e1970f24700eb7a68 ]

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: Sasha Levin sashal@kernel.org --- sound/usb/line6/driver.c | 2 +- sound/usb/line6/midibuf.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c index bbcb0d4d83aec..0193d4989107b 100644 --- a/sound/usb/line6/driver.c +++ b/sound/usb/line6/driver.c @@ -320,7 +320,7 @@ 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; diff --git a/sound/usb/line6/midibuf.c b/sound/usb/line6/midibuf.c index 36a610ba342ec..c931d48801ebe 100644 --- a/sound/usb/line6/midibuf.c +++ b/sound/usb/line6/midibuf.c @@ -163,7 +163,7 @@ 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