[PATCH 5.14 036/172] ALSA: firewire-motu: fix truncated bytes in message tracepoints

Greg Kroah-Hartman
2021-10-04T13:30:07Z

From: Takashi Sakamoto <o-takashi@sakamocchi.jp>

commit cb1bcf5ed536747013fe2b3f9bd56ce3242c295a upstream.

In MOTU protocol v2/v3, first two data chunks across 2nd and 3rd data
channels includes message bytes from device. The total size of message
is 48 bits per data block.

The 'data_block_message' tracepoints event produced by ALSA firewire-motu
driver exposes the sequence of messages to userspace in 64 bit storage,
however lower 32 bits are actually available since current implementation
truncates 16 bits in upper of the message as a result of bit shift
operation within 32 bit storage.

This commit fixes the bug by perform the bit shift in 64 bit storage.

Fixes: c6b0b9e65f09 ("ALSA: firewire-motu: add tracepoints for messages for unique protocol")
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210920110734.27161-1-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/firewire/motu/amdtp-motu.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/sound/firewire/motu/amdtp-motu.c
+++ b/sound/firewire/motu/amdtp-motu.c
@@ -276,10 +276,11 @@ static void __maybe_unused copy_message(

/* This is just for v2/v3 protocol. */
for (i = 0; i < data_blocks; ++i) {
- *frames = (be32_to_cpu(buffer[1]) << 16) |
- (be32_to_cpu(buffer[2]) >> 16);
+ *frames = be32_to_cpu(buffer[1]);
+ *frames <<= 16;
+ *frames |= be32_to_cpu(buffer[2]) >> 16;
+ ++frames;
buffer += data_block_quadlets;
- frames++;
}
}