Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux

ALSA: firewire-motu: fix truncated bytes in message tracepoints

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>

authored by

Takashi Sakamoto and committed by
Takashi Iwai
cb1bcf5e 77ff9e7b

+4 -3
+4 -3
sound/firewire/motu/amdtp-motu.c
··· 276 276 277 277 /* This is just for v2/v3 protocol. */ 278 278 for (i = 0; i < data_blocks; ++i) { 279 - *frames = (be32_to_cpu(buffer[1]) << 16) | 280 - (be32_to_cpu(buffer[2]) >> 16); 279 + *frames = be32_to_cpu(buffer[1]); 280 + *frames <<= 16; 281 + *frames |= be32_to_cpu(buffer[2]) >> 16; 282 + ++frames; 281 283 buffer += data_block_quadlets; 282 - frames++; 283 284 } 284 285 } 285 286