Commit 0749daa8 authored by Cássio Gabriel's avatar Cássio Gabriel Committed by Takashi Iwai
Browse files

ALSA: firewire-tascam: Do not drop unread control events 



tscm_hwdep_read_queue() copies as many queued control events as fit in
the userspace buffer. When the buffer is smaller than the current
contiguous queue segment, length is rounded down to the number of bytes
that can be copied.

However, after copying that shortened length, the code advances pull_pos
to the original tail_pos, marking the whole contiguous segment as
consumed. Any events between the copied portion and tail_pos are lost.

Limit tail_pos to the position after the entries actually copied before
updating pull_pos. When the whole segment fits, this is equivalent to the
old tail_pos update; when the buffer is smaller, the remaining events
stay queued for the next read.

Fixes: a8c0d132 ("ALSA: firewire-tascam: notify events of change of state for userspace applications")
Cc: stable@vger.kernel.org
Suggested-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarCássio Gabriel <cassiogabrielcontato@gmail.com>
Reviewed-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Co-developed-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260503-alsa-firewire-tascam-read-queue-v2-1-126c6efd7642@gmail.com
parent f8078588

sound/firewire/tascam/tascam-hwdep.c

+1 −0
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ static long tscm_hwdep_read_queue(struct snd_tscm *tscm, char __user *buf, 
			length = rounddown(remained, sizeof(*entries));

		if (length == 0)

			break;

		tail_pos = head_pos + length / sizeof(*entries);



		spin_unlock_irq(&tscm->lock);

		if (copy_to_user(pos, &entries[head_pos], length))