From dbf079a6ce85fca0215060dc15ca0a5543902861 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?C=C3=A1ssio=20Gabriel?= Date: Sun, 3 May 2026 21:55:52 -0300 Subject: [PATCH] ALSA: firewire-tascam: Do not drop unread control events MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 0749daa8eb5ab90334aaad3b0671efd7150d43b1 upstream. 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: a8c0d13267a4 ("ALSA: firewire-tascam: notify events of change of state for userspace applications") Cc: stable@vger.kernel.org Suggested-by: Takashi Sakamoto Signed-off-by: Cássio Gabriel Reviewed-by: Takashi Sakamoto Co-developed-by: Takashi Sakamoto Signed-off-by: Takashi Sakamoto Signed-off-by: Takashi Iwai Link: https://patch.msgid.link/20260503-alsa-firewire-tascam-read-queue-v2-1-126c6efd7642@gmail.com Signed-off-by: Greg Kroah-Hartman --- sound/firewire/tascam/tascam-hwdep.c | 1 + 1 file changed, 1 insertion(+) diff --git a/sound/firewire/tascam/tascam-hwdep.c b/sound/firewire/tascam/tascam-hwdep.c index 74eed9505665..9c3f68d8daef 100644 --- a/sound/firewire/tascam/tascam-hwdep.c +++ b/sound/firewire/tascam/tascam-hwdep.c @@ -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))