lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 21 Aug 2018 08:20:34 +0200
From:   Greg Kroah-Hartman <>
Cc:     Greg Kroah-Hartman <>,,,
        Takashi Iwai <>
Subject: [PATCH 4.18 08/35] ALSA: virmidi: Fix too long output trigger loop

4.18-stable review patch.  If anyone has any objections, please let me know.


From: Takashi Iwai <>

commit 50e9ffb1996a5d11ff5040a266585bad4ceeca0a upstream.

The virmidi output trigger tries to parse the all available bytes and
process sequencer events as much as possible.  In a normal situation,
this is supposed to be relatively short, but a program may give a huge
buffer and it'll take a long time in a single spin lock, which may
eventually lead to a soft lockup.

This patch simply adds a workaround, a cond_resched() call in the loop
if applicable.  A better solution would be to move the event processor
into a work, but let's put a duct-tape quickly at first.

Reported-and-tested-by: Dae R. Jeong <>
Cc: <>
Signed-off-by: Takashi Iwai <>
Signed-off-by: Greg Kroah-Hartman <>

 sound/core/seq/seq_virmidi.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

--- a/sound/core/seq/seq_virmidi.c
+++ b/sound/core/seq/seq_virmidi.c
@@ -163,6 +163,7 @@ static void snd_virmidi_output_trigger(s
 	int count, res;
 	unsigned char buf[32], *pbuf;
 	unsigned long flags;
+	bool check_resched = !in_atomic();
 	if (up) {
 		vmidi->trigger = 1;
@@ -200,6 +201,15 @@ static void snd_virmidi_output_trigger(s
 					vmidi->event.type = SNDRV_SEQ_EVENT_NONE;
+			if (!check_resched)
+				continue;
+			/* do temporary unlock & cond_resched() for avoiding
+			 * CPU soft lockup, which may happen via a write from
+			 * a huge rawmidi buffer
+			 */
+			spin_unlock_irqrestore(&substream->runtime->lock, flags);
+			cond_resched();
+			spin_lock_irqsave(&substream->runtime->lock, flags);
 		spin_unlock_irqrestore(&substream->runtime->lock, flags);

Powered by blists - more mailing lists