From 9bb4bb18ccffc4dc4a1f1038a5dc0fb3a4020c05 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Mon, 8 Jan 2018 13:58:31 +0100
Subject: [PATCH] ALSA: pcm: Abort properly at pending signal in OSS read/write
 loops

commit 29159a4ed7044c52e3e2cf1a9fb55cec4745c60b upstream.

The loops for read and write in PCM OSS emulation have no proper check
of pending signals, and they keep processing even after user tries to
break.  This results in a very long delay, often seen as RCU stall
when a huge unprocessed bytes remain queued.  The bug could be easily
triggered by syzkaller.

As a simple workaround, this patch adds the proper check of pending
signals and aborts the loop appropriately.

Reported-by: syzbot+993cb4cfcbbff3947c21@syzkaller.appspotmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 sound/core/oss/pcm_oss.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 4a5bcf178982..d2a9e0fd46b0 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1416,6 +1416,10 @@ static ssize_t snd_pcm_oss_write1(struct snd_pcm_substream *substream, const cha
 			    tmp != runtime->oss.period_bytes)
 				break;
 		}
+		if (signal_pending(current)) {
+			tmp = -ERESTARTSYS;
+			goto err;
+		}
 	}
 	mutex_unlock(&runtime->oss.params_lock);
 	return xfer;
@@ -1501,6 +1505,10 @@ static ssize_t snd_pcm_oss_read1(struct snd_pcm_substream *substream, char __use
 			bytes -= tmp;
 			xfer += tmp;
 		}
+		if (signal_pending(current)) {
+			tmp = -ERESTARTSYS;
+			goto err;
+		}
 	}
 	mutex_unlock(&runtime->oss.params_lock);
 	return xfer;
-- 
2.30.9