[PATCH 3.2 089/140] ALSA: pcm: Abort properly at pending signal in OSS read/write loops

Ben Hutchings
2018-02-28T17:27:33Z

From: Takashi Iwai <tiwai@suse.de>

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: Ben Hutchings <ben@decadent.org.uk>
---
sound/core/oss/pcm_oss.c | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1422,6 +1422,10 @@ static ssize_t snd_pcm_oss_write1(struct
tmp != runtime->oss.period_bytes)
break;
}
+ if (signal_pending(current)) {
+ tmp = -ERESTARTSYS;
+ goto err;
+ }
}
mutex_unlock(&runtime->oss.params_lock);
return xfer;
@@ -1507,6 +1511,10 @@ static ssize_t snd_pcm_oss_read1(struct
bytes -= tmp;
xfer += tmp;
}
+ if (signal_pending(current)) {
+ tmp = -ERESTARTSYS;
+ goto err;
+ }
}
mutex_unlock(&runtime->oss.params_lock);
return xfer;