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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index efae143..a02512b 100644 (file)
--- 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 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;
@@ -1507,6 +1511,10 @@ 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;