Patch "ALSA: pcm: Abort properly at pending signal in OSS read/write loops" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

ALSA: pcm: Abort properly at pending signal in OSS read/write loops

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
alsa-pcm-abort-properly-at-pending-signal-in-oss-read-write-loops.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Mon, 8 Jan 2018 13:58:31 +0100
Subject: ALSA: pcm: Abort properly at pending signal in OSS read/write loops

From: Takashi Iwai <[email protected]>

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.

---
 sound/core/oss/pcm_oss.c |    8 ++++++++
 1 file changed, 8 insertions(+)

@@ -1381,6 +1381,10 @@ 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;

@@ -1466,6 +1470,10 @@ 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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/alsa-pcm-remove-incorrect-snd_bug_on-usages.patch queue-4.14/alsa-aloop-fix-inconsistent-format-due-to-incomplete-rule.patch queue-4.14/alsa-pcm-workaround-for-weird-pulseaudio-behavior-on-rewind-error.patch queue-4.14/alsa-pcm-add-missing-error-checks-in-oss-emulation-plugin-builder.patch queue-4.14/alsa-pcm-abort-properly-at-pending-signal-in-oss-read-write-loops.patch queue-4.14/alsa-pcm-allow-aborting-mutex-lock-at-oss-read-write-loops.patch queue-4.14/alsa-aloop-fix-racy-hw-constraints-adjustment.patch queue-4.14/alsa-aloop-release-cable-upon-open-error-path.patch