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 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

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-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 29159a4ed7044c52e3e2cf1a9fb55cec4745c60b Mon Sep 17 00:00:00 2001

From: Takashi Iwai tiwai@suse.de 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 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: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- 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 @@ -1416,6 +1416,10 @@ 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; @@ -1501,6 +1505,10 @@ 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 tiwai@suse.de are

queue-4.4/alsa-pcm-remove-incorrect-snd_bug_on-usages.patch queue-4.4/alsa-aloop-fix-inconsistent-format-due-to-incomplete-rule.patch queue-4.4/alsa-pcm-add-missing-error-checks-in-oss-emulation-plugin-builder.patch queue-4.4/alsa-pcm-abort-properly-at-pending-signal-in-oss-read-write-loops.patch queue-4.4/alsa-pcm-allow-aborting-mutex-lock-at-oss-read-write-loops.patch queue-4.4/alsa-aloop-fix-racy-hw-constraints-adjustment.patch queue-4.4/alsa-aloop-release-cable-upon-open-error-path.patch