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[PATCH 4.4 28/31] ALSA: msnd: Optimize / harden DSP and MIDI loops

From Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups linux.kernel
Subject [PATCH 4.4 28/31] ALSA: msnd: Optimize / harden DSP and MIDI loops
Date 2017-09-12 19:20 +0200
Message-ID <uoX0T-48V-13@gated-at.bofh.it> (permalink)
References <uoWHv-3KO-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 20e2b791796bd68816fa115f12be5320de2b8021 upstream.

The ISA msnd drivers have loops fetching the ring-buffer head, tail
and size values inside the loops.  Such codes are inefficient and
fragile.

This patch optimizes it, and also adds the sanity check to avoid the
endless loops.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196131
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196133
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: grygorii tertychnyi <gtertych@cisco.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/isa/msnd/msnd_midi.c     |   28 ++++++++++++++--------------
 sound/isa/msnd/msnd_pinnacle.c |   23 ++++++++++++-----------
 2 files changed, 26 insertions(+), 25 deletions(-)

--- a/sound/isa/msnd/msnd_midi.c
+++ b/sound/isa/msnd/msnd_midi.c
@@ -120,24 +120,24 @@ void snd_msndmidi_input_read(void *mpuv)
 	unsigned long flags;
 	struct snd_msndmidi *mpu = mpuv;
 	void *pwMIDQData = mpu->dev->mappedbase + MIDQ_DATA_BUFF;
+	u16 head, tail, size;
 
 	spin_lock_irqsave(&mpu->input_lock, flags);
-	while (readw(mpu->dev->MIDQ + JQS_wTail) !=
-	       readw(mpu->dev->MIDQ + JQS_wHead)) {
-		u16 wTmp, val;
-		val = readw(pwMIDQData + 2 * readw(mpu->dev->MIDQ + JQS_wHead));
+	head = readw(mpu->dev->MIDQ + JQS_wHead);
+	tail = readw(mpu->dev->MIDQ + JQS_wTail);
+	size = readw(mpu->dev->MIDQ + JQS_wSize);
+	if (head > size || tail > size)
+		goto out;
+	while (head != tail) {
+		unsigned char val = readw(pwMIDQData + 2 * head);
 
-			if (test_bit(MSNDMIDI_MODE_BIT_INPUT_TRIGGER,
-				     &mpu->mode))
-				snd_rawmidi_receive(mpu->substream_input,
-						    (unsigned char *)&val, 1);
-
-		wTmp = readw(mpu->dev->MIDQ + JQS_wHead) + 1;
-		if (wTmp > readw(mpu->dev->MIDQ + JQS_wSize))
-			writew(0,  mpu->dev->MIDQ + JQS_wHead);
-		else
-			writew(wTmp,  mpu->dev->MIDQ + JQS_wHead);
+		if (test_bit(MSNDMIDI_MODE_BIT_INPUT_TRIGGER, &mpu->mode))
+			snd_rawmidi_receive(mpu->substream_input, &val, 1);
+		if (++head > size)
+			head = 0;
+		writew(head, mpu->dev->MIDQ + JQS_wHead);
 	}
+ out:
 	spin_unlock_irqrestore(&mpu->input_lock, flags);
 }
 EXPORT_SYMBOL(snd_msndmidi_input_read);
--- a/sound/isa/msnd/msnd_pinnacle.c
+++ b/sound/isa/msnd/msnd_pinnacle.c
@@ -170,23 +170,24 @@ static irqreturn_t snd_msnd_interrupt(in
 {
 	struct snd_msnd *chip = dev_id;
 	void *pwDSPQData = chip->mappedbase + DSPQ_DATA_BUFF;
+	u16 head, tail, size;
 
 	/* Send ack to DSP */
 	/* inb(chip->io + HP_RXL); */
 
 	/* Evaluate queued DSP messages */
-	while (readw(chip->DSPQ + JQS_wTail) != readw(chip->DSPQ + JQS_wHead)) {
-		u16 wTmp;
-
-		snd_msnd_eval_dsp_msg(chip,
-			readw(pwDSPQData + 2 * readw(chip->DSPQ + JQS_wHead)));
-
-		wTmp = readw(chip->DSPQ + JQS_wHead) + 1;
-		if (wTmp > readw(chip->DSPQ + JQS_wSize))
-			writew(0, chip->DSPQ + JQS_wHead);
-		else
-			writew(wTmp, chip->DSPQ + JQS_wHead);
+	head = readw(chip->DSPQ + JQS_wHead);
+	tail = readw(chip->DSPQ + JQS_wTail);
+	size = readw(chip->DSPQ + JQS_wSize);
+	if (head > size || tail > size)
+		goto out;
+	while (head != tail) {
+		snd_msnd_eval_dsp_msg(chip, readw(pwDSPQData + 2 * head));
+		if (++head > size)
+			head = 0;
+		writew(head, chip->DSPQ + JQS_wHead);
 	}
+ out:
 	/* Send ack to DSP */
 	inb(chip->io + HP_RXL);
 	return IRQ_HANDLED;

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Thread

[PATCH 4.4 00/31] 4.4.88-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:00 +0200
  [PATCH 4.4 01/31] usb: quirks: add delay init quirk for Corsair Strafe RGB keyboard Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:00 +0200
  [PATCH 4.4 26/31] btrfs: resume qgroup rescan on rw remount Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 15/31] mwifiex: correct channel stat buffer overflows Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 28/31] ALSA: msnd: Optimize / harden DSP and MIDI loops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 05/31] USB: core: Avoid race of async_completed() w/ usbdev_release() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 12/31] rtlwifi: rtl_pci_probe: Fix fail path of _rtl_pci_find_adapter Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 04/31] usb:xhci:Fix regression when ATI chipsets detected Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 09/31] intel_th: pci: Add Cannon Lake PCH-LP support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 06/31] staging/rts5208: fix incorrect shift to extract upper nybble Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 13/31] Bluetooth: Add support of 13d3:3494 RTL8723BE device Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 21/31] drm: adv7511: really enable interrupts for EDID detection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 22/31] drm/bridge: adv7511: Fix mutex deadlock when interrupts are disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 11/31] Input: trackpoint - assume 3 buttons when buttons detection fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 07/31] driver core: bus: Fix a potential double free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 16/31] drm/nouveau/pci/msi: disable MSI on big-endian platforms by default Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 30/31] ARM: 8692/1: mm: abort uaccess retries upon fatal signal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 18/31] cs5536: add support for IDE controller variant Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 03/31] usb: Add device quirk for Logitech HD Pro Webcam C920-C Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  [PATCH 4.4 23/31] drm/bridge: adv7511: Use work_struct to defer hotplug handing to out of irq context Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-12 19:20 +0200
  Re: [PATCH 4.4 00/31] 4.4.88-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-09-13 02:20 +0200
  Re: [PATCH 4.4 00/31] 4.4.88-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-09-13 03:10 +0200
    Re: [PATCH 4.4 00/31] 4.4.88-stable review Kevin Hilman <khilman@baylibre.com> - 2017-09-14 00:00 +0200
      Re: [PATCH 4.4 00/31] 4.4.88-stable review Stephen Boyd <sboyd@codeaurora.org> - 2017-09-19 08:00 +0200
        Re: [PATCH 4.4 00/31] 4.4.88-stable review Mark Brown <broonie@kernel.org> - 2017-09-19 13:20 +0200
  Re: [PATCH 4.4 00/31] 4.4.88-stable review Guenter Roeck <linux@roeck-us.net> - 2017-09-13 16:40 +0200

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