From c1f0616124c455c5c762b6f123e40bba5df759e6 Mon Sep 17 00:00:00 2001

From: Takashi Iwai <tiwai@suse.de>

Date: Sun, 16 May 2021 18:17:55 +0200

Subject: [PATCH] ALSA: intel8x0: Don't update period unless prepared

Git-commit: c1f0616124c455c5c762b6f123e40bba5df759e6

Patch-mainline: v5.13-rc3

References: git-fixes

The interrupt handler of intel8x0 calls snd_intel8x0_update() whenever

the hardware sets the corresponding status bit for each stream.  This

works fine for most cases as long as the hardware behaves properly.

But when the hardware gives a wrong bit set, this leads to a zero-

division Oops, and reportedly, this seems what happened on a VM.

For fixing the crash, this patch adds a internal flag indicating that

the stream is ready to be updated, and check it (as well as the flag

being in suspended) to ignore such spurious update.

Cc: <stable@vger.kernel.org>

Reported-and-tested-by: Sergey Senozhatsky <senozhatsky@chromium.org>

Link: https://lore.kernel.org/r/s5h5yzi7uh0.wl-tiwai@suse.de

Signed-off-by: Takashi Iwai <tiwai@suse.de>

---

 sound/pci/intel8x0.c |    7 +++++++

 1 file changed, 7 insertions(+)

--- a/sound/pci/intel8x0.c

+++ b/sound/pci/intel8x0.c

@@ -354,6 +354,7 @@ struct ichdev {

 	unsigned int ali_slot;			/* ALI DMA slot */

 	struct ac97_pcm *pcm;

 	int pcm_open_flag;

+	unsigned int prepared:1;

 	unsigned int suspended: 1;

 };

@@ -714,6 +715,9 @@ static inline void snd_intel8x0_update(s

 	int status, civ, i, step;

 	int ack = 0;

+	if (!ichdev->prepared || ichdev->suspended)

+		return;

+

 	spin_lock_irqsave(&chip->reg_lock, flags);

 	status = igetbyte(chip, port + ichdev->roff_sr);

 	civ = igetbyte(chip, port + ICH_REG_OFF_CIV);

@@ -907,6 +911,7 @@ static int snd_intel8x0_hw_params(struct

 	if (ichdev->pcm_open_flag) {

 		snd_ac97_pcm_close(ichdev->pcm);

 		ichdev->pcm_open_flag = 0;

+		ichdev->prepared = 0;

 	}

 	err = snd_ac97_pcm_open(ichdev->pcm, params_rate(hw_params),

 				params_channels(hw_params),

@@ -928,6 +933,7 @@ static int snd_intel8x0_hw_free(struct s

 	if (ichdev->pcm_open_flag) {

 		snd_ac97_pcm_close(ichdev->pcm);

 		ichdev->pcm_open_flag = 0;

+		ichdev->prepared = 0;

 	}

 	return snd_pcm_lib_free_pages(substream);

 }

@@ -1002,6 +1008,7 @@ static int snd_intel8x0_pcm_prepare(stru

 			ichdev->pos_shift = (runtime->sample_bits > 16) ? 2 : 1;

 	}

 	snd_intel8x0_setup_periods(chip, ichdev);

+	ichdev->prepared = 1;

 	return 0;

 }