From c637fa151259c0f74665fde7cba5b7eac1417ae5 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Sat, 16 May 2020 08:25:56 +0200
Subject: [PATCH] ALSA: hda: Fix potential race in unsol event handler
Git-commit: c637fa151259c0f74665fde7cba5b7eac1417ae5
Patch-mainline: v5.8-rc1
References: git-fixes

The unsol event handling code has a loop retrieving the read/write
indices and the arrays without locking while the append to the array
may happen concurrently.  This may lead to some inconsistency.
Although there hasn't been any proof of this bad results, it's still
safer to protect the racy accesses.

This patch adds the spinlock protection around the unsol handling loop
for addressing it.  Here we take bus->reg_lock as the writer side
snd_hdac_bus_queue_event() is also protected by that lock.

Link: https://lore.kernel.org/r/20200516062556.30951-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/hda/hdac_bus.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/hda/hdac_bus.c b/sound/hda/hdac_bus.c
index 3fe62be1cbcc..dee04792ca86 100644
--- a/sound/hda/hdac_bus.c
+++ b/sound/hda/hdac_bus.c
@@ -162,6 +162,7 @@ static void snd_hdac_bus_process_unsol_events(struct work_struct *work)
 	struct hdac_driver *drv;
 	unsigned int rp, caddr, res;
 
+	spin_lock_irq(&bus->reg_lock);
 	while (bus->unsol_rp != bus->unsol_wp) {
 		rp = (bus->unsol_rp + 1) % HDA_UNSOL_QUEUE_SIZE;
 		bus->unsol_rp = rp;
@@ -173,10 +174,13 @@ static void snd_hdac_bus_process_unsol_events(struct work_struct *work)
 		codec = bus->caddr_tbl[caddr & 0x0f];
 		if (!codec || !codec->dev.driver)
 			continue;
+		spin_unlock_irq(&bus->reg_lock);
 		drv = drv_to_hdac_driver(codec->dev.driver);
 		if (drv->unsol_event)
 			drv->unsol_event(codec, res);
+		spin_lock_irq(&bus->reg_lock);
 	}
+	spin_unlock_irq(&bus->reg_lock);
 }
 
 /**
-- 
2.26.2