ALSA: hda - Fix widget sysfs tree corruption after refresh

When snd_hdac_refresh_widget_sysfs() is called before the first
hda_widget_sysfs_init(), the next call overrides and eventually
fails.  This results in unexpected Oops, something like:
  BUG: unable to handle kernel NULL pointer dereference at 00000000000000c8
  IP: [<ffffffff8180e2a3>] hdmi_chmap_ctl_info+0x23/0x40

The fix is to add a check of the existing sysfs tree.  Also, for more
safety, this patch adds the checks of device_is_registered() in
snd-hdac_refresh_wdiget_sysfs(), too.

Fixes: fa4f18b4f402 ('ALSA: hda - Refresh widgets sysfs at probing Haswell+ HDMI codecs')
Bugizlla: https://bugzilla.kernel.org/show_bug.cgi?id=103431
Reported-by: Andreas Reis <andreas.reis@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 11 insertions, 6 deletions

diff --git a/sound/hda/hdac_device.c b/sound/hda/hdac_device.c
index aa6d6cec2380..db96042a497f 100644
--- a/sound/hda/hdac_device.c
+++ b/sound/hda/hdac_device.c
@@ -384,18 +384,20 @@ int snd_hdac_refresh_widget_sysfs(struct hdac_device *codec)
 {
         int ret;
 
-        hda_widget_sysfs_exit(codec);
+        if (device_is_registered(&codec->dev))
+                hda_widget_sysfs_exit(codec);
         ret = snd_hdac_refresh_widgets(codec);
         if (ret) {
                 dev_err(&codec->dev, "failed to refresh widget: %d\n", ret);
                 return ret;
         }
-        ret = hda_widget_sysfs_init(codec);
-        if (ret) {
-                dev_err(&codec->dev, "failed to init sysfs: %d\n", ret);
-                return ret;
+        if (device_is_registered(&codec->dev)) {
+                ret = hda_widget_sysfs_init(codec);
+                if (ret) {
+                        dev_err(&codec->dev, "failed to init sysfs: %d\n", ret);
+                        return ret;
+                }
         }
-
         return ret;
 }
 EXPORT_SYMBOL_GPL(snd_hdac_refresh_widget_sysfs);
diff --git a/sound/hda/hdac_sysfs.c b/sound/hda/hdac_sysfs.c
index 089b35f6f108..c71142dea98a 100644
--- a/sound/hda/hdac_sysfs.c
+++ b/sound/hda/hdac_sysfs.c
@@ -390,6 +390,9 @@ int hda_widget_sysfs_init(struct hdac_device *codec)
 {
         int err;
 
+        if (codec->widgets)
+                return 0; /* already created */
+
         err = widget_tree_create(codec);
         if (err < 0) {
                 widget_tree_free(codec);