From 98482377dc7295d0c70e251925b7cc14aff4c5ac Mon Sep 17 00:00:00 2001 From: Evan Green Date: Mon, 1 Jul 2019 10:30:30 -0700 Subject: ALSA: hda: Fix widget_mutex incomplete protection The widget_mutex was introduced to serialize callers to hda_widget_sysfs_{re}init. However, its protection of the sysfs widget array is incomplete. For example, it is acquired around the call to hda_widget_sysfs_reinit(), which actually creates the new array, but isn't still acquired when codec->num_nodes and codec->start_nid is updated. So the lock ensures one thread sets up the new array at a time, but doesn't ensure which thread's value will end up in codec->num_nodes. If a larger num_nodes wins but a smaller array was set up, the next call to refresh_widgets() will touch free memory as it iterates over codec->num_nodes that aren't there. The widget_lock really protects both the tree as well as codec->num_nodes, start_nid, and end_nid, so make sure it's held across that update. It should also be held during snd_hdac_get_sub_nodes(), so that a very old read from that function doesn't end up clobbering a later update. Fixes: ed180abba7f1 ("ALSA: hda: Fix race between creating and refreshing sysfs entries") Signed-off-by: Evan Green Signed-off-by: Takashi Iwai --- sound/hda/hdac_device.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) (limited to 'sound/hda') diff --git a/sound/hda/hdac_device.c b/sound/hda/hdac_device.c index 4769f4c03e14..11050bfd8068 100644 --- a/sound/hda/hdac_device.c +++ b/sound/hda/hdac_device.c @@ -399,27 +399,33 @@ static void setup_fg_nodes(struct hdac_device *codec) int snd_hdac_refresh_widgets(struct hdac_device *codec, bool sysfs) { hda_nid_t start_nid; - int nums, err; + int nums, err = 0; + /* + * Serialize against multiple threads trying to update the sysfs + * widgets array. + */ + mutex_lock(&codec->widget_lock); nums = snd_hdac_get_sub_nodes(codec, codec->afg, &start_nid); if (!start_nid || nums <= 0 || nums >= 0xff) { dev_err(&codec->dev, "cannot read sub nodes for FG 0x%02x\n", codec->afg); - return -EINVAL; + err = -EINVAL; + goto unlock; } if (sysfs) { - mutex_lock(&codec->widget_lock); err = hda_widget_sysfs_reinit(codec, start_nid, nums); - mutex_unlock(&codec->widget_lock); if (err < 0) - return err; + goto unlock; } codec->num_nodes = nums; codec->start_nid = start_nid; codec->end_nid = start_nid + nums; - return 0; +unlock: + mutex_unlock(&codec->widget_lock); + return err; } EXPORT_SYMBOL_GPL(snd_hdac_refresh_widgets); -- cgit v1.2.3 From 774a075ab5140bb4504e6026bf327021926c3e65 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 3 Jul 2019 14:35:12 +0200 Subject: ALSA: hda: Simplify snd_hdac_refresh_widgets() Along with the recent fix for the races of snd_hdac_refresh_widgets() it turned out that the instantiation of widgets sysfs at snd_hdac_sysfs_reinit() could cause a race. The race itself was already covered later by extending the mutex protection range, the commit 98482377dc72 ("ALSA: hda: Fix widget_mutex incomplete protection"), but this also indicated that the call of *_reinit() is basically superfluous, as the widgets shall be created sooner or later from snd_hdac_device_register(). This patch removes the redundant call of snd_hdac_sysfs_reinit() at first. By this removal, the sysfs argument itself in snd_hdac_refresh_widgets() becomes superfluous, too, because the only case sysfs=false is always with codec->widgets=NULL. So, we drop this redundant argument as well. Signed-off-by: Takashi Iwai --- sound/hda/hdac_device.c | 13 +++++-------- sound/hda/hdac_sysfs.c | 2 +- 2 files changed, 6 insertions(+), 9 deletions(-) (limited to 'sound/hda') diff --git a/sound/hda/hdac_device.c b/sound/hda/hdac_device.c index 11050bfd8068..a265c1d68876 100644 --- a/sound/hda/hdac_device.c +++ b/sound/hda/hdac_device.c @@ -89,7 +89,7 @@ int snd_hdac_device_init(struct hdac_device *codec, struct hdac_bus *bus, fg = codec->afg ? codec->afg : codec->mfg; - err = snd_hdac_refresh_widgets(codec, false); + err = snd_hdac_refresh_widgets(codec); if (err < 0) goto error; @@ -394,9 +394,8 @@ static void setup_fg_nodes(struct hdac_device *codec) /** * snd_hdac_refresh_widgets - Reset the widget start/end nodes * @codec: the codec object - * @sysfs: re-initialize sysfs tree, too */ -int snd_hdac_refresh_widgets(struct hdac_device *codec, bool sysfs) +int snd_hdac_refresh_widgets(struct hdac_device *codec) { hda_nid_t start_nid; int nums, err = 0; @@ -414,11 +413,9 @@ int snd_hdac_refresh_widgets(struct hdac_device *codec, bool sysfs) goto unlock; } - if (sysfs) { - err = hda_widget_sysfs_reinit(codec, start_nid, nums); - if (err < 0) - goto unlock; - } + err = hda_widget_sysfs_reinit(codec, start_nid, nums); + if (err < 0) + goto unlock; codec->num_nodes = nums; codec->start_nid = start_nid; diff --git a/sound/hda/hdac_sysfs.c b/sound/hda/hdac_sysfs.c index 909d5ef1179c..e56e83325903 100644 --- a/sound/hda/hdac_sysfs.c +++ b/sound/hda/hdac_sysfs.c @@ -428,7 +428,7 @@ int hda_widget_sysfs_reinit(struct hdac_device *codec, int i; if (!codec->widgets) - return hda_widget_sysfs_init(codec); + return 0; tree = kmemdup(codec->widgets, sizeof(*tree), GFP_KERNEL); if (!tree) -- cgit v1.2.3