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authorLars-Peter Clausen <lars@metafoo.de>2014-06-18 13:32:31 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-06-26 15:10:29 -0400
commite4036860a70f956370a18ef06a19fa10a25990d2 (patch)
treedc6caa66184413a780eaa1fb125ab56634f47b5a
parent118264918814946dd5ce4c87f1c643f2d20e70f6 (diff)
downloadlinux-linaro-stable-e4036860a70f956370a18ef06a19fa10a25990d2.tar.gz
ALSA: control: Protect user controls against concurrent access
commit 07f4d9d74a04aa7c72c5dae0ef97565f28f17b92 upstream. The user-control put and get handlers as well as the tlv do not protect against concurrent access from multiple threads. Since the state of the control is not updated atomically it is possible that either two write operations or a write and a read operation race against each other. Both can lead to arbitrary memory disclosure. This patch introduces a new lock that protects user-controls from concurrent access. Since applications typically access controls sequentially than in parallel a single lock per card should be fine. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Acked-by: Jaroslav Kysela <perex@perex.cz> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--include/sound/core.h2
-rw-r--r--sound/core/control.c31
-rw-r--r--sound/core/init.c1
3 files changed, 28 insertions, 6 deletions
diff --git a/include/sound/core.h b/include/sound/core.h
index 93896ad1fcdd..8d29d28d3696 100644
--- a/include/sound/core.h
+++ b/include/sound/core.h
@@ -120,6 +120,8 @@ struct snd_card {
int user_ctl_count; /* count of all user controls */
struct list_head controls; /* all controls for this card */
struct list_head ctl_files; /* active control files */
+ struct mutex user_ctl_lock; /* protects user controls against
+ concurrent access */
struct snd_info_entry *proc_root; /* root for soundcard specific files */
struct snd_info_entry *proc_id; /* the card id */
diff --git a/sound/core/control.c b/sound/core/control.c
index daa4fc8872f3..5746f769d5a6 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -988,6 +988,7 @@ static int snd_ctl_elem_unlock(struct snd_ctl_file *file,
struct user_element {
struct snd_ctl_elem_info info;
+ struct snd_card *card;
void *elem_data; /* element data */
unsigned long elem_data_size; /* size of element data in bytes */
void *tlv_data; /* TLV data */
@@ -1031,7 +1032,9 @@ static int snd_ctl_elem_user_get(struct snd_kcontrol *kcontrol,
{
struct user_element *ue = kcontrol->private_data;
+ mutex_lock(&ue->card->user_ctl_lock);
memcpy(&ucontrol->value, ue->elem_data, ue->elem_data_size);
+ mutex_unlock(&ue->card->user_ctl_lock);
return 0;
}
@@ -1040,10 +1043,12 @@ static int snd_ctl_elem_user_put(struct snd_kcontrol *kcontrol,
{
int change;
struct user_element *ue = kcontrol->private_data;
-
+
+ mutex_lock(&ue->card->user_ctl_lock);
change = memcmp(&ucontrol->value, ue->elem_data, ue->elem_data_size) != 0;
if (change)
memcpy(ue->elem_data, &ucontrol->value, ue->elem_data_size);
+ mutex_unlock(&ue->card->user_ctl_lock);
return change;
}
@@ -1063,19 +1068,32 @@ static int snd_ctl_elem_user_tlv(struct snd_kcontrol *kcontrol,
new_data = memdup_user(tlv, size);
if (IS_ERR(new_data))
return PTR_ERR(new_data);
+ mutex_lock(&ue->card->user_ctl_lock);
change = ue->tlv_data_size != size;
if (!change)
change = memcmp(ue->tlv_data, new_data, size);
kfree(ue->tlv_data);
ue->tlv_data = new_data;
ue->tlv_data_size = size;
+ mutex_unlock(&ue->card->user_ctl_lock);
} else {
- if (! ue->tlv_data_size || ! ue->tlv_data)
- return -ENXIO;
- if (size < ue->tlv_data_size)
- return -ENOSPC;
+ int ret = 0;
+
+ mutex_lock(&ue->card->user_ctl_lock);
+ if (!ue->tlv_data_size || !ue->tlv_data) {
+ ret = -ENXIO;
+ goto err_unlock;
+ }
+ if (size < ue->tlv_data_size) {
+ ret = -ENOSPC;
+ goto err_unlock;
+ }
if (copy_to_user(tlv, ue->tlv_data, ue->tlv_data_size))
- return -EFAULT;
+ ret = -EFAULT;
+err_unlock:
+ mutex_unlock(&ue->card->user_ctl_lock);
+ if (ret)
+ return ret;
}
return change;
}
@@ -1207,6 +1225,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file,
ue = kzalloc(sizeof(struct user_element) + private_size, GFP_KERNEL);
if (ue == NULL)
return -ENOMEM;
+ ue->card = card;
ue->info = *info;
ue->info.access = 0;
ue->elem_data = (char *)ue + sizeof(*ue);
diff --git a/sound/core/init.c b/sound/core/init.c
index 7b012d15c2cf..41020d7395f3 100644
--- a/sound/core/init.c
+++ b/sound/core/init.c
@@ -208,6 +208,7 @@ int snd_card_create(int idx, const char *xid,
INIT_LIST_HEAD(&card->devices);
init_rwsem(&card->controls_rwsem);
rwlock_init(&card->ctl_files_rwlock);
+ mutex_init(&card->user_ctl_lock);
INIT_LIST_HEAD(&card->controls);
INIT_LIST_HEAD(&card->ctl_files);
spin_lock_init(&card->files_lock);