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authorLars-Peter Clausen <lars@metafoo.de>2014-06-18 15:32:31 +0400
committerTakashi Iwai <tiwai@suse.de>2014-06-18 17:12:33 +0400
commit07f4d9d74a04aa7c72c5dae0ef97565f28f17b92 (patch)
tree65d9ee5f96dacb86a33d3a8cd786e876563d93ac /sound/core/control.c
parent7171511eaec5bf23fb06078f59784a3a0626b38f (diff)
downloadlinux-07f4d9d74a04aa7c72c5dae0ef97565f28f17b92.tar.xz
ALSA: control: Protect user controls against concurrent access
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> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/control.c')
-rw-r--r--sound/core/control.c31
1 files changed, 25 insertions, 6 deletions
diff --git a/sound/core/control.c b/sound/core/control.c
index f038f5afafe2..00ab034f5fcb 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -991,6 +991,7 @@ 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 */
@@ -1034,7 +1035,9 @@ 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;
}
@@ -1043,10 +1046,12 @@ 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;
}
@@ -1066,19 +1071,32 @@ 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;
}
@@ -1210,6 +1228,7 @@ 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);