linux.git/sound/core/control.c, branch v3.19

ALSA: snd_ctl_activate_id(): Fix index look-up

2014-11-07T13:25:07+00:00

We want to know the offset for the id that was passed to the function, not
the offset of the first id of the control (which is always 0).

Signed-off-by: Lars-Peter Clausen 
Signed-off-by: Takashi Iwai

ALSA: control: Add missing kerneldoc comments to exported functions

2014-10-30T12:44:34+00:00

A few functions have no proper documentation yet, so let's add them.
Along with it, remove superfluous blank line between the closing brace
and EXPORT_SYMBOL() line.

Signed-off-by: Takashi Iwai

ALSA: control: Allow to pass items zero to snd_ctl_enum_info()

2014-10-20T16:25:41+00:00

Although this is weird, some drivers want to allow empty control
elements intentionally, e.g. the number of items may change depending
on the firmware status.  Let the function simply returning in such a
case.

Signed-off-by: Takashi Iwai

ALSA: control: Warn if too long string is passed to snd_ctl_enum_info()

2014-10-20T16:25:27+00:00

This allows us to catch the bugs in drivers easily.

Signed-off-by: Takashi Iwai

ALSA: control: Define SNDRV_CTL_TLV_OP_* constants

2014-07-15T14:31:01+00:00

Instead of hard-coded magic numbers, define constants for op_flag to
tlv callbacks.

Signed-off-by: Takashi Iwai

ALSA: control: Make sure that id->index does not overflow

2014-06-18T13:13:37+00:00

The ALSA control code expects that the range of assigned indices to a control is
continuous and does not overflow. Currently there are no checks to enforce this.
If a control with a overflowing index range is created that control becomes
effectively inaccessible and unremovable since snd_ctl_find_id() will not be
able to find it. This patch adds a check that makes sure that controls with a
overflowing index range can not be created.

Signed-off-by: Lars-Peter Clausen 
Acked-by: Jaroslav Kysela 
Cc: 
Signed-off-by: Takashi Iwai

ALSA: control: Handle numid overflow

2014-06-18T13:13:23+00:00

Each control gets automatically assigned its numids when the control is created.
The allocation is done by incrementing the numid by the amount of allocated
numids per allocation. This means that excessive creation and destruction of
controls (e.g. via SNDRV_CTL_IOCTL_ELEM_ADD/REMOVE) can cause the id to
eventually overflow. Currently when this happens for the control that caused the
overflow kctl->id.numid + kctl->count will also over flow causing it to be
smaller than kctl->id.numid. Most of the code assumes that this is something
that can not happen, so we need to make sure that it won't happen

Signed-off-by: Lars-Peter Clausen 
Acked-by: Jaroslav Kysela 
Cc: 
Signed-off-by: Takashi Iwai

ALSA: control: Don't access controls outside of protected regions

2014-06-18T13:13:07+00:00

A control that is visible on the card->controls list can be freed at any time.
This means we must not access any of its memory while not holding the
controls_rw_lock. Otherwise we risk a use after free access.

Signed-off-by: Lars-Peter Clausen 
Acked-by: Jaroslav Kysela 
Cc: 
Signed-off-by: Takashi Iwai

ALSA: control: Fix replacing user controls

2014-06-18T13:12:49+00:00

There are two issues with the current implementation for replacing user
controls. The first is that the code does not check if the control is actually a
user control and neither does it check if the control is owned by the process
that tries to remove it. That allows userspace applications to remove arbitrary
controls, which can cause a user after free if a for example a driver does not
expect a control to be removed from under its feed.

The second issue is that on one hand when a control is replaced the
user_ctl_count limit is not checked and on the other hand the user_ctl_count is
increased (even though the number of user controls does not change). This allows
userspace, once the user_ctl_count limit as been reached, to repeatedly replace
a control until user_ctl_count overflows. Once that happens new controls can be
added effectively bypassing the user_ctl_count limit.

Both issues can be fixed by instead of open-coding the removal of the control
that is to be replaced to use snd_ctl_remove_user_ctl(). This function does
proper permission checks as well as decrements user_ctl_count after the control
has been removed.

Note that by using snd_ctl_remove_user_ctl() the check which returns -EBUSY at
beginning of the function if the control already exists is removed. This is not
a problem though since the check is quite useless, because the lock that is
protecting the control list is released between the check and before adding the
new control to the list, which means that it is possible that a different
control with the same settings is added to the list after the check. Luckily
there is another check that is done while holding the lock in snd_ctl_add(), so
we'll rely on that to make sure that the same control is not added twice.

Signed-off-by: Lars-Peter Clausen 
Acked-by: Jaroslav Kysela 
Cc: 
Signed-off-by: Takashi Iwai

ALSA: control: Protect user controls against concurrent access

2014-06-18T13:12:33+00:00

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 
Acked-by: Jaroslav Kysela 
Cc: 
Signed-off-by: Takashi Iwai