On Sat, 23 Jan 2021 04:10:25 +0100, Takashi Sakamoto wrote:

Hi,

On Fri, Jan 22, 2021 at 03:04:56PM +0100, Takashi Iwai wrote:

...

On Fri, 22 Jan 2021 09:20:32 +0100, Takashi Sakamoto wrote:

...

ALSA control core allows usespace application to register control element set by call of ioctl(2) with SNDRV_CTL_IOCTL_ELEM_ADD request. The added control elements are called as 'user-defined'. Currently sound card has limitation on the number of the user-defined control element set up to 32.

The limitation is inconvenient to drivers in ALSA firewire stack since the drivers expect userspace applications to implement function to control device functionalities such as mixing and routing. As the userspace application, snd-firewire-ctl-services project starts: https://github.com/alsa-project/snd-firewire-ctl-services/

The project supports many devices supported by ALSA firewire stack. The limitation is mostly good since routing and mixing controls can be represented by control element set, which includes multiple control element with the same parameters. Nevertheless, it's actually inconvenient to device which has many varied functionalities. For example, plugin effect such as channel strip and reverb has many parameters. For the case, many control elements are required to configure the parameters and control element set cannot aggregates them for the parameters. At present, the implementations for below models requires more control element sets than 32:

• snd-bebob-ctl-service
  • Apogee Ensemble (31 sets for 34 elements)
• snd-dice-ctl-service
  • TC Electronic Konnekt 24d (78 sets for 94 elements)
  • TC Electronic Studio Konnekt 48 (98 sets for 114 elements)
  • TC Electronic Konnekt Live (88 sets for 104 elements)
  • TC Electronic Impact Twin (70 sets for 86 elements)
  • Focusrite Liquid Saffire 56 (37 sets for 52 elements)

This commit expands the limitation according to requirement from the above applications. As a result, userspace applications can add control element sets up to 150 per sound card. It results in 154,200 user-defined control elements as maximum since one control element set can include 1028 control elements.

Thinking of this change again after reading your description, I find that a more flexible and safer approach would be to limit the number of total elements. That is, count the number of items in each element, and set the max to (32 * MAX_CONTROL_COUNT). This will keep the same max as the current implementation can achieve, while it allows more elements as long as they contain lower number of items.

So, something like below (totally untested).

thanks,

Takashi

--- a/sound/core/control.c +++ b/sound/core/control.c @@ -18,10 +18,11 @@ #include <sound/info.h> #include <sound/control.h>

-/* max number of user-defined controls */ -#define MAX_USER_CONTROLS 32 #define MAX_CONTROL_COUNT 1028

+/* max number of user-defined controls */ +#define MAX_USER_CONTROLS (32 * MAX_CONTROL_COUNT)

struct snd_kctl_ioctl { struct list_head list; /* list of all ioctls */ snd_kctl_ioctl_func_t fioctl; @@ -520,6 +521,7 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file, struct snd_card *card = file->card; struct snd_kcontrol *kctl; int idx, ret;

• int count;

  down_write(&card->controls_rwsem); kctl = snd_ctl_find_id(card, id);

@@ -536,10 +538,11 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file, ret = -EBUSY; goto error; }

• count = kctl->count; ret = snd_ctl_remove(card, kctl); if (ret < 0) goto error;

• card->user_ctl_count--;

• card->user_ctl_count -= count;

error: up_write(&card->controls_rwsem); return ret; @@ -1435,18 +1438,18 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, return err; }

• /* Check the number of elements for this userspace control. */
• count = info->owner;
• if (count == 0)

• count = 1;
  

• /*
  • The number of userspace controls are counted control by control,
  • not element by element.
  */

• if (card->user_ctl_count + 1 > MAX_USER_CONTROLS)

• if (card->user_ctl_count + count > MAX_USER_CONTROLS) return -ENOMEM;

• /* Check the number of elements for this userspace control. */
• count = info->owner;
• if (count == 0)

• count = 1;
  

• /* Arrange access permissions if needed. */ access = info->access; if (access == 0)

@@ -1535,7 +1538,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, * which locks the element. */

• card->user_ctl_count++;

• card->user_ctl_count += count;

  unlock: up_write(&card->controls_rwsem);

I have no objection to any change as long as it allows the service programs to add control elements enough for target device. However, it's unclear what is flexible and safe in the above patch.

When adding user-defined control element set, some objects are allocated for below structures with some variable-length members:

• struct snd_kcontrol (in include/sound/control.h)
• struct user_element (in sound/core/control.h)

Current implementation is to avoid too much allocation for the above against userspace applications with bugs or mis-programming. It's reasonable to limit the allocation according to count of added control element set for the purpose.

On the other hand, when counting the number of added control element for the limitation, the above becomes loose. In the worst case, the patch allows 32,896 sets to be allocated and against comments in my previous patch.

OK, my previous patch was too simplified (I forgot to take the private_data into account), but the point is that what we want is to cap the worst case memory consumption.

If I calculate correctly, user_element is 320 bytes, and the value is up to 512 bytes for each item, and snd_kcontrol is 144 bytes, and snd_kcontrol_volatile is 16 bytes per item. And each element may contain 1028 items. So, the worst case scenario of the memory consumption is: (320 + 512*1028 + 144 + 16*1024) * 32 = 17383936 That is, currently we allow 16MB at most.

By increasing MAX_USER_CONTROLS to 150, it'll become 77MB.

And, think what if you'd need to increase more in future, e.g. 512 elements. The max consumption also increases linearly.

OTOH, imagine that we cap the memory consumption to 16MB instead of limiting only the MAX_USER_CONTROLS. This lets user still allow to allocate more elements with smaller number of items (that is the common use case). In this way, we don't take a risk of higher memory consumption while user can deploy the user elements more flexibly.

Takashi

Hi,

On Sat, Jan 23, 2021 at 10:10:20AM +0100, Takashi Iwai wrote:

On Sat, 23 Jan 2021 04:10:25 +0100, Takashi Sakamoto wrote:

...

Hi,

On Fri, Jan 22, 2021 at 03:04:56PM +0100, Takashi Iwai wrote:

...

On Fri, 22 Jan 2021 09:20:32 +0100, Takashi Sakamoto wrote:

...

ALSA control core allows usespace application to register control element set by call of ioctl(2) with SNDRV_CTL_IOCTL_ELEM_ADD request. The added control elements are called as 'user-defined'. Currently sound card has limitation on the number of the user-defined control element set up to 32.

The limitation is inconvenient to drivers in ALSA firewire stack since the drivers expect userspace applications to implement function to control device functionalities such as mixing and routing. As the userspace application, snd-firewire-ctl-services project starts: https://github.com/alsa-project/snd-firewire-ctl-services/

The project supports many devices supported by ALSA firewire stack. The limitation is mostly good since routing and mixing controls can be represented by control element set, which includes multiple control element with the same parameters. Nevertheless, it's actually inconvenient to device which has many varied functionalities. For example, plugin effect such as channel strip and reverb has many parameters. For the case, many control elements are required to configure the parameters and control element set cannot aggregates them for the parameters. At present, the implementations for below models requires more control element sets than 32:

• snd-bebob-ctl-service
  • Apogee Ensemble (31 sets for 34 elements)
• snd-dice-ctl-service
  • TC Electronic Konnekt 24d (78 sets for 94 elements)
  • TC Electronic Studio Konnekt 48 (98 sets for 114 elements)
  • TC Electronic Konnekt Live (88 sets for 104 elements)
  • TC Electronic Impact Twin (70 sets for 86 elements)
  • Focusrite Liquid Saffire 56 (37 sets for 52 elements)

This commit expands the limitation according to requirement from the above applications. As a result, userspace applications can add control element sets up to 150 per sound card. It results in 154,200 user-defined control elements as maximum since one control element set can include 1028 control elements.

Thinking of this change again after reading your description, I find that a more flexible and safer approach would be to limit the number of total elements. That is, count the number of items in each element, and set the max to (32 * MAX_CONTROL_COUNT). This will keep the same max as the current implementation can achieve, while it allows more elements as long as they contain lower number of items.

So, something like below (totally untested).

thanks,

Takashi

--- a/sound/core/control.c +++ b/sound/core/control.c @@ -18,10 +18,11 @@ #include <sound/info.h> #include <sound/control.h>

-/* max number of user-defined controls */ -#define MAX_USER_CONTROLS 32 #define MAX_CONTROL_COUNT 1028

+/* max number of user-defined controls */ +#define MAX_USER_CONTROLS (32 * MAX_CONTROL_COUNT)

struct snd_kctl_ioctl { struct list_head list; /* list of all ioctls */ snd_kctl_ioctl_func_t fioctl; @@ -520,6 +521,7 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file, struct snd_card *card = file->card; struct snd_kcontrol *kctl; int idx, ret;

• int count;

  down_write(&card->controls_rwsem); kctl = snd_ctl_find_id(card, id);

@@ -536,10 +538,11 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file, ret = -EBUSY; goto error; }

• count = kctl->count; ret = snd_ctl_remove(card, kctl); if (ret < 0) goto error;

• card->user_ctl_count--;

• card->user_ctl_count -= count;

error: up_write(&card->controls_rwsem); return ret; @@ -1435,18 +1438,18 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, return err; }

• /* Check the number of elements for this userspace control. */
• count = info->owner;
• if (count == 0)

• count = 1;
  

• /*
  • The number of userspace controls are counted control by control,
  • not element by element.
  */

• if (card->user_ctl_count + 1 > MAX_USER_CONTROLS)

• if (card->user_ctl_count + count > MAX_USER_CONTROLS) return -ENOMEM;

• /* Check the number of elements for this userspace control. */
• count = info->owner;
• if (count == 0)

• count = 1;
  

• /* Arrange access permissions if needed. */ access = info->access; if (access == 0)

@@ -1535,7 +1538,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, * which locks the element. */

• card->user_ctl_count++;

• card->user_ctl_count += count;

  unlock: up_write(&card->controls_rwsem);

I have no objection to any change as long as it allows the service programs to add control elements enough for target device. However, it's unclear what is flexible and safe in the above patch.

When adding user-defined control element set, some objects are allocated for below structures with some variable-length members:

• struct snd_kcontrol (in include/sound/control.h)
• struct user_element (in sound/core/control.h)

Current implementation is to avoid too much allocation for the above against userspace applications with bugs or mis-programming. It's reasonable to limit the allocation according to count of added control element set for the purpose.

On the other hand, when counting the number of added control element for the limitation, the above becomes loose. In the worst case, the patch allows 32,896 sets to be allocated and against comments in my previous patch.

OK, my previous patch was too simplified (I forgot to take the private_data into account), but the point is that what we want is to cap the worst case memory consumption.

If I calculate correctly, user_element is 320 bytes, and the value is up to 512 bytes for each item, and snd_kcontrol is 144 bytes, and snd_kcontrol_volatile is 16 bytes per item. And each element may contain 1028 items. So, the worst case scenario of the memory consumption is: (320 + 512*1028 + 144 + 16*1024) * 32 = 17383936 That is, currently we allow 16MB at most.

By increasing MAX_USER_CONTROLS to 150, it'll become 77MB.

And, think what if you'd need to increase more in future, e.g. 512 elements. The max consumption also increases linearly.

OTOH, imagine that we cap the memory consumption to 16MB instead of limiting only the MAX_USER_CONTROLS. This lets user still allow to allocate more elements with smaller number of items (that is the common use case). In this way, we don't take a risk of higher memory consumption while user can deploy the user elements more flexibly.

The memory object for data of Type-Length-Value style is underestimate in your calculation for the worst case. For user-defined control element set, the size is (1024 * 128) per control element set[1].

Of cource, it's possible to judge that usual userspace application don't use data of Type-Length-Value style so much. However, we are assuming the worst case now.

``` Objects linearly increased according to the number of user-defined control element sets: * struct snd_kcontrol (144 bytes) * struct user_element (320 bytes) * data of TLV ((1024 * 128) bytes as maximum)

Objects linearly increased according to the number of control elements: * data of values (max. 1024 bytes in System V ABI with LP64 data type) * data of snd_kcontrol_volatile (16 bytes)

Memory consumption under current limitation: (144 + 320 + 1024 * 128) * 32 + (1024 + 16) * 1028 = 5,278,272

Scenario for the worst case when appying the patch: * adding 32,896 control element sets * for elements: (1024 + 16) * 1028 * 32 = 34,211,840 * for element sets: (144 + 320 + 1024 * 128) * 32896 = 4,327,008,256

Scenario for the worst case when applying my patch: * adding 150 control element sets * for elements: (1024 + 16) * 1028 * 150 = 160,368,000 * for element sets: (144 + 320 + 1024 * 128) * 150 = 19,730,400 ```

[1] https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/tree/sound/c...

Regards

Takashi Sakamoto

Hi,

On Sun, Jan 24, 2021 at 08:49:11AM +0100, Takashi Iwai wrote:

On Sun, 24 Jan 2021 06:52:25 +0100, Takashi Sakamoto wrote:

...

Hi,

On Sat, Jan 23, 2021 at 10:10:20AM +0100, Takashi Iwai wrote:

...

On Sat, 23 Jan 2021 04:10:25 +0100, Takashi Sakamoto wrote:

...

Hi,

On Fri, Jan 22, 2021 at 03:04:56PM +0100, Takashi Iwai wrote:

...

On Fri, 22 Jan 2021 09:20:32 +0100, Takashi Sakamoto wrote:

...

ALSA control core allows usespace application to register control element set by call of ioctl(2) with SNDRV_CTL_IOCTL_ELEM_ADD request. The added control elements are called as 'user-defined'. Currently sound card has limitation on the number of the user-defined control element set up to 32.

The limitation is inconvenient to drivers in ALSA firewire stack since the drivers expect userspace applications to implement function to control device functionalities such as mixing and routing. As the userspace application, snd-firewire-ctl-services project starts: https://github.com/alsa-project/snd-firewire-ctl-services/

The project supports many devices supported by ALSA firewire stack. The limitation is mostly good since routing and mixing controls can be represented by control element set, which includes multiple control element with the same parameters. Nevertheless, it's actually inconvenient to device which has many varied functionalities. For example, plugin effect such as channel strip and reverb has many parameters. For the case, many control elements are required to configure the parameters and control element set cannot aggregates them for the parameters. At present, the implementations for below models requires more control element sets than 32:

• snd-bebob-ctl-service
  • Apogee Ensemble (31 sets for 34 elements)
• snd-dice-ctl-service
  • TC Electronic Konnekt 24d (78 sets for 94 elements)
  • TC Electronic Studio Konnekt 48 (98 sets for 114 elements)
  • TC Electronic Konnekt Live (88 sets for 104 elements)
  • TC Electronic Impact Twin (70 sets for 86 elements)
  • Focusrite Liquid Saffire 56 (37 sets for 52 elements)

This commit expands the limitation according to requirement from the above applications. As a result, userspace applications can add control element sets up to 150 per sound card. It results in 154,200 user-defined control elements as maximum since one control element set can include 1028 control elements.

Thinking of this change again after reading your description, I find that a more flexible and safer approach would be to limit the number of total elements. That is, count the number of items in each element, and set the max to (32 * MAX_CONTROL_COUNT). This will keep the same max as the current implementation can achieve, while it allows more elements as long as they contain lower number of items.

So, something like below (totally untested).

thanks,

Takashi

--- a/sound/core/control.c +++ b/sound/core/control.c @@ -18,10 +18,11 @@ #include <sound/info.h> #include <sound/control.h>

-/* max number of user-defined controls */ -#define MAX_USER_CONTROLS 32 #define MAX_CONTROL_COUNT 1028

+/* max number of user-defined controls */ +#define MAX_USER_CONTROLS (32 * MAX_CONTROL_COUNT)

struct snd_kctl_ioctl { struct list_head list; /* list of all ioctls */ snd_kctl_ioctl_func_t fioctl; @@ -520,6 +521,7 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file, struct snd_card *card = file->card; struct snd_kcontrol *kctl; int idx, ret;

• int count;

  down_write(&card->controls_rwsem); kctl = snd_ctl_find_id(card, id);

@@ -536,10 +538,11 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file, ret = -EBUSY; goto error; }

• count = kctl->count; ret = snd_ctl_remove(card, kctl); if (ret < 0) goto error;

• card->user_ctl_count--;

• card->user_ctl_count -= count;

error: up_write(&card->controls_rwsem); return ret; @@ -1435,18 +1438,18 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, return err; }

• /* Check the number of elements for this userspace control. */
• count = info->owner;
• if (count == 0)

• count = 1;
  

• /*
  • The number of userspace controls are counted control by control,
  • not element by element.
  */

• if (card->user_ctl_count + 1 > MAX_USER_CONTROLS)

• if (card->user_ctl_count + count > MAX_USER_CONTROLS) return -ENOMEM;

• /* Check the number of elements for this userspace control. */
• count = info->owner;
• if (count == 0)

• count = 1;
  

• /* Arrange access permissions if needed. */ access = info->access; if (access == 0)

@@ -1535,7 +1538,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, * which locks the element. */

• card->user_ctl_count++;

• card->user_ctl_count += count;

  unlock: up_write(&card->controls_rwsem);

I have no objection to any change as long as it allows the service programs to add control elements enough for target device. However, it's unclear what is flexible and safe in the above patch.

When adding user-defined control element set, some objects are allocated for below structures with some variable-length members:

• struct snd_kcontrol (in include/sound/control.h)
• struct user_element (in sound/core/control.h)

Current implementation is to avoid too much allocation for the above against userspace applications with bugs or mis-programming. It's reasonable to limit the allocation according to count of added control element set for the purpose.

On the other hand, when counting the number of added control element for the limitation, the above becomes loose. In the worst case, the patch allows 32,896 sets to be allocated and against comments in my previous patch.

OK, my previous patch was too simplified (I forgot to take the private_data into account), but the point is that what we want is to cap the worst case memory consumption.

If I calculate correctly, user_element is 320 bytes, and the value is up to 512 bytes for each item, and snd_kcontrol is 144 bytes, and snd_kcontrol_volatile is 16 bytes per item. And each element may contain 1028 items. So, the worst case scenario of the memory consumption is: (320 + 512*1028 + 144 + 16*1024) * 32 = 17383936 That is, currently we allow 16MB at most.

By increasing MAX_USER_CONTROLS to 150, it'll become 77MB.

And, think what if you'd need to increase more in future, e.g. 512 elements. The max consumption also increases linearly.

OTOH, imagine that we cap the memory consumption to 16MB instead of limiting only the MAX_USER_CONTROLS. This lets user still allow to allocate more elements with smaller number of items (that is the common use case). In this way, we don't take a risk of higher memory consumption while user can deploy the user elements more flexibly.

The memory object for data of Type-Length-Value style is underestimate in your calculation for the worst case. For user-defined control element set, the size is (1024 * 128) per control element set[1].

Of cource, it's possible to judge that usual userspace application don't use data of Type-Length-Value style so much. However, we are assuming the worst case now.

Right, that should be taken into account.

...

Objects linearly increased according to the number of user-defined control
element sets:
 * struct snd_kcontrol (144 bytes)
 * struct user_element (320 bytes)
 * data of TLV ((1024 * 128) bytes as maximum)

Objects linearly increased according to the number of control elements:
 * data of values (max. 1024 bytes in System V ABI with LP64 data type)
 * data of snd_kcontrol_volatile (16 bytes)

Memory consumption under current limitation:
 (144 + 320 + 1024 * 128) * 32 + (1024 + 16) * 1028 = 5,278,272

Scenario for the worst case when appying the patch:
* adding 32,896 control element sets
 * for elements: (1024 + 16) * 1028 * 32 = 34,211,840
 * for element sets: (144 + 320 + 1024 * 128) * 32896 = 4,327,008,256

Forget my previous patch. The code change suggested there is obviously not sufficient, but you need only consider about its idea.

...

Scenario for the worst case when applying my patch:

• adding 150 control element sets
• for elements: (1024 + 16) * 1028 * 150 = 160,368,000
• for element sets: (144 + 320 + 1024 * 128) * 150 = 19,730,400

See that your patch increases the memory consumption so much? That's my point.

We may give more user elements without increasing the worst-case memory footprint in normal scenarios. So scratch MAX_USER_CONTROLS but count each user element's memory consumption and define its total limit instead.

When preparing for safety, we should not assume anything as long as the worst case is clear, in my opinion.

The initial maximum memory consumption is 5.2 MB. With limitation of control element by control element, it's so large due to the data of TLV per control element set. With limitation of control element set by control element set, it's 19.7 MB and deterministic (in my patch).

It's can be investigated to arrange relevant parameters, but it certainly brings regression to the old-versioned userspace applications. It would not be better to change the size of data of TLV and the number of control elements in control element set.

At first place, my request is to relax limitation according to userspace application. Expansion of memory consumption is unavoidable. The linear increase of memory consumption about which you mentioned is not so worse as a result of compromise to the above.

Regards

Takashi Sakamoto

On Mon, 25 Jan 2021 08:09:10 +0100, Takashi Iwai wrote:

On Mon, 25 Jan 2021 01:56:19 +0100, Takashi Sakamoto wrote:

...

When preparing for safety, we should not assume anything as long as the worst case is clear, in my opinion.

The initial maximum memory consumption is 5.2 MB. With limitation of control element by control element, it's so large due to the data of TLV per control element set. With limitation of control element set by control element set, it's 19.7 MB and deterministic (in my patch).

It's can be investigated to arrange relevant parameters, but it certainly brings regression to the old-versioned userspace applications. It would not be better to change the size of data of TLV and the number of control elements in control element set.

At first place, my request is to relax limitation according to userspace application. Expansion of memory consumption is unavoidable. The linear increase of memory consumption about which you mentioned is not so worse as a result of compromise to the above.

Hm? We really care only the *max* memory consumption case (i.e. the worst case scenario), not about the memory consumption in your particular use case. And this can be certainly accountable.

Whether to calculate the amount of TLV data separately from the main user elements is another thing to be discussed, but in either way, we can know the data size at allocation time, and we can also calculate the theoretical max of the current implementation beforehand.

Now I counted the actual memory consumption in the old code, and this could lead to ca 32MB without TLV and enum strings. TLV and enum strings may attribute 6MB more total, so it can go up to 38MB. It's really high, and we'd rather want to reduce it, instead of increasing it.

Below is a revised patch, that calculates the memory consumption in more details. In this patch, the max memory is reduced to 8MB -- which should be large enough for any sensible use cases. I guess this will fulfill your requirement?

The patch also makes the limit as a module option. I'm not 100% sure whether it's needed, but since the patch reduces the size, it might need some cure for an extreme case.

Takashi

-- 8< -- From: Takashi Iwai tiwai@suse.de Subject: [PATCH] ALSA: control: Add memory consumption limit to user controls

ALSA control interface allows users to add arbitrary control elements (called "user controls" or "user elements"), and its resource usage is limited just by the max number of control sets (currently 32). This limit, however, is quite loose: each allocation of control set may have 1028 elements, and each element may have up to 512 bytes of value data. Moreover, each control set may contain the enum strings and TLV data, which can be up to 64kB and 128kB, respectively. Totally, the whole memory consumption may go over 38MB -- it's quite large, and we'd rather like to reduce the size.

OTOH, there have been other requests even to increase the max number of user elements; e.g. FireWire stack require the more user controls, hence we want to raise the bar, too.

For satisfying both requirements, this patch changes the management of user controls: instead of setting the upper limit of the number of user controls, we check the actual memory allocation size and set the upper limit of the total allocation in bytes. As long as the memory consumption stays below the limit, more user controls are allowed than the current limit 32. At the same time, we set the lower limit (8MB) as default than the current theoretical limit, in order to lower the risk of DoS.

As a compromise for lowering the default limit, now the actual memory limit is defined as a module option, max_user_ctl, so that user can increase/decrease the limit if really needed, too.

Signed-off-by: Takashi Iwai tiwai@suse.de --- include/sound/core.h | 2 +- sound/core/control.c | 66 +++++++++++++++++++++++++++++--------------- 2 files changed, 44 insertions(+), 24 deletions(-)

diff --git a/include/sound/core.h b/include/sound/core.h index 0462c577d7a3..a21b14451810 100644 --- a/include/sound/core.h +++ b/include/sound/core.h @@ -100,7 +100,7 @@ struct snd_card { struct rw_semaphore controls_rwsem; /* controls list lock */ rwlock_t ctl_files_rwlock; /* ctl_files list lock */ int controls_count; /* count of all controls */ - int user_ctl_count; /* count of all user controls */ + size_t user_ctl_alloc_size; /* current memory allocation by user controls */ struct list_head controls; /* all controls for this card */ struct list_head ctl_files; /* active control files */

diff --git a/sound/core/control.c b/sound/core/control.c index 5165741a8400..bbc4ee61f965 100644 --- a/sound/core/control.c +++ b/sound/core/control.c @@ -7,6 +7,7 @@ #include <linux/threads.h> #include <linux/interrupt.h> #include <linux/module.h> +#include <linux/moduleparam.h> #include <linux/slab.h> #include <linux/vmalloc.h> #include <linux/time.h> @@ -18,10 +19,13 @@ #include <sound/info.h> #include <sound/control.h>

-/* max number of user-defined controls */ -#define MAX_USER_CONTROLS 32 #define MAX_CONTROL_COUNT 1028

+/* Max allocation size for user controls */ +static int max_user_ctl_alloc_size = 8 * 1024 * 1024; +module_param_named(max_user_ctl, max_user_ctl_alloc_size, int, 0444); +MODULE_PARM_DESC(max_user_ctl, "Max allocation size for user controls"); + struct snd_kctl_ioctl { struct list_head list; /* list of all ioctls */ snd_kctl_ioctl_func_t fioctl; @@ -537,9 +541,6 @@ static int snd_ctl_remove_user_ctl(struct snd_ctl_file * file, goto error; } ret = snd_ctl_remove(card, kctl); - if (ret < 0) - goto error; - card->user_ctl_count--; error: up_write(&card->controls_rwsem); return ret; @@ -1226,11 +1227,18 @@ struct user_element { struct snd_card *card; char *elem_data; /* element data */ unsigned long elem_data_size; /* size of element data in bytes */ + size_t alloc_size; /* allocated size */ void *tlv_data; /* TLV data */ unsigned long tlv_data_size; /* TLV data size */ void *priv_data; /* private data (like strings for enumerated type) */ };

+/* check whether the addition (in bytes) of user ctl element may overflow the limit */ +static bool user_elem_overflow(struct snd_card *card, ssize_t add) +{ + return (ssize_t)card->user_ctl_alloc_size + add >= max_user_ctl_alloc_size; +} + static int snd_ctl_elem_user_info(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo) { @@ -1309,6 +1317,10 @@ static int replace_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf, if (size > 1024 * 128) /* sane value */ return -EINVAL;

+ /* does the TLV size change cause overflow? */ + if (user_elem_overflow(ue->card, (ssize_t)(size - ue->tlv_data_size))) + return -ENOMEM; + container = vmemdup_user(buf, size); if (IS_ERR(container)) return PTR_ERR(container); @@ -1326,11 +1338,15 @@ static int replace_user_tlv(struct snd_kcontrol *kctl, unsigned int __user *buf, for (i = 0; i < kctl->count; ++i) kctl->vd[i].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ; mask = SNDRV_CTL_EVENT_MASK_INFO; + } else { + ue->card->user_ctl_alloc_size -= ue->tlv_data_size; + ue->tlv_data_size = 0; + kvfree(ue->tlv_data); }

- kvfree(ue->tlv_data); ue->tlv_data = container; ue->tlv_data_size = size; + ue->card->user_ctl_alloc_size += size;

mask |= SNDRV_CTL_EVENT_MASK_TLV; for (i = 0; i < kctl->count; ++i) { @@ -1374,16 +1390,17 @@ static int snd_ctl_elem_init_enum_names(struct user_element *ue) unsigned int i; const uintptr_t user_ptrval = ue->info.value.enumerated.names_ptr;

- if (ue->info.value.enumerated.names_length > 64 * 1024) + buf_len = ue->info.value.enumerated.names_length; + if (buf_len > 64 * 1024) return -EINVAL;

- names = vmemdup_user((const void __user *)user_ptrval, - ue->info.value.enumerated.names_length); + if (user_elem_overflow(ue->card, buf_len)) + return -ENOMEM; + names = vmemdup_user((const void __user *)user_ptrval, buf_len); if (IS_ERR(names)) return PTR_ERR(names);

/* check that there are enough valid names */ - buf_len = ue->info.value.enumerated.names_length; p = names; for (i = 0; i < ue->info.value.enumerated.items; ++i) { name_len = strnlen(p, buf_len); @@ -1397,6 +1414,7 @@ static int snd_ctl_elem_init_enum_names(struct user_element *ue)

ue->priv_data = names; ue->info.value.enumerated.names_ptr = 0; + ue->alloc_size += buf_len;

return 0; } @@ -1405,6 +1423,8 @@ static void snd_ctl_elem_user_free(struct snd_kcontrol *kcontrol) { struct user_element *ue = kcontrol->private_data;

+ ue->card->user_ctl_alloc_size -= ue->alloc_size; + ue->card->user_ctl_alloc_size -= ue->tlv_data_size; kvfree(ue->tlv_data); kvfree(ue->priv_data); kfree(ue); @@ -1418,6 +1438,7 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, unsigned int count; unsigned int access; long private_size; + size_t alloc_size; struct user_element *ue; unsigned int offset; int err; @@ -1435,13 +1456,6 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, return err; }

- /* - * The number of userspace controls are counted control by control, - * not element by element. - */ - if (card->user_ctl_count + 1 > MAX_USER_CONTROLS) - return -ENOMEM; - /* Check the number of elements for this userspace control. */ count = info->owner; if (count == 0) @@ -1472,6 +1486,11 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, if (info->count < 1) return -EINVAL; private_size = value_sizes[info->type] * info->count; + alloc_size = sizeof(struct user_element) + private_size * count; + + /* Check the memory allocation limit */ + if (user_elem_overflow(card, alloc_size)) + return -ENOMEM;

/* * Keep memory object for this userspace control. After passing this @@ -1483,19 +1502,22 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, if (err < 0) return err; memcpy(&kctl->id, &info->id, sizeof(kctl->id)); - kctl->private_data = kzalloc(sizeof(struct user_element) + private_size * count, - GFP_KERNEL); - if (kctl->private_data == NULL) { + ue = kzalloc(alloc_size, GFP_KERNEL); + if (!ue) { kfree(kctl); return -ENOMEM; } + kctl->private_data = ue; kctl->private_free = snd_ctl_elem_user_free;

+ /* increment the allocated size; decremented again at private_free */ + card->user_ctl_alloc_size += alloc_size; + /* Set private data for this userspace control. */ - ue = (struct user_element *)kctl->private_data; ue->card = card; ue->info = *info; ue->info.access = 0; + ue->alloc_size = alloc_size; ue->elem_data = (char *)ue + sizeof(*ue); ue->elem_data_size = private_size; if (ue->info.type == SNDRV_CTL_ELEM_TYPE_ENUMERATED) { @@ -1535,8 +1557,6 @@ static int snd_ctl_elem_add(struct snd_ctl_file *file, * which locks the element. */

- card->user_ctl_count++; - unlock: up_write(&card->controls_rwsem); return err;

On Tue, 26 Jan 2021 17:25:24 +0100, Jaroslav Kysela wrote:

Dne 26. 01. 21 v 16:57 Takashi Iwai napsal(a):

...

@@ -1226,11 +1227,18 @@ struct user_element { struct snd_card *card; char *elem_data; /* element data */ unsigned long elem_data_size; /* size of element data in bytes */

• size_t alloc_size; /* allocated size */

I think that introduction of this new member is not required. The allocated size can be easily computed at runtime (function).

True. OTOH, I thought this addition would be error-prone.

...

@@ -1397,6 +1414,7 @@ static int snd_ctl_elem_init_enum_names(struct user_element *ue)

ue->priv_data = names; ue->info.value.enumerated.names_ptr = 0;

• ue->alloc_size += buf_len;

The buf_len variable is the remaining count. The ue->info.value.enumerated.names_length already contains allocated bytes. This code can be elimited if alloc_size is not introduced.

Oh yeah, that's a wrong count.

thanks,

Takashi