linux.git/sound/core/control.c, branch v6.1.2

ALSA: control: add snd_ctl_rename()

2022-10-21T06:17:08+00:00

Add a snd_ctl_rename() function that takes care of updating the control
hash entries for callers that already have the relevant struct snd_kcontrol
at hand and hold the control write lock (or simply haven't registered the
card yet).

Fixes: c27e1efb61c5 ("ALSA: control: Use xarray for faster lookups")
Cc: stable@vger.kernel.org
Signed-off-by: Maciej S. Szmigiero 
Link: https://lore.kernel.org/r/4170b71117ea81357a4f7eb8410f7cde20836c70.1666296963.git.maciej.szmigiero@oracle.com
Signed-off-by: Takashi Iwai

ALSA: control: Re-order bounds checking in get_ctl_id_hash()

2022-08-26T15:17:22+00:00

These two checks are in the reverse order so it might read one element
beyond the end of the array.  First check if the "i" is within bounds
before using it.

Fixes: 6ab55ec0a938 ("ALSA: control: Fix an out-of-bounds bug in get_ctl_id_hash()")
Signed-off-by: Dan Carpenter 
Link: https://lore.kernel.org/r/YwjgNh/gkG1hH7po@kili
Signed-off-by: Takashi Iwai

ALSA: control: Fix an out-of-bounds bug in get_ctl_id_hash()

2022-08-24T09:41:53+00:00

Since the user can control the arguments provided to the kernel by the
ioctl() system call, an out-of-bounds bug occurs when the 'id->name'
provided by the user does not end with '\0'.

The following log can reveal it:

[    10.002313] BUG: KASAN: stack-out-of-bounds in snd_ctl_find_id+0x36c/0x3a0
[    10.002895] Read of size 1 at addr ffff888109f5fe28 by task snd/439
[    10.004934] Call Trace:
[    10.007140]  snd_ctl_find_id+0x36c/0x3a0
[    10.007489]  snd_ctl_ioctl+0x6cf/0x10e0

Fix this by checking the bound of 'id->name' in the loop.

Fixes: c27e1efb61c5 ("ALSA: control: Use xarray for faster lookups")
Signed-off-by: Zheyu Ma 
Link: https://lore.kernel.org/r/20220824081654.3767739-1-zheyuma97@gmail.com
Signed-off-by: Takashi Iwai

ALSA: control: Use deferred fasync helper

2022-07-29T10:57:12+00:00

For avoiding the potential deadlock via kill_fasync() call, use the
new fasync helpers to defer the invocation from the control API.  Note
that it's merely a workaround.

Another note: although we haven't received reports about the deadlock
with the control API, the deadlock is still potentially possible, and
it's better to align the behavior with other core APIs (PCM and
timer); so let's move altogether.

Link: https://lore.kernel.org/r/20220728125945.29533-5-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: control: Fix missing return value comments for kernel docs

2022-07-13T11:42:37+00:00

Each kernel doc comment expects the definition of the return value in
proper format.  This patch adds or fixes the missing entries for
control API.

Link: https://lore.kernel.org/r/20220713104759.4365-6-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: control: Add input validation

2022-06-15T05:45:28+00:00

This patch adds a new feature to enable the validation of input data
to control elements in the ALSA core side.  When
CONFIG_SND_CTL_INPUT_VALIDATION is set, ALSA core verifies whether the
each input value via control API is in the defined ranges, also checks
whether it's aligned to the defined steps.  If an invalid value is
detected, ALSA core returns -EINVAL error immediately without passing
further to the driver's callback.  So this is a kind of hardening for
(badly written) drivers that have no proper error checks, at the cost
of a slight performance overhead.

Technically seen, this reuses a part of the existing validation code
for CONFIG_SND_CTL_DEBUG case with a slight modification to suppress
error prints for the input validation.

Link: https://lore.kernel.org/r/20220609120219.3937-5-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: control: Drop superfluous ifdef CONFIG_SND_CTL_DEBUG

2022-06-15T05:45:28+00:00

Compilers should be smart enough to optimize out the dead functions,
so we don't need to define ugly dummy functions with ifdef.

Link: https://lore.kernel.org/r/20220609120219.3937-4-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: control: Rename CONFIG_SND_CTL_VALIDATION to CONFIG_SND_CTL_DEBUG

2022-06-15T05:45:27+00:00

The purpose of CONFIG_SND_CTL_VALIDATION is rather to enable the
debugging feature for the control API.  The validation is only a part
of it.  Let's rename it to be more explicit and intuitive.

While we're at it, let's advertise, give more comment to recommend
this feature for development in the kconfig help text.

Link: https://lore.kernel.org/r/20220609120219.3937-3-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: control: Use xarray for faster lookups

2022-06-15T05:44:55+00:00

The control elements are managed in a single linked list and we
traverse the whole list for matching each numid or ctl id per every
inquiry of a control element.  This is OK-ish for a small number of
elements but obviously it doesn't scale.  Especially the matching with
the ctl id takes time because it checks each field of the snd_ctl_id
element, e.g. the name string is matched with strcmp().

This patch adds the hash tables with Xarray for improving the lookup
speed of a control element.  There are two xarray tables added to the
card; one for numid and another for ctl id.  For the numid, we use the
numid as the index, while for the ctl id, we calculate a hash key.

The lookup is done via a single xa_load() execution.  As long as the
given control element is found on the Xarray table, that's fine, we
can give back a quick lookup result.  The problem is when no entry
hits on the table, and for this case, we have a slight optimization.
Namely, the driver checks whether we had a collision on Xarray table,
and do a fallback search (linear lookup of the full entries) only if a
hash key collision happened beforehand.
So, in theory, the inquiry for a non-existing element might take still
time even with this patch in a worst case, but this must be pretty
rare.

The feature is enabled via CONFIG_SND_CTL_FAST_LOOKUP, which is turned
on as default.  For simplicity, the option can be turned off only when
CONFIG_EXPERT is set ("You are expert? Then you manage 1000 knobs").

Link: https://lore.kernel.org/r/20211028130027.18764-1-tiwai@suse.de
Link: https://lore.kernel.org/r/20220609180504.775-1-tiwai@suse.de
Link: https://lore.kernel.org/all/cover.1653813866.git.quic_rbankapu@quicinc.com/
Link: https://lore.kernel.org/r/20220610064537.18660-1-tiwai@suse.de
Signed-off-by: Takashi Iwai

ALSA: control: Minor optimization for SNDRV_CTL_IOCTL_POWER_STATE

2021-05-25T06:49:06+00:00

Long long time ago, before the proper PM framework was introduced, it
was still possible to reach SNDRV_CTL_IOCTL_POWER ioctl during the
power off state.  This ioctl existed as a main control for the suspend
resume state in the past, but the feature was already dropped along
with the standard PM framework.  Now the read part,
SNDRV_IOCTL_POWER_STATE ioctl, returns practically always D0, and we
can do some minor optimization there.

Reviewed-by: Jaroslav Kysela 
Link: https://lore.kernel.org/r/20210523090920.15345-5-tiwai@suse.de
Signed-off-by: Takashi Iwai