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Wed, 7 Oct 2026 09:36:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 9oTPLKgSxmpMDgAAD6G6ig:T6 (envelope-from ); Wed, 07 Oct 2026 09:36:41 +0000 From: Takashi Iwai To: linux-sound@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH v2 5/8] ALSA: usb-audio: Fix data race at mixer_ctl_feature_info() Date: Wed, 7 Oct 2026 11:36:32 +0200 Message-ID: <20261007093638.1049688-6-tiwai@suse.de> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261007093638.1049688-1-tiwai@suse.de> References: <20261007093638.1049688-1-tiwai@suse.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Flag: NO X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; RCPT_COUNT_TWO(0.00)[2]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,imap1.dmz-prg2.suse.org:helo]; URIBL_BLOCKED(0.00)[suse.de:email,imap1.dmz-prg2.suse.org:helo]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TO_DN_NONE(0.00)[]; RCVD_TLS_ALL(0.00)[] X-Spam-Score: -2.80 X-Spam-Level: The info callback for USB-audio mixer controls for feature unit has a dynamic initialization of the contents with the check of cval->initialized flag. But, since the info callback may be concurrently called, this may lead to a data race, giving back an inconsistent state. Similarly, get and put callbacks may have concurrent accesses and can get bogus states. For avoiding the data race, introduce a mutex locking for the controls and protect against concurrent info callback calls. Reported-by: Sashiko Signed-off-by: Takashi Iwai --- v1->v2: fix mutex() scope in mixer_ctl_feature_info sound/usb/mixer.c | 11 ++++++++++- sound/usb/mixer.h | 1 + 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 9d8007ea95d5..3b6e8759130d 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -1531,6 +1531,7 @@ static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol, struct usb_mixer_elem_info *cval = snd_kcontrol_chip(kcontrol); int ret; + guard(mutex)(&cval->head.mixer->lock); if (cval->val_type == USB_MIXER_BOOLEAN || cval->val_type == USB_MIXER_INV_BOOLEAN) uinfo->type = SNDRV_CTL_ELEM_TYPE_BOOLEAN; @@ -1565,6 +1566,7 @@ static int mixer_ctl_feature_get(struct snd_kcontrol *kcontrol, struct usb_mixer_elem_info *cval = snd_kcontrol_chip(kcontrol); int c, cnt, val, err; + guard(mutex)(&cval->head.mixer->lock); ucontrol->value.integer.value[0] = cval->min; if (cval->cmask) { cnt = 0; @@ -1595,10 +1597,12 @@ static int mixer_ctl_feature_put(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol) { struct usb_mixer_elem_info *cval = snd_kcontrol_chip(kcontrol); - int max_val = get_max_exposed(cval); + int max_val; int c, cnt, val, oval, err; int changed = 0; + guard(mutex)(&cval->head.mixer->lock); + max_val = get_max_exposed(cval); if (cval->cmask) { cnt = 0; for (c = 0; c < MAX_CHANNELS; c++) { @@ -1646,6 +1650,7 @@ static int mixer_ctl_master_bool_get(struct snd_kcontrol *kcontrol, struct usb_mixer_elem_info *cval = snd_kcontrol_chip(kcontrol); int val, err; + guard(mutex)(&cval->head.mixer->lock); err = snd_usb_get_cur_mix_value(cval, 0, 0, &val); if (err < 0) return filter_error(cval, err); @@ -2592,6 +2597,7 @@ static int mixer_ctl_procunit_get(struct snd_kcontrol *kcontrol, struct usb_mixer_elem_info *cval = snd_kcontrol_chip(kcontrol); int err, val; + guard(mutex)(&cval->head.mixer->lock); err = get_cur_ctl_value(cval, cval->control << 8, &val); if (err < 0) { ucontrol->value.integer.value[0] = cval->min; @@ -2609,6 +2615,7 @@ static int mixer_ctl_procunit_put(struct snd_kcontrol *kcontrol, struct usb_mixer_elem_info *cval = snd_kcontrol_chip(kcontrol); int val, oval, err; + guard(mutex)(&cval->head.mixer->lock); err = get_cur_ctl_value(cval, cval->control << 8, &oval); if (err < 0) return filter_error(cval, err); @@ -3249,6 +3256,7 @@ static void snd_usb_mixer_free(struct usb_mixer_interface *mixer) } usb_free_urb(mixer->rc_urb); kfree(mixer->rc_setup_packet); + mutex_destroy(&mixer->lock); kfree(mixer); } @@ -3885,6 +3893,7 @@ int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif) mixer = kzalloc_obj(*mixer); if (!mixer) return -ENOMEM; + mutex_init(&mixer->lock); mixer->chip = chip; mixer->ignore_ctl_error = !!(chip->quirk_flags & QUIRK_FLAG_IGNORE_CTL_ERROR); mixer->id_elems = kzalloc_objs(*mixer->id_elems, MAX_ID_ELEMS); diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h index cf45c39cbccc..2ff4490f97c2 100644 --- a/sound/usb/mixer.h +++ b/sound/usb/mixer.h @@ -18,6 +18,7 @@ struct usb_mixer_interface { struct usb_host_interface *hostif; struct list_head list; unsigned int ignore_ctl_error; + struct mutex lock; /* lock for feature unit callbacks */ /* UAC2 status interrupt endpoint; owned by mixer.c */ struct urb *urb; /* array[MAX_ID_ELEMS], indexed by unit id */ -- 2.55.0