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Fri, 21 Aug 2026 02:23:01 -0700 (PDT) From: Javier Carrasco Date: Fri, 21 Aug 2026 11:22:58 +0200 Subject: [PATCH] hwmon: chipcap2: serialize access to low/high_alarm indicators Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260821-chipcap2_locks-v1-1-1d8ccabfc1b2@gmail.com> X-B4-Tracking: v=1; b=H4sIAPEYiGoC/x3MQQqAMAwAwa9IzhbSKCJ+RURKjBqUtrQggvh3i 8c57D6QJalkGKoHklyaNfgCW1fAu/ObGF2KgZA67AkN7xrZRZrPwEc2jBZt46h1yFCimGTV+x+ O0/t+AsOkw2AAAAA= To: Guenter Roeck Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Javier Carrasco X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1787304180; l=3705; i=javier.carrasco.cruz@gmail.com; s=20260111; h=from:subject:message-id; bh=hQO8OzIVbst3gIhi1BPiKl2+n+sX9ZozFDZUJ3vY23Q=; b=gn6eIx5NH+nYnnoXMg3uiFNVQ7ZcHyk3qw7tztgrwlY7P2AfXUb254l2Bzvi9xA0g9HLZp2r1 VexGu29P6rNAn9ZCNX0580w6Qt7JXhaCUdw7V0VrLnAEq4lq8H40V9t X-Developer-Key: i=javier.carrasco.cruz@gmail.com; a=ed25519; pk=Lge8w8xidNSf/INy7JAIbAW+Hezkp3nsBh2OjKL7lLU= Access to low_alarm and high_alarm from the threaded interrupt handlers and sysfs is not protected by any locking mechanism at the moment, which can lead to missed events. Add a per-interrupt mutex as the two alarm indicators are completely independent. Fixes: 3af350929e75 ("hwmon: Add support for Amphenol ChipCap 2") Cc: stable@vger.kernel.org Signed-off-by: Javier Carrasco --- This issue was found by Sashiko[1] when an unrelated patch affected chipcap2.c. The issue is real as the access to the variables is not protected by any locking mechanism although 2 different sources (threaded interrupts and sysfs) could modify them. The fix has been validated on real hardware with an Amphenol ChipCap 2 CC2D23S sensor. Link: [1] https://lore.kernel.org/linux-hwmon/20260625162114.417EA1F000E9@smtp.kernel.org/ --- drivers/hwmon/chipcap2.c | 38 ++++++++++++++++++++++++++++---------- 1 file changed, 28 insertions(+), 10 deletions(-) diff --git a/drivers/hwmon/chipcap2.c b/drivers/hwmon/chipcap2.c index 086571d556b7..1bb4ec96514e 100644 --- a/drivers/hwmon/chipcap2.c +++ b/drivers/hwmon/chipcap2.c @@ -73,7 +73,11 @@ struct cc2_rh_alarm_info { bool low_alarm; + /* Serialize accesses to low_alarm from threaded IRQ and sysfs */ + struct mutex low_alarm_lock; bool high_alarm; + /* Serialize accesses to high_alarm from threaded IRQ and sysfs */ + struct mutex high_alarm_lock; bool low_alarm_visible; bool high_alarm_visible; }; @@ -500,6 +504,7 @@ static irqreturn_t cc2_low_interrupt(int irq, void *data) if (cc2->process_irqs) { hwmon_notify_event(cc2->hwmon, hwmon_humidity, hwmon_humidity_min_alarm, CC2_CHAN_HUMIDITY); + guard(mutex)(&cc2->rh_alarm.low_alarm_lock); cc2->rh_alarm.low_alarm = true; } @@ -513,6 +518,7 @@ static irqreturn_t cc2_high_interrupt(int irq, void *data) if (cc2->process_irqs) { hwmon_notify_event(cc2->hwmon, hwmon_humidity, hwmon_humidity_max_alarm, CC2_CHAN_HUMIDITY); + guard(mutex)(&cc2->rh_alarm.high_alarm_lock); cc2->rh_alarm.high_alarm = true; } @@ -529,11 +535,13 @@ static int cc2_humidity_min_alarm_status(struct cc2_data *data, long *val) if (ret < 0) return ret; - if (data->rh_alarm.low_alarm) { - *val = (measurement < min_hyst) ? 1 : 0; - data->rh_alarm.low_alarm = *val; - } else { - *val = 0; + scoped_guard(mutex, &data->rh_alarm.low_alarm_lock) { + if (data->rh_alarm.low_alarm) { + *val = (measurement < min_hyst) ? 1 : 0; + data->rh_alarm.low_alarm = *val; + } else { + *val = 0; + } } return 0; @@ -549,11 +557,13 @@ static int cc2_humidity_max_alarm_status(struct cc2_data *data, long *val) if (ret < 0) return ret; - if (data->rh_alarm.high_alarm) { - *val = (measurement > max_hyst) ? 1 : 0; - data->rh_alarm.high_alarm = *val; - } else { - *val = 0; + scoped_guard(mutex, &data->rh_alarm.high_alarm_lock) { + if (data->rh_alarm.high_alarm) { + *val = (measurement > max_hyst) ? 1 : 0; + data->rh_alarm.high_alarm = *val; + } else { + *val = 0; + } } return 0; @@ -720,6 +730,14 @@ static int cc2_probe(struct i2c_client *client) if (!data) return -ENOMEM; + ret = devm_mutex_init(dev, &data->rh_alarm.low_alarm_lock); + if (ret) + return ret; + + ret = devm_mutex_init(dev, &data->rh_alarm.high_alarm_lock); + if (ret) + return ret; + i2c_set_clientdata(client, data); data->client = client; --- base-commit: 818bebeb63dd6bf5f4e07e145f6cdbace520a34c change-id: 20260820-chipcap2_locks-c01013a24a0c Best regards, -- Javier Carrasco