[PATCH 5.15.y 2/2] gpio: sch: use raw_spinlock_t in the irq startup path

[Sasha Levin <sashal@kernel.org>]

From: Runyu Xiao <runyu.xiao@seu.edu.cn>

[ Upstream commit 286533cb14a3c8a8bd39ff64ea2fc8e1aa0f638b ]

sch_irq_unmask() enables the GPIO IRQ and then updates the controller
state through sch_irq_mask_unmask(), which takes sch->lock with
spin_lock_irqsave().  The callback can be reached from irq_startup()
while setting up a requested IRQ.  That path is not sleepable, but on
PREEMPT_RT a regular spinlock_t becomes a sleeping lock.

This issue was found by our static analysis tool and then manually
reviewed against the current tree.

The grounded PoC kept the request_threaded_irq() -> __setup_irq() ->
irq_startup() -> sch_irq_unmask() -> sch_irq_mask_unmask() carrier and
used the original spin_lock_irqsave(&sch->lock) edge.  Lockdep reported:

  BUG: sleeping function called from invalid context
  hardirqs last disabled at ... __setup_irq.constprop.0 ... [vuln_msv]
  sch_rt_spin_lock_irqsave+0x1c/0x30 [vuln_msv]
  sch_irq_mask_unmask.constprop.0+0x31/0x70 [vuln_msv]
  __setup_irq.constprop.0+0xd/0x30 [vuln_msv]

Convert the SCH controller lock to raw_spinlock_t.  The same lock is
also used by the GPIO direction and value callbacks, but those critical
sections only update MMIO-backed GPIO registers and do not contain
sleepable operations.  Keeping this register lock non-sleeping is
therefore appropriate for the irqchip callbacks and does not change the
GPIO-side locking contract.

Fixes: 7a81638485c1 ("gpio: sch: Add edge event support")
Cc: stable@vger.kernel.org
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Link: https://patch.msgid.link/20260617154035.1199948-2-runyu.xiao@seu.edu.cn
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpio/gpio-sch.c | 41 ++++++++++++++++++++---------------------
 1 file changed, 20 insertions(+), 21 deletions(-)

diff --git a/drivers/gpio/gpio-sch.c b/drivers/gpio/gpio-sch.c
index 2b19e978c034d8..fd0f0e677b2ecc 100644
--- a/drivers/gpio/gpio-sch.c
+++ b/drivers/gpio/gpio-sch.c
@@ -39,7 +39,7 @@
 struct sch_gpio {
 	struct gpio_chip chip;
 	struct irq_chip irqchip;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	unsigned short iobase;
 	unsigned short resume_base;
 
@@ -103,9 +103,9 @@ static int sch_gpio_direction_in(struct gpio_chip *gc, unsigned int gpio_num)
 	struct sch_gpio *sch = gpiochip_get_data(gc);
 	unsigned long flags;
 
-	spin_lock_irqsave(&sch->lock, flags);
+	raw_spin_lock_irqsave(&sch->lock, flags);
 	sch_gpio_reg_set(sch, gpio_num, GIO, 1);
-	spin_unlock_irqrestore(&sch->lock, flags);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 	return 0;
 }
 
@@ -116,16 +116,14 @@ static int sch_gpio_get(struct gpio_chip *gc, unsigned int gpio_num)
 	return sch_gpio_reg_get(sch, gpio_num, GLV);
 }
 
-static int sch_gpio_set(struct gpio_chip *gc, unsigned int gpio_num, int val)
+static void sch_gpio_set(struct gpio_chip *gc, unsigned int gpio_num, int val)
 {
 	struct sch_gpio *sch = gpiochip_get_data(gc);
 	unsigned long flags;
 
-	spin_lock_irqsave(&sch->lock, flags);
+	raw_spin_lock_irqsave(&sch->lock, flags);
 	sch_gpio_reg_set(sch, gpio_num, GLV, val);
-	spin_unlock_irqrestore(&sch->lock, flags);
-
-	return 0;
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 }
 
 static int sch_gpio_direction_out(struct gpio_chip *gc, unsigned int gpio_num,
@@ -134,9 +132,9 @@ static int sch_gpio_direction_out(struct gpio_chip *gc, unsigned int gpio_num,
 	struct sch_gpio *sch = gpiochip_get_data(gc);
 	unsigned long flags;
 
-	spin_lock_irqsave(&sch->lock, flags);
+	raw_spin_lock_irqsave(&sch->lock, flags);
 	sch_gpio_reg_set(sch, gpio_num, GIO, 0);
-	spin_unlock_irqrestore(&sch->lock, flags);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 
 	/*
 	 * according to the datasheet, writing to the level register has no
@@ -147,7 +145,8 @@ static int sch_gpio_direction_out(struct gpio_chip *gc, unsigned int gpio_num,
 	 * But we cannot prevent a short low pulse if direction is set to high
 	 * and an external pull-up is connected.
 	 */
-	return sch_gpio_set(gc, gpio_num, val);
+	sch_gpio_set(gc, gpio_num, val);
+	return 0;
 }
 
 static int sch_gpio_get_direction(struct gpio_chip *gc, unsigned int gpio_num)
@@ -166,7 +165,7 @@ static const struct gpio_chip sch_gpio_chip = {
 	.direction_input	= sch_gpio_direction_in,
 	.get			= sch_gpio_get,
 	.direction_output	= sch_gpio_direction_out,
-	.set_rv			= sch_gpio_set,
+	.set			= sch_gpio_set,
 	.get_direction		= sch_gpio_get_direction,
 };
 
@@ -195,14 +194,14 @@ static int sch_irq_type(struct irq_data *d, unsigned int type)
 		return -EINVAL;
 	}
 
-	spin_lock_irqsave(&sch->lock, flags);
+	raw_spin_lock_irqsave(&sch->lock, flags);
 
 	sch_gpio_reg_set(sch, gpio_num, GTPE, rising);
 	sch_gpio_reg_set(sch, gpio_num, GTNE, falling);
 
 	irq_set_handler_locked(d, handle_edge_irq);
 
-	spin_unlock_irqrestore(&sch->lock, flags);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 
 	return 0;
 }
@@ -214,9 +213,9 @@ static void sch_irq_ack(struct irq_data *d)
 	irq_hw_number_t gpio_num = irqd_to_hwirq(d);
 	unsigned long flags;
 
-	spin_lock_irqsave(&sch->lock, flags);
+	raw_spin_lock_irqsave(&sch->lock, flags);
 	sch_gpio_reg_set(sch, gpio_num, GTS, 1);
-	spin_unlock_irqrestore(&sch->lock, flags);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 }
 
 static void sch_irq_mask_unmask(struct irq_data *d, int val)
@@ -226,9 +225,9 @@ static void sch_irq_mask_unmask(struct irq_data *d, int val)
 	irq_hw_number_t gpio_num = irqd_to_hwirq(d);
 	unsigned long flags;
 
-	spin_lock_irqsave(&sch->lock, flags);
+	raw_spin_lock_irqsave(&sch->lock, flags);
 	sch_gpio_reg_set(sch, gpio_num, GGPE, val);
-	spin_unlock_irqrestore(&sch->lock, flags);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 }
 
 static void sch_irq_mask(struct irq_data *d)
@@ -251,12 +250,12 @@ static u32 sch_gpio_gpe_handler(acpi_handle gpe_device, u32 gpe, void *context)
 	int offset;
 	u32 ret;
 
-	spin_lock_irqsave(&sch->lock, flags);
+	raw_spin_lock_irqsave(&sch->lock, flags);
 
 	core_status = inl(sch->iobase + CORE_BANK_OFFSET + GTS);
 	resume_status = inl(sch->iobase + RESUME_BANK_OFFSET + GTS);
 
-	spin_unlock_irqrestore(&sch->lock, flags);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 
 	pending = (resume_status << sch->resume_base) | core_status;
 	for_each_set_bit(offset, &pending, sch->chip.ngpio)
@@ -322,7 +321,7 @@ static int sch_gpio_probe(struct platform_device *pdev)
 				 pdev->name))
 		return -EBUSY;
 
-	spin_lock_init(&sch->lock);
+	raw_spin_lock_init(&sch->lock);
 	sch->iobase = res->start;
 	sch->chip = sch_gpio_chip;
 	sch->chip.label = dev_name(&pdev->dev);
-- 
2.53.0