[PATCH 6.6.y] 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>
[ adjusted context for 6.6's pre-MMIO `iobase` port I/O and void `sch_gpio_set()` (no set_rv `return 0;`) ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpio/gpio-sch.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/gpio/gpio-sch.c b/drivers/gpio/gpio-sch.c
index e48392074e4b86..a53946859c8c1f 100644
--- a/drivers/gpio/gpio-sch.c
+++ b/drivers/gpio/gpio-sch.c
@@ -38,7 +38,7 @@
 
 struct sch_gpio {
 	struct gpio_chip chip;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	unsigned short iobase;
 	unsigned short resume_base;
 
@@ -102,9 +102,9 @@ 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;
 }
 
@@ -120,9 +120,9 @@ 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);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 }
 
 static int sch_gpio_direction_out(struct gpio_chip *gc, unsigned int gpio_num,
@@ -131,9 +131,9 @@ 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
@@ -193,14 +193,14 @@ 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;
 }
@@ -212,9 +212,9 @@ 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 gpio_chip *gc, irq_hw_number_t gpio_num, int val)
@@ -222,9 +222,9 @@ static void sch_irq_mask_unmask(struct gpio_chip *gc, irq_hw_number_t 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, GGPE, val);
-	spin_unlock_irqrestore(&sch->lock, flags);
+	raw_spin_unlock_irqrestore(&sch->lock, flags);
 }
 
 static void sch_irq_mask(struct irq_data *d)
@@ -265,12 +265,12 @@ 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)
@@ -336,7 +336,7 @@ 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