mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

As &chip->pm_irq_lock is acquired by pm8xxx_irq_handler() under irq
context, other process context code should disable irq before acquiring
the lock.

Since .irq_set_type and .irq_get_irqchip_state callbacks are generally
executed from process context without irq disabled by default, the same
lock acquision should disable irq.

Possible deadlock scenario
pm8xxx_irq_set_type()
    -> pm8xxx_config_irq()
    -> spin_lock(&chip->pm_irq_lock)
        <irq interrupt>
        -> pm8xxx_irq_handler()
        -> pm8xxx_irq_master_handler()
        -> pm8xxx_irq_block_handler()
        -> pm8xxx_read_block_irq()
        -> spin_lock(&chip->pm_irq_lock) (deadlock here)

This flaw was found using an experimental static analysis tool we are
developing for irq-related deadlock.

Fix the potential deadlock by spin_lock_irqsave().

Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Reviewed-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Link: https://lore.kernel.org/r/20230720071330.50382-1-dg573847474@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>

diff --git a/drivers/mfd/qcom-pm8xxx.c b/drivers/mfd/qcom-pm8xxx.c
index 9a948df..07c531b 100644 (file)
--- a/drivers/mfd/qcom-pm8xxx.c
+++ b/drivers/mfd/qcom-pm8xxx.c
@@ -103,8 +103,9 @@ static int
 pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
 {
        int     rc;
+       unsigned long flags;
 
-       spin_lock(&chip->pm_irq_lock);
+       spin_lock_irqsave(&chip->pm_irq_lock, flags);
        rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, bp);
        if (rc) {
                pr_err("Failed Selecting Block %d rc=%d\n", bp, rc);
@@ -116,7 +117,7 @@ pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
        if (rc)
                pr_err("Failed Configuring IRQ rc=%d\n", rc);
 bail:
-       spin_unlock(&chip->pm_irq_lock);
+       spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
        return rc;
 }
 
@@ -321,6 +322,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
        struct pm_irq_chip *chip = irq_data_get_irq_chip_data(d);
        unsigned int pmirq = irqd_to_hwirq(d);
        unsigned int bits;
+       unsigned long flags;
        int irq_bit;
        u8 block;
        int rc;
@@ -331,7 +333,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
        block = pmirq / 8;
        irq_bit = pmirq % 8;
 
-       spin_lock(&chip->pm_irq_lock);
+       spin_lock_irqsave(&chip->pm_irq_lock, flags);
        rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, block);
        if (rc) {
                pr_err("Failed Selecting Block %d rc=%d\n", block, rc);
@@ -346,7 +348,7 @@ static int pm8xxx_irq_get_irqchip_state(struct irq_data *d,
 
        *state = !!(bits & BIT(irq_bit));
 bail:
-       spin_unlock(&chip->pm_irq_lock);
+       spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
 
        return rc;
 }