gpio: gpio-grgpio: fix possible sleep-in-atomic-context bugs in grgpio_irq_map/unmap()

The driver may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:

drivers/gpio/gpio-grgpio.c, 261:
	request_irq in grgpio_irq_map
drivers/gpio/gpio-grgpio.c, 255:
	_raw_spin_lock_irqsave in grgpio_irq_map

drivers/gpio/gpio-grgpio.c, 318:
	free_irq in grgpio_irq_unmap
drivers/gpio/gpio-grgpio.c, 299:
	_raw_spin_lock_irqsave in grgpio_irq_unmap

request_irq() and free_irq() can sleep at runtime.

To fix these bugs, request_irq() and free_irq() are called without
holding the spinlock.

These bugs are found by a static analysis tool STCheck written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Link: https://lore.kernel.org/r/20191218132605.10594-1-baijiaju1990@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpio-grgpio.c b/drivers/gpio/gpio-grgpio.c
index a49f0711ca944db5fa54291b23cea277805c80c2..1922adf96fc94d81576d29b7c2c08c4b989d3e43 100644 (file)
--- a/drivers/gpio/gpio-grgpio.c
+++ b/drivers/gpio/gpio-grgpio.c
@@ -253,17 +253,16 @@ static int grgpio_irq_map(struct irq_domain *d, unsigned int irq,
        lirq->irq = irq;
        uirq = &priv->uirqs[lirq->index];
        if (uirq->refcnt == 0) {
+               spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
                ret = request_irq(uirq->uirq, grgpio_irq_handler, 0,
                                  dev_name(priv->dev), priv);
                if (ret) {
                        dev_err(priv->dev,
                                "Could not request underlying irq %d\n",
                                uirq->uirq);
-
-                       spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
-
                        return ret;
                }
+               spin_lock_irqsave(&priv->gc.bgpio_lock, flags);
        }
        uirq->refcnt++;
 
@@ -309,8 +308,11 @@ static void grgpio_irq_unmap(struct irq_domain *d, unsigned int irq)
        if (index >= 0) {
                uirq = &priv->uirqs[lirq->index];
                uirq->refcnt--;
-               if (uirq->refcnt == 0)
+               if (uirq->refcnt == 0) {
+                       spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);
                        free_irq(uirq->uirq, priv);
+                       return;
+               }
        }
 
        spin_unlock_irqrestore(&priv->gc.bgpio_lock, flags);