uio: fix a sleep-in-atomic-context bug in uio_dmem_genirq_irqcontrol()

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

kernel/irq/manage.c, 523:
	synchronize_irq in disable_irq
drivers/uio/uio_dmem_genirq.c, 140:
	disable_irq in uio_dmem_genirq_irqcontrol
drivers/uio/uio_dmem_genirq.c, 134:
	_raw_spin_lock_irqsave in uio_dmem_genirq_irqcontrol

synchronize_irq() can sleep at runtime.

To fix this bug, disable_irq() is called without holding the spinlock.

This bug is 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/20191218094405.6009-1-baijiaju1990@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/uio/uio_dmem_genirq.c b/drivers/uio/uio_dmem_genirq.c
index 81c88f7bbbcbb63e0765035f759913aef099745f..f6ab3f28c8382160a2dba51c49079925f5ce69f7 100644 (file)
--- a/drivers/uio/uio_dmem_genirq.c
+++ b/drivers/uio/uio_dmem_genirq.c
@@ -132,11 +132,13 @@ static int uio_dmem_genirq_irqcontrol(struct uio_info *dev_info, s32 irq_on)
        if (irq_on) {
                if (test_and_clear_bit(0, &priv->flags))
                        enable_irq(dev_info->irq);
+               spin_unlock_irqrestore(&priv->lock, flags);
        } else {
-               if (!test_and_set_bit(0, &priv->flags))
+               if (!test_and_set_bit(0, &priv->flags)) {
+                       spin_unlock_irqrestore(&priv->lock, flags);
                        disable_irq(dev_info->irq);
+               }
        }
-       spin_unlock_irqrestore(&priv->lock, flags);
 
        return 0;
 }