spi: fix refcount-related spidev oops-on-rmmod

This addresses other oopsing paths in "spidev" by changing how it manages
refcounting.  It decouples the lifecycle of the per-device data from the
class device (not just the spi device):

  - Use class_{create,destroy} not class_{register,unregister}.
  - Use device_{create,destroy} not device_{register,unregister}.
  - Free the per-device data only when TWO conditions are true:
      * Driver is unbound from underlying SPI device, and
      * Device is no longer open (new)

Also, spi_{get,set}_drvdata not dev_{get,set}_drvdata for simpler code.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Sebastian Siewior <bigeasy@tglx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 34 insertions, 30 deletions

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index 41620c0fb046..799337f7fde1 100644
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -25,6 +25,7 @@
 #include <linux/ioctl.h>
 #include <linux/fs.h>
 #include <linux/device.h>
+#include <linux/err.h>
 #include <linux/list.h>
 #include <linux/errno.h>
 #include <linux/mutex.h>
@@ -67,11 +68,12 @@ static unsigned long	minors[N_SPI_MINORS / BITS_PER_LONG];
                                 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP)
 
 struct spidev_data {
-        struct device           dev;
+        dev_t                   devt;
         spinlock_t              spi_lock;
         struct spi_device       *spi;
         struct list_head        device_entry;
 
+        /* buffer is NULL unless this device is open (users > 0) */
         struct mutex            buf_lock;
         unsigned                users;
         u8                      *buffer;
@@ -467,7 +469,7 @@ static int spidev_open(struct inode *inode, struct file *filp)
         mutex_lock(&device_list_lock);
 
         list_for_each_entry(spidev, &device_list, device_entry) {
-                if (spidev->dev.devt == inode->i_rdev) {
+                if (spidev->devt == inode->i_rdev) {
                         status = 0;
                         break;
                 }
@@ -500,10 +502,22 @@ static int spidev_release(struct inode *inode, struct file *filp)
         mutex_lock(&device_list_lock);
         spidev = filp->private_data;
         filp->private_data = NULL;
+
+        /* last close? */
         spidev->users--;
         if (!spidev->users) {
+                int             dofree;
+
                 kfree(spidev->buffer);
                 spidev->buffer = NULL;
+
+                /* ... after we unbound from the underlying device? */
+                spin_lock_irq(&spidev->spi_lock);
+                dofree = (spidev->spi == NULL);
+                spin_unlock_irq(&spidev->spi_lock);
+
+                if (dofree)
+                        kfree(spidev);
         }
         mutex_unlock(&device_list_lock);
 
@@ -530,19 +544,7 @@ static struct file_operations spidev_fops = {
  * It also simplifies memory management.
  */
 
-static void spidev_classdev_release(struct device *dev)
-{
-        struct spidev_data      *spidev;
-
-        spidev = container_of(dev, struct spidev_data, dev);
-        kfree(spidev);
-}
-
-static struct class spidev_class = {
-        .name           = "spidev",
-        .owner          = THIS_MODULE,
-        .dev_release    = spidev_classdev_release,
-};
+static struct class *spidev_class;
 
 /*-------------------------------------------------------------------------*/
 
@@ -570,20 +572,20 @@ static int spidev_probe(struct spi_device *spi)
         mutex_lock(&device_list_lock);
         minor = find_first_zero_bit(minors, N_SPI_MINORS);
         if (minor < N_SPI_MINORS) {
-                spidev->dev.parent = &spi->dev;
-                spidev->dev.class = &spidev_class;
-                spidev->dev.devt = MKDEV(SPIDEV_MAJOR, minor);
-                snprintf(spidev->dev.bus_id, sizeof spidev->dev.bus_id,
+                struct device *dev;
+
+                spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
+                dev = device_create(spidev_class, &spi->dev, spidev->devt,
                                 "spidev%d.%d",
                                 spi->master->bus_num, spi->chip_select);
-                status = device_register(&spidev->dev);
+                status = IS_ERR(dev) ? PTR_ERR(dev) : 0;
         } else {
                 dev_dbg(&spi->dev, "no minor number available!\n");
                 status = -ENODEV;
         }
         if (status == 0) {
                 set_bit(minor, minors);
-                dev_set_drvdata(&spi->dev, spidev);
+                spi_set_drvdata(spi, spidev);
                 list_add(&spidev->device_entry, &device_list);
         }
         mutex_unlock(&device_list_lock);
@@ -596,19 +598,21 @@ static int spidev_probe(struct spi_device *spi)
 
 static int spidev_remove(struct spi_device *spi)
 {
-        struct spidev_data      *spidev = dev_get_drvdata(&spi->dev);
+        struct spidev_data      *spidev = spi_get_drvdata(spi);
 
         /* make sure ops on existing fds can abort cleanly */
         spin_lock_irq(&spidev->spi_lock);
         spidev->spi = NULL;
+        spi_set_drvdata(spi, NULL);
         spin_unlock_irq(&spidev->spi_lock);
 
         /* prevent new opens */
         mutex_lock(&device_list_lock);
         list_del(&spidev->device_entry);
-        dev_set_drvdata(&spi->dev, NULL);
-        clear_bit(MINOR(spidev->dev.devt), minors);
-        device_unregister(&spidev->dev);
+        device_destroy(spidev_class, spidev->devt);
+        clear_bit(MINOR(spidev->devt), minors);
+        if (spidev->users == 0)
+                kfree(spidev);
         mutex_unlock(&device_list_lock);
 
         return 0;
@@ -644,15 +648,15 @@ static int __init spidev_init(void)
         if (status < 0)
                 return status;
 
-        status = class_register(&spidev_class);
-        if (status < 0) {
+        spidev_class = class_create(THIS_MODULE, "spidev");
+        if (IS_ERR(spidev_class)) {
                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
-                return status;
+                return PTR_ERR(spidev_class);
         }
 
         status = spi_register_driver(&spidev_spi);
         if (status < 0) {
-                class_unregister(&spidev_class);
+                class_destroy(spidev_class);
                 unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
         }
         return status;
@@ -662,7 +666,7 @@ module_init(spidev_init);
 static void __exit spidev_exit(void)
 {
         spi_unregister_driver(&spidev_spi);
-        class_unregister(&spidev_class);
+        class_destroy(spidev_class);
         unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
 }
 module_exit(spidev_exit);