[ATM]: avoid race conditions related to atm_devs list

Use semaphore to protect atm_devs list, as no one need access to it from
interrupt context.  Avoid race conditions between atm_dev_register(),
atm_dev_lookup() and atm_dev_deregister().  Fix double spin_unlock() bug.

Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Chas Williams <chas@cmf.nrl.navy.mil>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 20 insertions, 23 deletions

diff --git a/net/atm/common.c b/net/atm/common.c
index db9318fc6031..9e016f404e14 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -427,12 +427,12 @@ int vcc_connect(struct socket *sock, int itf, short vpi, int vci)
                 dev = try_then_request_module(atm_dev_lookup(itf), "atm-device-%d", itf);
         } else {
                 dev = NULL;
-                spin_lock(&atm_dev_lock);
+                down(&atm_dev_mutex);
                 if (!list_empty(&atm_devs)) {
                         dev = list_entry(atm_devs.next, struct atm_dev, dev_list);
                         atm_dev_hold(dev);
                 }
-                spin_unlock(&atm_dev_lock);
+                up(&atm_dev_mutex);
         }
         if (!dev)
                 return -ENODEV;
diff --git a/net/atm/resources.c b/net/atm/resources.c
index 35f3ceb76868..ad533b02b84f 100644
--- a/net/atm/resources.c
+++ b/net/atm/resources.c
@@ -25,7 +25,7 @@
 
 
 LIST_HEAD(atm_devs);
-DEFINE_SPINLOCK(atm_dev_lock);
+DECLARE_MUTEX(atm_dev_mutex);
 
 static struct atm_dev *__alloc_atm_dev(const char *type)
 {
@@ -52,7 +52,7 @@ static struct atm_dev *__atm_dev_lookup(int number)
 
         list_for_each(p, &atm_devs) {
                 dev = list_entry(p, struct atm_dev, dev_list);
-                if ((dev->ops) && (dev->number == number)) {
+                if (dev->number == number) {
                         atm_dev_hold(dev);
                         return dev;
                 }
@@ -64,9 +64,9 @@ struct atm_dev *atm_dev_lookup(int number)
 {
         struct atm_dev *dev;
 
-        spin_lock(&atm_dev_lock);
+        down(&atm_dev_mutex);
         dev = __atm_dev_lookup(number);
-        spin_unlock(&atm_dev_lock);
+        up(&atm_dev_mutex);
         return dev;
 }
 
@@ -81,11 +81,11 @@ struct atm_dev *atm_dev_register(const char *type, const struct atmdev_ops *ops,
                     type);
                 return NULL;
         }
-        spin_lock(&atm_dev_lock);
+        down(&atm_dev_mutex);
         if (number != -1) {
                 if ((inuse = __atm_dev_lookup(number))) {
                         atm_dev_put(inuse);
-                        spin_unlock(&atm_dev_lock);
+                        up(&atm_dev_mutex);
                         kfree(dev);
                         return NULL;
                 }
@@ -105,19 +105,17 @@ struct atm_dev *atm_dev_register(const char *type, const struct atmdev_ops *ops,
                 memset(&dev->flags, 0, sizeof(dev->flags));
         memset(&dev->stats, 0, sizeof(dev->stats));
         atomic_set(&dev->refcnt, 1);
-        list_add_tail(&dev->dev_list, &atm_devs);
-        spin_unlock(&atm_dev_lock);
 
         if (atm_proc_dev_register(dev) < 0) {
                 printk(KERN_ERR "atm_dev_register: "
                        "atm_proc_dev_register failed for dev %s\n",
                        type);
-                spin_lock(&atm_dev_lock);
-                list_del(&dev->dev_list);
-                spin_unlock(&atm_dev_lock);
+                up(&atm_dev_mutex);
                 kfree(dev);
                 return NULL;
         }
+        list_add_tail(&dev->dev_list, &atm_devs);
+        up(&atm_dev_mutex);
 
         return dev;
 }
@@ -129,9 +127,9 @@ void atm_dev_deregister(struct atm_dev *dev)
 
         atm_proc_dev_deregister(dev);
 
-        spin_lock(&atm_dev_lock);
+        down(&atm_dev_mutex);
         list_del(&dev->dev_list);
-        spin_unlock(&atm_dev_lock);
+        up(&atm_dev_mutex);
 
         warning_time = jiffies;
         while (atomic_read(&dev->refcnt) != 1) {
@@ -211,16 +209,16 @@ int atm_dev_ioctl(unsigned int cmd, void __user *arg)
                                 return -EFAULT;
                         if (get_user(len, &iobuf->length))
                                 return -EFAULT;
-                        spin_lock(&atm_dev_lock);
+                        down(&atm_dev_mutex);
                         list_for_each(p, &atm_devs)
                                 size += sizeof(int);
                         if (size > len) {
-                                spin_unlock(&atm_dev_lock);
+                                up(&atm_dev_mutex);
                                 return -E2BIG;
                         }
                         tmp_buf = kmalloc(size, GFP_ATOMIC);
                         if (!tmp_buf) {
-                                spin_unlock(&atm_dev_lock);
+                                up(&atm_dev_mutex);
                                 return -ENOMEM;
                         }
                         tmp_p = tmp_buf;
@@ -228,7 +226,7 @@ int atm_dev_ioctl(unsigned int cmd, void __user *arg)
                                 dev = list_entry(p, struct atm_dev, dev_list);
                                 *tmp_p++ = dev->number;
                         }
-                        spin_unlock(&atm_dev_lock);
+                        up(&atm_dev_mutex);
                         error = ((copy_to_user(buf, tmp_buf, size)) ||
                                         put_user(size, &iobuf->length))
                                                 ? -EFAULT : 0;
@@ -415,13 +413,13 @@ static __inline__ void *dev_get_idx(loff_t left)
 
 void *atm_dev_seq_start(struct seq_file *seq, loff_t *pos)
 {
-        spin_lock(&atm_dev_lock);
+        down(&atm_dev_mutex);
         return *pos ? dev_get_idx(*pos) : (void *) 1;
 }
 
 void atm_dev_seq_stop(struct seq_file *seq, void *v)
 {
-        spin_unlock(&atm_dev_lock);
+        up(&atm_dev_mutex);
 }
  
 void *atm_dev_seq_next(struct seq_file *seq, void *v, loff_t *pos)
diff --git a/net/atm/resources.h b/net/atm/resources.h
index 12910619dbb6..b7fb82a93b42 100644
--- a/net/atm/resources.h
+++ b/net/atm/resources.h
@@ -11,8 +11,7 @@
 
 
 extern struct list_head atm_devs;
-extern spinlock_t atm_dev_lock;
-
+extern struct semaphore atm_dev_mutex;
 
 int atm_dev_ioctl(unsigned int cmd, void __user *arg);