wireless: Add missing locking to cfg80211_dev_rename

device_rename only performs useful and race free validity
checking at the optional sysfs level so depending on it
for all of the validity checking in cfg80211_dev_rename
is racy.

Instead implement all of the needed validity checking
and locking in cfg80211_dev_rename.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 28 insertions, 5 deletions

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 80afacdae46..f1da0b93bc5 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -143,8 +143,11 @@ void cfg80211_put_dev(struct cfg80211_registered_device *drv)
 int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
                         char *newname)
 {
+        struct cfg80211_registered_device *drv;
         int idx, taken = -1, result, digits;
 
+        mutex_lock(&cfg80211_drv_mutex);
+
         /* prohibit calling the thing phy%d when %d is not its number */
         sscanf(newname, PHY_NAME "%d%n", &idx, &taken);
         if (taken == strlen(newname) && idx != rdev->idx) {
@@ -156,14 +159,30 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
                  * deny the name if it is phy<idx> where <idx> is printed
                  * without leading zeroes. taken == strlen(newname) here
                  */
+                result = -EINVAL;
                 if (taken == strlen(PHY_NAME) + digits)
-                        return -EINVAL;
+                        goto out_unlock;
+        }
+
+
+        /* Ignore nop renames */
+        result = 0;
+        if (strcmp(newname, dev_name(&rdev->wiphy.dev)) == 0)
+                goto out_unlock;
+
+        /* Ensure another device does not already have this name. */
+        list_for_each_entry(drv, &cfg80211_drv_list, list) {
+                result = -EINVAL;
+                if (strcmp(newname, dev_name(&drv->wiphy.dev)) == 0)
+                        goto out_unlock;
         }
 
-        /* this will check for collisions */
+        /* this will only check for collisions in sysfs
+         * which is not even always compiled in.
+         */
         result = device_rename(&rdev->wiphy.dev, newname);
         if (result)
-                return result;
+                goto out_unlock;
 
         if (!debugfs_rename(rdev->wiphy.debugfsdir->d_parent,
                             rdev->wiphy.debugfsdir,
@@ -172,9 +191,13 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
                 printk(KERN_ERR "cfg80211: failed to rename debugfs dir to %s!\n",
                        newname);
 
-        nl80211_notify_dev_rename(rdev);
+        result = 0;
+out_unlock:
+        mutex_unlock(&cfg80211_drv_mutex);
+        if (result == 0)
+                nl80211_notify_dev_rename(rdev);
 
-        return 0;
+        return result;
 }
 
 /* exported functions */