From 4bbf4d56583dd52c429d88f43cb614bdbe5deea6 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Tue, 24 Mar 2009 09:35:46 +0100 Subject: [PATCH] cfg80211: fix locking in nl80211_set_wiphy Luis reports that there's a circular locking dependency; this is because cfg80211_dev_rename() will acquire the cfg80211_mutex while the device mutex is held, while this normally is done the other way around. The solution is to open-code the device-getting in nl80211_set_wiphy and require holding the mutex around cfg80211_dev_rename rather than acquiring it within. Also fix a bug -- rtnl locking is expected by drivers so we need to provide it. Reported-by: Luis R. Rodriguez Signed-off-by: Johannes Berg Signed-off-by: John W. Linville --- net/wireless/core.c | 30 ++++++++++-------------------- net/wireless/core.h | 3 +++ net/wireless/nl80211.c | 28 ++++++++++++++++++++-------- 3 files changed, 33 insertions(+), 28 deletions(-) diff --git a/net/wireless/core.c b/net/wireless/core.c index 17fe3904974..d1f556535f6 100644 --- a/net/wireless/core.c +++ b/net/wireless/core.c @@ -87,7 +87,7 @@ struct wiphy *wiphy_idx_to_wiphy(int wiphy_idx) } /* requires cfg80211_mutex to be held! */ -static struct cfg80211_registered_device * +struct cfg80211_registered_device * __cfg80211_drv_from_info(struct genl_info *info) { int ifindex; @@ -176,13 +176,14 @@ void cfg80211_put_dev(struct cfg80211_registered_device *drv) mutex_unlock(&drv->mtx); } +/* requires cfg80211_mutex to be held */ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev, char *newname) { struct cfg80211_registered_device *drv; int wiphy_idx, taken = -1, result, digits; - mutex_lock(&cfg80211_mutex); + assert_cfg80211_lock(); /* prohibit calling the thing phy%d when %d is not its number */ sscanf(newname, PHY_NAME "%d%n", &wiphy_idx, &taken); @@ -195,30 +196,23 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev, * deny the name if it is phy where is printed * without leading zeroes. taken == strlen(newname) here */ - result = -EINVAL; if (taken == strlen(PHY_NAME) + digits) - goto out_unlock; + return -EINVAL; } /* Ignore nop renames */ - result = 0; if (strcmp(newname, dev_name(&rdev->wiphy.dev)) == 0) - goto out_unlock; + return 0; /* Ensure another device does not already have this name. */ - list_for_each_entry(drv, &cfg80211_drv_list, list) { - result = -EINVAL; + list_for_each_entry(drv, &cfg80211_drv_list, list) if (strcmp(newname, dev_name(&drv->wiphy.dev)) == 0) - goto out_unlock; - } + return -EINVAL; - /* this will only check for collisions in sysfs - * which is not even always compiled in. - */ result = device_rename(&rdev->wiphy.dev, newname); if (result) - goto out_unlock; + return result; if (rdev->wiphy.debugfsdir && !debugfs_rename(rdev->wiphy.debugfsdir->d_parent, @@ -228,13 +222,9 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev, printk(KERN_ERR "cfg80211: failed to rename debugfs dir to %s!\n", newname); - result = 0; -out_unlock: - mutex_unlock(&cfg80211_mutex); - if (result == 0) - nl80211_notify_dev_rename(rdev); + nl80211_notify_dev_rename(rdev); - return result; + return 0; } /* exported functions */ diff --git a/net/wireless/core.h b/net/wireless/core.h index 97a6fd8b2b0..d43daa236ef 100644 --- a/net/wireless/core.h +++ b/net/wireless/core.h @@ -99,6 +99,9 @@ struct cfg80211_internal_bss { struct cfg80211_registered_device *cfg80211_drv_by_wiphy_idx(int wiphy_idx); int get_wiphy_idx(struct wiphy *wiphy); +struct cfg80211_registered_device * +__cfg80211_drv_from_info(struct genl_info *info); + /* * This function returns a pointer to the driver * that the genl_info item that is passed refers to. diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c index 8808431bd58..353e1a4ece8 100644 --- a/net/wireless/nl80211.c +++ b/net/wireless/nl80211.c @@ -366,16 +366,26 @@ static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info) int result = 0, rem_txq_params = 0; struct nlattr *nl_txq_params; - rdev = cfg80211_get_dev_from_info(info); - if (IS_ERR(rdev)) - return PTR_ERR(rdev); + rtnl_lock(); + + mutex_lock(&cfg80211_mutex); + + rdev = __cfg80211_drv_from_info(info); + if (IS_ERR(rdev)) { + result = PTR_ERR(rdev); + goto unlock; + } - if (info->attrs[NL80211_ATTR_WIPHY_NAME]) { + mutex_lock(&rdev->mtx); + + if (info->attrs[NL80211_ATTR_WIPHY_NAME]) result = cfg80211_dev_rename( rdev, nla_data(info->attrs[NL80211_ATTR_WIPHY_NAME])); - if (result) - goto bad_res; - } + + mutex_unlock(&cfg80211_mutex); + + if (result) + goto bad_res; if (info->attrs[NL80211_ATTR_WIPHY_TXQ_PARAMS]) { struct ieee80211_txq_params txq_params; @@ -471,7 +481,9 @@ static int nl80211_set_wiphy(struct sk_buff *skb, struct genl_info *info) bad_res: - cfg80211_put_dev(rdev); + mutex_unlock(&rdev->mtx); + unlock: + rtnl_unlock(); return result; } -- 2.41.1