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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 <lrodriguez@atheros.com>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Johannes Berg 2009-03-24 09:35:46 +01:00 committed by John W. Linville
parent 3832c287f1
commit 4bbf4d5658
3 changed files with 33 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
net/wireless/core.c
View File

@ -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<idx> where <idx> 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);
return result;
return 0;
}
/* exported functions */

3
net/wireless/core.h
View File

@ -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.

24
net/wireless/nl80211.c
View File

@ -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();
if (info->attrs[NL80211_ATTR_WIPHY_NAME]) {
mutex_lock(&cfg80211_mutex);
rdev = __cfg80211_drv_from_info(info);
if (IS_ERR(rdev)) {
result = PTR_ERR(rdev);
goto unlock;
}
mutex_lock(&rdev->mtx);
if (info->attrs[NL80211_ATTR_WIPHY_NAME])
result = cfg80211_dev_rename(
rdev, nla_data(info->attrs[NL80211_ATTR_WIPHY_NAME]));
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;
}