[PATCH] cfg80211: fix wext-compat memory leak

[PATCH] cfg80211: fix wext-compat memory leak

[stefan.seyfried]

From: Stefan Seyfried <seife+kernel@b1-systems.com>

cfg80211_wext_giwrate and sinfo.pertid might allocate sinfo.pertid via
rdev_get_station(), but never release it

Signed-off-by: Stefan Seyfried <seife+kernel@b1-systems.com>
---
 net/wireless/wext-compat.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/wireless/wext-compat.c b/net/wireless/wext-compat.c
index 167f7025ac98..f462336aac1c 100644
--- a/net/wireless/wext-compat.c
+++ b/net/wireless/wext-compat.c
@@ -1277,12 +1277,16 @@ static int cfg80211_wext_giwrate(struct net_device *dev,
 	err = rdev_get_station(rdev, dev, addr, &sinfo);
 	if (err)
 		return err;
-
 	if (!(sinfo.filled & BIT_ULL(NL80211_STA_INFO_TX_BITRATE)))
 		return -EOPNOTSUPP;
 
 	rate->value = 100000 * cfg80211_calculate_bitrate(&sinfo.txrate);
 
+	/* sta_set_sinfo(), called from ieee80211_get_station(), called from
+	 * rdev_get_station via rdev->ops->get_station, allocates pertid struct
+	 * which we do not use here. */
+	kfree(sinfo.pertid);
+
 	return 0;
 }
 
@@ -1293,7 +1297,7 @@ static struct iw_statistics *cfg80211_wireless_stats(struct net_device *dev)
 	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
 	/* we are under RTNL - globally locked - so can use static structs */
 	static struct iw_statistics wstats;
-	static struct station_info sinfo;
+	static struct station_info sinfo = {};
 	u8 bssid[ETH_ALEN];
 
 	if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_STATION)
@@ -1352,6 +1356,9 @@ static struct iw_statistics *cfg80211_wireless_stats(struct net_device *dev)
 	if (sinfo.filled & BIT_ULL(NL80211_STA_INFO_TX_FAILED))
 		wstats.discard.retries = sinfo.tx_failed;
 
+	/* see cfg80211_wext_giwrate() above */
+	kfree(sinfo.pertid);
+
 	return &wstats;
 }
 
-- 
2.19.0

Re: [PATCH] cfg80211: fix wext-compat memory leak

[Johannes Berg]

Hi Stefan,

Thanks for the investigation & fix. I've changed the fix to use
cfg80211_sinfo_release_content(), take care of the error path in
cfg80211_wext_giwrate() and added a Fixes tag :-)

Applied with those changes.

johannes


On Sun, 2018-09-30 at 12:53 +0200, stefan.seyfried@googlemail.com wrote:
> From: Stefan Seyfried <seife+kernel@b1-systems.com>
> 
> cfg80211_wext_giwrate and sinfo.pertid might allocate sinfo.pertid via
> rdev_get_station(), but never release it
> 
> Signed-off-by: Stefan Seyfried <seife+kernel@b1-systems.com>
> ---
>  net/wireless/wext-compat.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/net/wireless/wext-compat.c b/net/wireless/wext-compat.c
> index 167f7025ac98..f462336aac1c 100644
> --- a/net/wireless/wext-compat.c
> +++ b/net/wireless/wext-compat.c
> @@ -1277,12 +1277,16 @@ static int cfg80211_wext_giwrate(struct net_device *dev,
>  	err = rdev_get_station(rdev, dev, addr, &sinfo);
>  	if (err)
>  		return err;
> -
>  	if (!(sinfo.filled & BIT_ULL(NL80211_STA_INFO_TX_BITRATE)))
>  		return -EOPNOTSUPP;
>  
>  	rate->value = 100000 * cfg80211_calculate_bitrate(&sinfo.txrate);
>  
> +	/* sta_set_sinfo(), called from ieee80211_get_station(), called from
> +	 * rdev_get_station via rdev->ops->get_station, allocates pertid struct
> +	 * which we do not use here. */
> +	kfree(sinfo.pertid);
> +
>  	return 0;
>  }
>  
> @@ -1293,7 +1297,7 @@ static struct iw_statistics *cfg80211_wireless_stats(struct net_device *dev)
>  	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
>  	/* we are under RTNL - globally locked - so can use static structs */
>  	static struct iw_statistics wstats;
> -	static struct station_info sinfo;
> +	static struct station_info sinfo = {};
>  	u8 bssid[ETH_ALEN];
>  
>  	if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_STATION)
> @@ -1352,6 +1356,9 @@ static struct iw_statistics *cfg80211_wireless_stats(struct net_device *dev)
>  	if (sinfo.filled & BIT_ULL(NL80211_STA_INFO_TX_FAILED))
>  		wstats.discard.retries = sinfo.tx_failed;
>  
> +	/* see cfg80211_wext_giwrate() above */
> +	kfree(sinfo.pertid);
> +
>  	return &wstats;
>  }
>  

Re: [PATCH] cfg80211: fix wext-compat memory leak

[Stefan Seyfried]

Hi Johannes,

Am 01.10.18 um 09:12 schrieb Johannes Berg:
> Hi Stefan,
> 
> Thanks for the investigation & fix. I've changed the fix to use
> cfg80211_sinfo_release_content(),

Being totally unfamiliar with the code, I was not sure about that :-)

> take care of the error path in
> cfg80211_wext_giwrate() and added a Fixes tag :-)

That's certainly much better.

Thanks!

(kudos to Vlastimil Babka who pointed out trace-cmd to me on the
 opensuse-kernel malinglist, which made the investigation quite easy)
-- 
Stefan Seyfried

"For a successful technology, reality must take precedence over
 public relations, for nature cannot be fooled." -- Richard Feynman