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Subject[PATCH 4.19 57/93] cfg80211: wext: avoid copying malformed SSIDs
Date
From: Will Deacon <will@kernel.org>

commit 4ac2813cc867ae563a1ba5a9414bfb554e5796fa upstream.

Ensure the SSID element is bounds-checked prior to invoking memcpy()
with its length field, when copying to userspace.

Cc: <stable@vger.kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Reported-by: Nicolas Waisman <nico@semmle.com>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20191004095132.15777-2-will@kernel.org
[adjust commit log a bit]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/wireless/wext-sme.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/net/wireless/wext-sme.c
+++ b/net/wireless/wext-sme.c
@@ -202,6 +202,7 @@ int cfg80211_mgd_wext_giwessid(struct ne
struct iw_point *data, char *ssid)
{
struct wireless_dev *wdev = dev->ieee80211_ptr;
+ int ret = 0;

/* call only for station! */
if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION))
@@ -219,7 +220,10 @@ int cfg80211_mgd_wext_giwessid(struct ne
if (ie) {
data->flags = 1;
data->length = ie[1];
- memcpy(ssid, ie + 2, data->length);
+ if (data->length > IW_ESSID_MAX_SIZE)
+ ret = -EINVAL;
+ else
+ memcpy(ssid, ie + 2, data->length);
}
rcu_read_unlock();
} else if (wdev->wext.connect.ssid && wdev->wext.connect.ssid_len) {
@@ -229,7 +233,7 @@ int cfg80211_mgd_wext_giwessid(struct ne
}
wdev_unlock(wdev);

- return 0;
+ return ret;
}

int cfg80211_mgd_wext_siwap(struct net_device *dev,

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