From 4ac2813cc867ae563a1ba5a9414bfb554e5796fa Mon Sep 17 00:00:00 2001
From: Will Deacon <will@kernel.org>
Date: Fri, 4 Oct 2019 10:51:32 +0100
Subject: [PATCH] cfg80211: wext: avoid copying malformed SSIDs
Git-commit: 4ac2813cc867ae563a1ba5a9414bfb554e5796fa
Patch-mainline: v5.4-rc4
References: jsc#SLE-13430 bsc#1153158 CVE-2019-17133 bnc#1151927

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

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

diff --git a/net/wireless/wext-sme.c b/net/wireless/wext-sme.c
index c67d7a82ab13..73fd0eae08ca 100644
--- a/net/wireless/wext-sme.c
+++ b/net/wireless/wext-sme.c
@@ -202,6 +202,7 @@ int cfg80211_mgd_wext_giwessid(struct net_device *dev,
 			       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 net_device *dev,
 		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 net_device *dev,
 	}
 	wdev_unlock(wdev);
 
-	return 0;
+	return ret;
 }
 
 int cfg80211_mgd_wext_siwap(struct net_device *dev,
-- 
2.16.4