wifi: cfg80211: wext: add extra SIOCSIWSCAN data check

In 'cfg80211_wext_siwscan()', add extra check whether number of
channels passed via 'ioctl(sock, SIOCSIWSCAN, ...)' doesn't exceed
IW_MAX_FREQUENCIES and reject invalid request with -EINVAL otherwise.

Reported-by: syzbot+253cd2d2491df77c93ac@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=253cd2d2491df77c93acSigned-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Link: https://msgid.link/20240531032010.451295-1-dmantipov@yandex.ruSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/scan.c

@@ -3416,10 +3416,14 @@ int cfg80211_wext_siwscan(struct net_device *dev,
 	wiphy = &rdev->wiphy;
 
 	/* Determine number of channels, needed to allocate creq */
-	if (wreq && wreq->num_channels)
+	if (wreq && wreq->num_channels) {
+		/* Passed from userspace so should be checked */
+		if (unlikely(wreq->num_channels > IW_MAX_FREQUENCIES))
+			return -EINVAL;
 		n_channels = wreq->num_channels;
-	else
+	} else {
 		n_channels = ieee80211_get_num_supported_channels(wiphy);
+	}
 
 	creq = kzalloc(sizeof(*creq) + sizeof(struct cfg80211_ssid) +
 		       n_channels * sizeof(void *),