[PATCH 3.16 126/129] mwifiex: Fix possible buffer overflows at parsing bss descriptor

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@xxxxxxx>

commit 13ec7f10b87f5fc04c4ccbd491c94c7980236a74 upstream.

mwifiex_update_bss_desc_with_ie() calls memcpy() unconditionally in
a couple places without checking the destination size.  Since the
source is given from user-space, this may trigger a heap buffer
overflow.

Fix it by putting the length check before performing memcpy().

This fix addresses CVE-2019-3846.

Reported-by: huangwen <huangwen@xxxxxxxxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/wireless/mwifiex/scan.c | 4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/net/wireless/mwifiex/scan.c
+++ b/drivers/net/wireless/mwifiex/scan.c
@@ -1171,6 +1171,8 @@ int mwifiex_update_bss_desc_with_ie(stru
 		}
 		switch (element_id) {
 		case WLAN_EID_SSID:
+			if (element_len > IEEE80211_MAX_SSID_LEN)
+				return -EINVAL;
 			bss_entry->ssid.ssid_len = element_len;
 			memcpy(bss_entry->ssid.ssid, (current_ptr + 2),
 			       element_len);
@@ -1180,6 +1182,8 @@ int mwifiex_update_bss_desc_with_ie(stru
 			break;
 
 		case WLAN_EID_SUPP_RATES:
+			if (element_len > MWIFIEX_SUPPORTED_RATES)
+				return -EINVAL;
 			memcpy(bss_entry->data_rates, current_ptr + 2,
 			       element_len);
 			memcpy(bss_entry->supported_rates, current_ptr + 2,