[PATCH] staging: r8188eu: prevent ->Ssid overflow in rtw_wx_set_scan()

[Denis Efremov <denis.e.efremov@oracle.com>]

This code has a check to prevent read overflow but it needs another
check to prevent writing beyond the end of the ->Ssid[] array.

Fixes: 2b42bd58b321 ("staging: r8188eu: introduce new os_dep dir for RTL8188eu driver")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Denis Efremov <denis.e.efremov@oracle.com>
---

This patch is a copy of Dan's 74b6b20df8cf (CVE-2021-28660).
Drivers r8188eu and rtl8188eu share the same code.

 drivers/staging/r8188eu/os_dep/ioctl_linux.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/r8188eu/os_dep/ioctl_linux.c b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
index eb9375b0c660..a2692ce02bc2 100644
--- a/drivers/staging/r8188eu/os_dep/ioctl_linux.c
+++ b/drivers/staging/r8188eu/os_dep/ioctl_linux.c
@@ -1131,9 +1131,11 @@ static int rtw_wx_set_scan(struct net_device *dev, struct iw_request_info *a,
 						break;
 					}
 					sec_len = *(pos++); len -= 1;
-					if (sec_len > 0 && sec_len <= len) {
+					if (sec_len > 0 &&
+					    sec_len <= len &&
+					    sec_len <= 32) {
 						ssid[ssid_index].SsidLength = sec_len;
-						memcpy(ssid[ssid_index].Ssid, pos, ssid[ssid_index].SsidLength);
+						memcpy(ssid[ssid_index].Ssid, pos, sec_len);
 						ssid_index++;
 					}
 					pos += sec_len;
-- 
2.35.3