ipw2x00: potential buffer overflow in libipw_wx_set_encodeext()

The "ext->key_len" is a u16 that comes from the user.  If it's over
SCM_KEY_LEN (32) that could lead to memory corruption.

Fixes: e0d369d1 ("[PATCH] ieee82011: Added WE-18 support to default wireless extension handler")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Stanislav Yakovlev <stas.yakovlev@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/YHaoA1i+8uT4ir4h@mwanda

drivers/net/wireless/intel/ipw2x00/libipw_wx.c

@@ -633,8 +633,10 @@ int libipw_wx_set_encodeext(struct libipw_device *ieee,
 	}
 
 	if (ext->alg != IW_ENCODE_ALG_NONE) {
-		memcpy(sec.keys[idx], ext->key, ext->key_len);
-		sec.key_sizes[idx] = ext->key_len;
+		int key_len = clamp_val(ext->key_len, 0, SCM_KEY_LEN);
+
+		memcpy(sec.keys[idx], ext->key, key_len);
+		sec.key_sizes[idx] = key_len;
 		sec.flags |= (1 << idx);
 		if (ext->alg == IW_ENCODE_ALG_WEP) {
 			sec.encode_alg[idx] = SEC_ALG_WEP;