ksmbd: fix out of bounds in smb3_decrypt_req()

smb3_decrypt_req() validate if pdu_length is smaller than
smb2_transform_hdr size.

Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-21589
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/smb2pdu.c

@@ -8614,7 +8614,8 @@ int smb3_decrypt_req(struct ksmbd_work *work)
 	struct smb2_transform_hdr *tr_hdr = smb2_get_msg(buf);
 	int rc = 0;
 
-	if (buf_data_size < sizeof(struct smb2_hdr)) {
+	if (pdu_length < sizeof(struct smb2_transform_hdr) ||
+	    buf_data_size < sizeof(struct smb2_hdr)) {
 		pr_err("Transform message is too small (%u)\n",
 		       pdu_length);
 		return -ECONNABORTED;