cifs: fix workstation_name for multiuser mounts

Set workstation_name from the master_tcon for multiuser mounts.

Just in case, protect size_of_ntlmssp_blob against a NULL workstation_name.

Fixes: 49bd49f9 ("cifs: send workstation name during ntlmssp session setup")
Cc: stable@vger.kernel.org # 5.16
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Ryan Bair <ryandbair@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/connect.c

@@ -1977,6 +1977,19 @@ cifs_set_cifscreds(struct smb3_fs_context *ctx, struct cifs_ses *ses)
 		}
 	}
 
+	ctx->workstation_name = kstrdup(ses->workstation_name, GFP_KERNEL);
+	if (!ctx->workstation_name) {
+		cifs_dbg(FYI, "Unable to allocate memory for workstation_name\n");
+		rc = -ENOMEM;
+		kfree(ctx->username);
+		ctx->username = NULL;
+		kfree_sensitive(ctx->password);
+		ctx->password = NULL;
+		kfree(ctx->domainname);
+		ctx->domainname = NULL;
+		goto out_key_put;
+	}
+
 out_key_put:
 	up_read(&key->sem);
 	key_put(key);

fs/cifs/sess.c

@@ -713,7 +713,11 @@ static int size_of_ntlmssp_blob(struct cifs_ses *ses, int base_size)
 	else
 		sz += sizeof(__le16);
 
-	sz += sizeof(__le16) * strnlen(ses->workstation_name, CIFS_MAX_WORKSTATION_LEN);
+	if (ses->workstation_name)
+		sz += sizeof(__le16) * strnlen(ses->workstation_name,
+			CIFS_MAX_WORKSTATION_LEN);
+	else
+		sz += sizeof(__le16);
 
 	return sz;
 }