ksmbd: allow a filename to contain special characters on SMB3.1.1 posix extension

If client send SMB2_CREATE_POSIX_CONTEXT to ksmbd, Allow a filename
to contain special characters.

Reported-by: Philipp Kerling <pkerling@casix.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/smb2pdu.c

@@ -2874,7 +2874,7 @@ int smb2_open(struct ksmbd_work *work)
 	int req_op_level = 0, open_flags = 0, may_flags = 0, file_info = 0;
 	int rc = 0;
 	int contxt_cnt = 0, query_disk_id = 0;
-	int maximal_access_ctxt = 0, posix_ctxt = 0;
+	bool maximal_access_ctxt = false, posix_ctxt = false;
 	int s_type = 0;
 	int next_off = 0;
 	char *name = NULL;
@@ -2903,6 +2903,27 @@ int smb2_open(struct ksmbd_work *work)
 		return create_smb2_pipe(work);
 	}
 
+	if (req->CreateContextsOffset && tcon->posix_extensions) {
+		context = smb2_find_context_vals(req, SMB2_CREATE_TAG_POSIX, 16);
+		if (IS_ERR(context)) {
+			rc = PTR_ERR(context);
+			goto err_out2;
+		} else if (context) {
+			struct create_posix *posix = (struct create_posix *)context;
+
+			if (le16_to_cpu(context->DataOffset) +
+				le32_to_cpu(context->DataLength) <
+			    sizeof(struct create_posix) - 4) {
+				rc = -EINVAL;
+				goto err_out2;
+			}
+			ksmbd_debug(SMB, "get posix context\n");
+
+			posix_mode = le32_to_cpu(posix->Mode);
+			posix_ctxt = true;
+		}
+	}
+
 	if (req->NameLength) {
 		name = smb2_get_name((char *)req + le16_to_cpu(req->NameOffset),
 				     le16_to_cpu(req->NameLength),
@@ -2925,9 +2946,11 @@ int smb2_open(struct ksmbd_work *work)
 				goto err_out2;
 		}
 
-		rc = ksmbd_validate_filename(name);
-		if (rc < 0)
-			goto err_out2;
+		if (posix_ctxt == false) {
+			rc = ksmbd_validate_filename(name);
+			if (rc < 0)
+				goto err_out2;
+		}
 
 		if (ksmbd_share_veto_filename(share, name)) {
 			rc = -ENOENT;
@@ -3085,28 +3108,6 @@ int smb2_open(struct ksmbd_work *work)
 			rc = -EBADF;
 			goto err_out2;
 		}
-
-		if (tcon->posix_extensions) {
-			context = smb2_find_context_vals(req,
-							 SMB2_CREATE_TAG_POSIX, 16);
-			if (IS_ERR(context)) {
-				rc = PTR_ERR(context);
-				goto err_out2;
-			} else if (context) {
-				struct create_posix *posix =
-					(struct create_posix *)context;
-				if (le16_to_cpu(context->DataOffset) +
-				    le32_to_cpu(context->DataLength) <
-				    sizeof(struct create_posix) - 4) {
-					rc = -EINVAL;
-					goto err_out2;
-				}
-				ksmbd_debug(SMB, "get posix context\n");
-
-				posix_mode = le32_to_cpu(posix->Mode);
-				posix_ctxt = 1;
-			}
-		}
 	}
 
 	if (ksmbd_override_fsids(work)) {