smb: client: handle lack of FSCTL_GET_REPARSE_POINT support

As per MS-FSA 2.1.5.10.14, support for FSCTL_GET_REPARSE_POINT is
optional and if the server doesn't support it,
STATUS_INVALID_DEVICE_REQUEST must be returned for the operation.

If we find files with reparse points and we can't read them due to
lack of client or server support, just ignore it and then treat them
as regular files or junctions.

Fixes: 5f71ebc41294 ("smb: client: parse reparse point flag in create response")
Reported-by: Sebastian Steinbeisser <[e-mail]>
Tested-by: Sebastian Steinbeisser <[e-mail]>
Acked-by: Tom Talpey <[e-mail]>
Signed-off-by: Paulo Alcantara (Red Hat) <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/client/inode.c

···
 	}
 
 	rc = -EOPNOTSUPP;
-	switch ((data->reparse.tag = tag)) {
-	case 0: /* SMB1 symlink */
+	data->reparse.tag = tag;
+	if (!data->reparse.tag) {
 		if (server->ops->query_symlink) {
 			rc = server->ops->query_symlink(xid, tcon,
 							cifs_sb, full_path,
 							&data->symlink_target);
+		}
+		if (rc == -EOPNOTSUPP)
+			data->reparse.tag = IO_REPARSE_TAG_INTERNAL;
+	}
+
+	switch (data->reparse.tag) {
+	case 0: /* SMB1 symlink */
+		break;
+	case IO_REPARSE_TAG_INTERNAL:
+		rc = 0;
+		if (le32_to_cpu(data->fi.Attributes) & ATTR_DIRECTORY) {
+			cifs_create_junction_fattr(fattr, sb);
+			goto out;
 		}
 		break;
 	case IO_REPARSE_TAG_MOUNT_POINT:

fs/smb/client/reparse.c

···
 	}
 
 	switch (tag) {
+	case IO_REPARSE_TAG_INTERNAL:
+		if (!(fattr->cf_cifsattrs & ATTR_DIRECTORY))
+			return false;
+		fallthrough;
 	case IO_REPARSE_TAG_DFS:
 	case IO_REPARSE_TAG_DFSR:
 	case IO_REPARSE_TAG_MOUNT_POINT:

fs/smb/client/reparse.h

···
 #include "fs_context.h"
 #include "cifsglob.h"
 
+/*
+ * Used only by cifs.ko to ignore reparse points from files when client or
+ * server doesn't support FSCTL_GET_REPARSE_POINT.
+ */
+#define IO_REPARSE_TAG_INTERNAL ((__u32)~0U)
+
 static inline dev_t reparse_nfs_mkdev(struct reparse_posix_data *buf)
 {
 	u64 v = le64_to_cpu(*(__le64 *)buf->DataBuffer);
···
 static inline bool reparse_inode_match(struct inode *inode,
 				       struct cifs_fattr *fattr)
 {
+	struct cifsInodeInfo *cinode = CIFS_I(inode);
 	struct timespec64 ctime = inode_get_ctime(inode);
 
-	return (CIFS_I(inode)->cifsAttrs & ATTR_REPARSE) &&
-		CIFS_I(inode)->reparse_tag == fattr->cf_cifstag &&
+	/*
+	 * Do not match reparse tags when client or server doesn't support
+	 * FSCTL_GET_REPARSE_POINT.  @fattr->cf_cifstag should contain correct
+	 * reparse tag from query dir response but the client won't be able to
+	 * read the reparse point data anyway.  This spares us a revalidation.
+	 */
+	if (cinode->reparse_tag != IO_REPARSE_TAG_INTERNAL &&
+	    cinode->reparse_tag != fattr->cf_cifstag)
+		return false;
+	return (cinode->cifsAttrs & ATTR_REPARSE) &&
 		timespec64_equal(&ctime, &fattr->cf_ctime);
 }
 

fs/smb/client/smb2inode.c

···
 
 	switch (rc) {
 	case 0:
+		rc = parse_create_response(data, cifs_sb, &out_iov[0]);
+		break;
 	case -EOPNOTSUPP:
 		/*
 		 * BB TODO: When support for special files added to Samba