cifs: escape spaces in share names

Commit 653a5efb ("cifs: update super_operations to show_devname")
introduced the display of devname for cifs mounts. However, when mounting
a share which has a whitespace in the name, that exact share name is also
displayed in mountinfo. Make sure that all whitespace is escaped.
Signed-off-by: Maciek Borzecki <maciek.borzecki@gmail.com>
CC: <stable@vger.kernel.org> # 5.11+
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsfs.c

@@ -476,7 +476,8 @@ static int cifs_show_devname(struct seq_file *m, struct dentry *root)
 		seq_puts(m, "none");
 	else {
 		convert_delimiter(devname, '/');
-		seq_puts(m, devname);
+		/* escape all spaces in share names */
+		seq_escape(m, devname, " \t");
 		kfree(devname);
 	}
 	return 0;