UBUNTU: SAUCE: vfs: test that one given mount param is not larger tha…

…n PAGE_SIZE

In order to avoid potential overflows, test that one given mount parameter
is not larger than PAGE_SIZE when parsing it through legacy_parse_param.

Suggested-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
CVE-2022-0185
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Acked-by: Ben Romer <ben.romer@canonical.com>

fs/fs_context.c

@@ -548,7 +548,7 @@ static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
 			      param->key);
 	}
 
-	if (size + len + 2 > PAGE_SIZE)
+	if (len > PAGE_SIZE || size + len + 2 > PAGE_SIZE)
 		return invalf(fc, "VFS: Legacy: Cumulative options too large");
 	if (strchr(param->key, ',') ||
 	    (param->type == fs_value_is_string &&