From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC8F5C433DB for ; Wed, 17 Feb 2021 17:30:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 752A464E45 for ; Wed, 17 Feb 2021 17:30:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230381AbhBQRaW (ORCPT ); Wed, 17 Feb 2021 12:30:22 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:49147 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230364AbhBQRaU (ORCPT ); Wed, 17 Feb 2021 12:30:20 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613582934; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2yNSG/3pQJkBVZWwUooPbXJbbujH8VVlP4gWj5paAq8=; b=imJmkV5UdOye5ir7xLldLC+tQ1pg2b7dhUjanQ01KCtFgtG5robRk701ePww0vgThoAjcN dQ2yP12Ej1ipkugVG9dCZOKc7Y7j68wZswh/AYEUVCpIRiYYIrcgfvnPaUVBXnlLve8QAl f4aENchbZ1nDTYPb2wmmZAgfWHM98sM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-378-ky6kO3knMc680lIH5KE-3A-1; Wed, 17 Feb 2021 12:28:51 -0500 X-MC-Unique: ky6kO3knMc680lIH5KE-3A-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C44A3192CC40; Wed, 17 Feb 2021 17:28:50 +0000 (UTC) Received: from localhost (unknown [10.40.194.27]) by smtp.corp.redhat.com (Postfix) with ESMTP id 572CD5C3E4; Wed, 17 Feb 2021 17:28:50 +0000 (UTC) From: Petr Lautrbach To: SElinux list Cc: Nicolas Iooss , James Carter Subject: Re: [PATCH] libsepol/cil: Destroy disabled optional blocks after pass is complete In-Reply-To: References: <20210208162342.410262-1-jwcart2@gmail.com> Date: Wed, 17 Feb 2021 18:28:49 +0100 Message-ID: <87tuqafvse.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org Nicolas Iooss writes: > On Mon, Feb 8, 2021 at 5:23 PM James Carter wrote: >> >> Nicolas Iooss reports: >> I am continuing to investigate OSS-Fuzz crashes and the following one >> is quite complex. Here is a CIL policy which triggers a >> heap-use-after-free error in the CIL compiler: >> >> (class CLASS (PERM2)) >> (classorder (CLASS)) >> (classpermission CLSPRM) >> (optional o >> (mlsvalidatetrans x (domby l1 h1)) >> (common CLSCOMMON (PERM1)) >> (classcommon CLASS CLSCOMMON) >> ) >> (classpermissionset CLSPRM (CLASS (PERM1))) >> >> The issue is that the mlsvalidatetrans fails to resolve in pass >> CIL_PASS_MISC3, which comes after the resolution of classcommon (in >> pass CIL_PASS_MISC2). So: >> >> * In pass CIL_PASS_MISC2, the optional block still exists, the >> classcommon is resolved and class CLASS is linked with common >> CLSCOMMON. >> * In pass CIL_PASS_MISC3, the optional block is destroyed, including >> the common CLSCOMMON. >> * When classpermissionset is resolved, function cil_resolve_classperms >> uses "common_symtab = &class->common->perms;", which has been freed. >> The use-after-free issue occurs in __cil_resolve_perms (in >> libsepol/cil/src/cil_resolve_ast.c): >> >> // common_symtab was freed >> rc = cil_symtab_get_datum(common_symtab, curr->data, &perm_datum); >> >> The fundamental problem here is that when the optional block is >> disabled it is immediately destroyed in the middle of the pass, so >> the class has not been reset and still refers to the now destroyed >> common when the classpermissionset is resolved later in the same pass. >> >> Added a list, disabled_optionals, to struct cil_args_resolve which is >> passed when resolving the tree. When optionals are disabled, they are >> now added to this list and then are destroyed after the tree has been >> reset between passes. >> >> Reported-by: Nicolas Iooss >> Signed-off-by: James Carter > > I confirm the patch fixes the issue. > > Acked-by: Nicolas Iooss > This is merged now. > Thanks! > Nicolas > >> --- >> libsepol/cil/src/cil_resolve_ast.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/libsepol/cil/src/cil_resolve_ast.c b/libsepol/cil/src/cil_resolve_ast.c >> index 0c85eabe..49a5d139 100644 >> --- a/libsepol/cil/src/cil_resolve_ast.c >> +++ b/libsepol/cil/src/cil_resolve_ast.c >> @@ -51,6 +51,7 @@ struct cil_args_resolve { >> struct cil_db *db; >> enum cil_pass pass; >> uint32_t *changed; >> + struct cil_list *disabled_optionals; >> struct cil_tree_node *optstack; >> struct cil_tree_node *boolif; >> struct cil_tree_node *macro; >> @@ -3863,7 +3864,7 @@ int __cil_resolve_ast_last_child_helper(struct cil_tree_node *current, void *ext >> >> if (((struct cil_optional *)parent->data)->enabled == CIL_FALSE) { >> *(args->changed) = CIL_TRUE; >> - cil_tree_children_destroy(parent); >> + cil_list_append(args->disabled_optionals, CIL_NODE, parent); >> } >> >> /* pop off the stack */ >> @@ -3926,6 +3927,7 @@ int cil_resolve_ast(struct cil_db *db, struct cil_tree_node *current) >> extra_args.in_list = NULL; >> extra_args.blockstack = NULL; >> >> + cil_list_init(&extra_args.disabled_optionals, CIL_NODE); >> cil_list_init(&extra_args.sidorder_lists, CIL_LIST_ITEM); >> cil_list_init(&extra_args.classorder_lists, CIL_LIST_ITEM); >> cil_list_init(&extra_args.unordered_classorder_lists, CIL_LIST_ITEM); >> @@ -3993,6 +3995,7 @@ int cil_resolve_ast(struct cil_db *db, struct cil_tree_node *current) >> } >> >> if (changed && (pass > CIL_PASS_CALL1)) { >> + struct cil_list_item *item; >> /* Need to re-resolve because an optional was disabled that contained >> * one or more declarations. We only need to reset to the call1 pass >> * because things done in the preceding passes aren't allowed in >> @@ -4021,6 +4024,11 @@ int cil_resolve_ast(struct cil_db *db, struct cil_tree_node *current) >> cil_log(CIL_ERR, "Failed to reset declarations\n"); >> goto exit; >> } >> + cil_list_for_each(item, extra_args.disabled_optionals) { >> + cil_tree_children_destroy(item->data); >> + } >> + cil_list_destroy(&extra_args.disabled_optionals, CIL_FALSE); >> + cil_list_init(&extra_args.disabled_optionals, CIL_NODE); >> } >> >> /* reset the arguments */ >> @@ -4049,6 +4057,7 @@ exit: >> __cil_ordered_lists_destroy(&extra_args.catorder_lists); >> __cil_ordered_lists_destroy(&extra_args.sensitivityorder_lists); >> __cil_ordered_lists_destroy(&extra_args.unordered_classorder_lists); >> + cil_list_destroy(&extra_args.disabled_optionals, CIL_FALSE); >> cil_list_destroy(&extra_args.in_list, CIL_FALSE); >> >> return rc; >> -- >> 2.26.2 >>