From patchwork Thu May 26 13:25:05 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pablo Neira Ayuso X-Patchwork-Id: 1635855 X-Patchwork-Delegate: pablo@netfilter.org Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=2620:137:e000::1:20; helo=out1.vger.email; envelope-from=netfilter-devel-owner@vger.kernel.org; receiver=) Received: from out1.vger.email (out1.vger.email [IPv6:2620:137:e000::1:20]) by bilbo.ozlabs.org (Postfix) with ESMTP id 4L87wF3bYKz9s07 for ; Thu, 26 May 2022 23:25:17 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243062AbiEZNZP (ORCPT ); Thu, 26 May 2022 09:25:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233189AbiEZNZO (ORCPT ); Thu, 26 May 2022 09:25:14 -0400 Received: from mail.netfilter.org (mail.netfilter.org [217.70.188.207]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C5FCFD809D for ; Thu, 26 May 2022 06:25:11 -0700 (PDT) From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: edg-e@nccgroup.com Subject: [PATCH nf,v2] netfilter: nf_tables: disallow non-stateful expression in sets earlier Date: Thu, 26 May 2022 15:25:05 +0200 Message-Id: <20220526132505.308369-1-pablo@netfilter.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Since 3e135cd499bf ("netfilter: nft_dynset: dynamic stateful expression instantiation"), it is possible to attach stateful expressions to set elements. cd5125d8f518 ("netfilter: nf_tables: split set destruction in deactivate and destroy phase") introduces conditional destruction on the object to accomodate transaction semantics. nft_expr_init() calls expr->ops->init() first, then check for NFT_STATEFUL_EXPR, this stills allows to initialize a non-stateful lookup expressions which points to a set, which might lead to UAF since the set is not properly detached from the set->binding for this case. Anyway, this combination is non-sense from nf_tables perspective. This patch fixes this problem by checking for NFT_STATEFUL_EXPR before expr->ops->init() is called. The reporter provides a KASAN splat and a poc reproducer (similar to those autogenerated by syzbot to report use-after-free errors). It is unknown to me if they are using syzbot or if they use similar automated tool to locate the bug that they are reporting. For the record, this is the KASAN splat. [ 85.431824] ================================================================== [ 85.432901] BUG: KASAN: use-after-free in nf_tables_bind_set+0x81b/0xa20 [ 85.433825] Write of size 8 at addr ffff8880286f0e98 by task poc/776 [ 85.434756] [ 85.434999] CPU: 1 PID: 776 Comm: poc Tainted: G W 5.18.0+ #2 [ 85.436023] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 Fixes: 0b2d8a7b638b ("netfilter: nf_tables: add helper functions for expression handling") Reported-and-tested-by: edg-e Signed-off-by: Pablo Neira Ayuso --- v2: fix kbuild report. net/netfilter/nf_tables_api.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index a096b9fbbbdf..93fd7c5c5f7f 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -2873,27 +2873,31 @@ static struct nft_expr *nft_expr_init(const struct nft_ctx *ctx, err = nf_tables_expr_parse(ctx, nla, &expr_info); if (err < 0) - goto err1; + goto err_expr_parse; + + err = -EOPNOTSUPP; + if (!(expr_info.ops->type->flags & NFT_EXPR_STATEFUL)) + goto err_expr_stateful; err = -ENOMEM; expr = kzalloc(expr_info.ops->size, GFP_KERNEL_ACCOUNT); if (expr == NULL) - goto err2; + goto err_expr_stateful; err = nf_tables_newexpr(ctx, &expr_info, expr); if (err < 0) - goto err3; + goto err_expr_new; return expr; -err3: +err_expr_new: kfree(expr); -err2: +err_expr_stateful: owner = expr_info.ops->type->owner; if (expr_info.ops->type->release_ops) expr_info.ops->type->release_ops(expr_info.ops); module_put(owner); -err1: +err_expr_parse: return ERR_PTR(err); } @@ -5413,9 +5417,6 @@ struct nft_expr *nft_set_elem_expr_alloc(const struct nft_ctx *ctx, return expr; err = -EOPNOTSUPP; - if (!(expr->ops->type->flags & NFT_EXPR_STATEFUL)) - goto err_set_elem_expr; - if (expr->ops->type->flags & NFT_EXPR_GC) { if (set->flags & NFT_SET_TIMEOUT) goto err_set_elem_expr;