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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 830BFC388F9 for ; Tue, 27 Oct 2020 18:02:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 352FE20719 for ; Tue, 27 Oct 2020 18:02:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603821748; bh=Noym+lf8cZ47Ly+mv+s8DXWgLUwSiQZUDXTZQt2zu7A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=wixvdvguQXKJ+Uq8R8yrHpOoD68pVL8Wa4ulFyYUKdnOKq5IwkcI2GJMDsX9LMV65 LxLAbGMGifeuogT6Ff/eXUgA7jAIzTz7cNKIfmqQGz6RfXssVmMhHaun6TDuesULVi wHNGHBcVU82f5YqZ535AfS6sNJNk4ymmmUon4PLU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757583AbgJ0OTt (ORCPT ); Tue, 27 Oct 2020 10:19:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:40432 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757278AbgJ0ORX (ORCPT ); Tue, 27 Oct 2020 10:17:23 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3606C22202; Tue, 27 Oct 2020 14:17:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603808242; bh=Noym+lf8cZ47Ly+mv+s8DXWgLUwSiQZUDXTZQt2zu7A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P8+OQgN5fFf23Nno3WwliRelTVtGEp6YI00DF0/cvxucNBn9lEljiopW5dAHic1Fz KSDJSp4eI7EPLfgsrdF2h5KXFEF0/EyfUq9n8wMQCOCbwY5OjOM8P4bJz7kTJKlmSv rFFbEHOh4CXn2+DllFrCDBdKIa/AtJVkUmezPtRA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jon Maloy , Ying Xue , Cong Wang , Xin Long , Jakub Kicinski , syzbot+e96a7ba46281824cc46a@syzkaller.appspotmail.com Subject: [PATCH 4.19 010/264] tipc: fix the skb_unshare() in tipc_buf_append() Date: Tue, 27 Oct 2020 14:51:08 +0100 Message-Id: <20201027135431.143348471@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135430.632029009@linuxfoundation.org> References: <20201027135430.632029009@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Cong Wang [ Upstream commit ed42989eab57d619667d7e87dfbd8fe207db54fe ] skb_unshare() drops a reference count on the old skb unconditionally, so in the failure case, we end up freeing the skb twice here. And because the skb is allocated in fclone and cloned by caller tipc_msg_reassemble(), the consequence is actually freeing the original skb too, thus triggered the UAF by syzbot. Fix this by replacing this skb_unshare() with skb_cloned()+skb_copy(). Fixes: ff48b6222e65 ("tipc: use skb_unshare() instead in tipc_buf_append()") Reported-and-tested-by: syzbot+e96a7ba46281824cc46a@syzkaller.appspotmail.com Cc: Jon Maloy Cc: Ying Xue Signed-off-by: Cong Wang Reviewed-by: Xin Long Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/tipc/msg.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -140,7 +140,8 @@ int tipc_buf_append(struct sk_buff **hea if (fragid == FIRST_FRAGMENT) { if (unlikely(head)) goto err; - frag = skb_unshare(frag, GFP_ATOMIC); + if (skb_cloned(frag)) + frag = skb_copy(frag, GFP_ATOMIC); if (unlikely(!frag)) goto err; head = *headbuf = frag;