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=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 74618C388F9 for ; Tue, 27 Oct 2020 14:11:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D8B32072D for ; Tue, 27 Oct 2020 14:11:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807861; bh=Noym+lf8cZ47Ly+mv+s8DXWgLUwSiQZUDXTZQt2zu7A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ApUY7PIc/vsd/KqbBJFAeVOoJKwA/bT3YPlwqolmsO6uJLjH7sAZ4P6XGzQY6yB2B kYHvzTHrIaNjnlgWFMVBaj8VsZDxqNvM/8hXmC91BShfm4LeuizASgKO9dpiAzLi0c JWAXTif5bJ6pQMH7NyGJR6ar/55gMBtLV4ahxePA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755364AbgJ0OJh (ORCPT ); Tue, 27 Oct 2020 10:09:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:58832 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2408067AbgJ0OJf (ORCPT ); Tue, 27 Oct 2020 10:09:35 -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 C96F722202; Tue, 27 Oct 2020 14:09:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807775; bh=Noym+lf8cZ47Ly+mv+s8DXWgLUwSiQZUDXTZQt2zu7A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DojXupZvKB6xEY7YGna4lfXsh8b9V1wa+ZeFYXLK7uMTMV1sXXRgj8SsSr2f+MjLA eg/DxhYf2GKDenfjEqgJ4PIW6r6nWVMglK3NRjV5NyrHtfFkvAkAvX+X1VilZlbE5U R0xymkEViWJT7ur2i6ZOb7DyXOP5XfTSKQowOQJc= 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 4.14 006/191] tipc: fix the skb_unshare() in tipc_buf_append() Date: Tue, 27 Oct 2020 14:47:41 +0100 Message-Id: <20201027134910.018656697@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027134909.701581493@linuxfoundation.org> References: <20201027134909.701581493@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;