From patchwork Tue Oct 27 13:48:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 306861 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 2EE39C55178 for ; Tue, 27 Oct 2020 18:28:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4CD4206E5 for ; Tue, 27 Oct 2020 18:28:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603823307; bh=uN2CxSEDCzGGU6nQ+FvZW9OEUbApARxwXfnsiQR00ms=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=XglArbSViIfhdyi7g+HlfJXBnM+8y3vtmSADKwKRXT1kErc9hNwhThVMK7Z0eKfyU BMxFi2iymMvgAN27cCx2a+9Jv3Pik8BzUSvttFffexkZ33mV4duVlE8p+Bvy8q1VvG yyb8HCMYA0U+urXSRhgrTr0wkx3rGmmQ8Sh9tHeU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S368175AbgJ0N5S (ORCPT ); Tue, 27 Oct 2020 09:57:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:44082 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S368170AbgJ0N5R (ORCPT ); Tue, 27 Oct 2020 09:57:17 -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 D95AF21D41; Tue, 27 Oct 2020 13:57:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603807037; bh=uN2CxSEDCzGGU6nQ+FvZW9OEUbApARxwXfnsiQR00ms=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BkiFCeGJvjdTpudrfNpmQBw275wgjz1hss8WfIci/c0R5sBW89BlpgO37FzCMEvcQ 3ZjvaF2y9sAvXrwn64G+LJMXHYrK52/G6dnxCoO6UiWV1Ce+oJaXMzLbbQAJYjYRUG CfZp8H9L6U8HZxyZNFtXJOUR11K7DztkECW7Rkm0= 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 4.4 002/112] tipc: fix the skb_unshare() in tipc_buf_append() Date: Tue, 27 Oct 2020 14:48:32 +0100 Message-Id: <20201027134900.654163019@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027134900.532249571@linuxfoundation.org> References: <20201027134900.532249571@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -138,7 +138,8 @@ 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;