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 Received: from lists.zx2c4.com (lists.zx2c4.com [165.227.139.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5EC66C7EE23 for ; Tue, 23 May 2023 17:04:39 +0000 (UTC) Received: by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 5ccfe1a0; Tue, 23 May 2023 17:01:41 +0000 (UTC) Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTPS id fe59ecf8 (TLSv1.2:ECDHE-ECDSA-AES256-GCM-SHA384:256:NO) for ; Tue, 23 May 2023 17:01:39 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E9E4C634C7; Tue, 23 May 2023 17:01:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BB37C433D2; Tue, 23 May 2023 17:01:36 +0000 (UTC) Authentication-Results: smtp.kernel.org; dkim=pass (1024-bit key) header.d=zx2c4.com header.i=@zx2c4.com header.b="jAEDfDfm" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zx2c4.com; s=20210105; t=1684861293; 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=lAAodiyGWsaT6Idtby9CZIckSp/ylQBdaFt1VWfkThI=; b=jAEDfDfmf8BHdnZsb8HAiQ2DXBfHNn0zo6txVrJOmcDe8gAWG+0XwNg/Bdh1NQ9pL4HM/9 VBC8cgXnMBgQoduzDaAtNUrQMAt9z6ZDOM3EclU+O5iy9lpm5jclnUtbBdp69bi4yCs3PY CGzKmA6kh/JJlTdI9Nzy40hrMT/0oHw= Received: by mail.zx2c4.com (ZX2C4 Mail Server) with ESMTPSA id 276351ad (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Tue, 23 May 2023 17:01:33 +0000 (UTC) Date: Tue, 23 May 2023 19:01:31 +0200 From: "Jason A. Donenfeld" To: Jakub Kicinski Cc: Eric Dumazet , syzbot , netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, davem@davemloft.net, linux-kernel@vger.kernel.org, pabeni@redhat.com, wireguard@lists.zx2c4.com, jann@thejh.net Subject: Re: [syzbot] [wireguard?] KASAN: slab-use-after-free Write in enqueue_timer Message-ID: References: <000000000000c0b11d05fa917fe3@google.com> <20230523090512.19ca60b6@kernel.org> <20230523094108.0c624d47@kernel.org> <20230523094736.3a9f6f8c@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230523094736.3a9f6f8c@kernel.org> X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" On Tue, May 23, 2023 at 09:47:36AM -0700, Jakub Kicinski wrote: > On Tue, 23 May 2023 18:42:53 +0200 Jason A. Donenfeld wrote: > > > It should, no idea why it isn't. Looking thru the code now I don't see > > > any obvious gaps where timer object is on a list but not active :S > > > There's no way to get a vmcore from syzbot, right? :) > > > > > > Also I thought the shutdown leads to a warning when someone tries to > > > schedule the dead timer but in fact add_timer() just exits cleanly. > > > So the shutdown won't help us find the culprit :( > > > > Worth noting that it could also be caused by adding to a dead timer > > anywhere in priv_data of another netdev, not just the sole timer_list > > in net_device. > > Oh, I thought you zero'ed in on the watchdog based on offsets. > Still, object debug should track all timers in the slab and complain > on the free path. No, I mentioned watchdog because it's the only timer_list in struct net_device. Offset analysis is an interesting idea though. Look at this: > The buggy address belongs to the object at ffff88801ecc0000 > which belongs to the cache kmalloc-cg-8k of size 8192 > The buggy address is located 5376 bytes inside of > freed 8192-byte region [ffff88801ecc0000, ffff88801ecc2000) IDA says that for syzkaller's vmlinux, net_device has a size of 0xc80 and wg_device has a size of 0x880. 0xc80+0x880=5376. Coincidence that the address offset is just after what wg uses? Hm. Jason