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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 7FBC3C433ED for ; Sun, 4 Apr 2021 02:38:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4014E61243 for ; Sun, 4 Apr 2021 02:38:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236655AbhDDCii (ORCPT ); Sat, 3 Apr 2021 22:38:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58814 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236618AbhDDCii (ORCPT ); Sat, 3 Apr 2021 22:38:38 -0400 Received: from zeniv-ca.linux.org.uk (zeniv-ca.linux.org.uk [IPv6:2607:5300:60:148a::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B660CC061756; Sat, 3 Apr 2021 19:38:34 -0700 (PDT) Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94 #2 (Red Hat Linux)) id 1lSsek-002NjV-B3; Sun, 04 Apr 2021 02:38:30 +0000 Date: Sun, 4 Apr 2021 02:38:30 +0000 From: Al Viro To: Christian Brauner Cc: Jens Axboe , syzbot , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, io-uring@vger.kernel.org Subject: Re: [syzbot] WARNING in mntput_no_expire (2) Message-ID: References: <0000000000003a565e05bee596f2@google.com> <20210401154515.k24qdd2lzhtneu47@wittgenstein> <90e7e339-eaec-adb2-cfed-6dc058a117a3@kernel.dk> <20210401174613.vymhhrfsemypougv@wittgenstein> <20210401175919.jpiylhfrlb4xb67u@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Sun, Apr 04, 2021 at 02:34:08AM +0000, Al Viro wrote: > I really wonder what mount is it happening to. BTW, how painful would > it be to teach syzcaller to turn those cascades of > NONFAILING(*(uint8_t*)0x20000080 = 0x12); > NONFAILING(*(uint8_t*)0x20000081 = 0); > NONFAILING(*(uint16_t*)0x20000082 = 0); > NONFAILING(*(uint32_t*)0x20000084 = 0xffffff9c); > NONFAILING(*(uint64_t*)0x20000088 = 0); > NONFAILING(*(uint64_t*)0x20000090 = 0x20000180); > NONFAILING(memcpy((void*)0x20000180, "./file0\000", 8)); > NONFAILING(*(uint32_t*)0x20000098 = 0); > NONFAILING(*(uint32_t*)0x2000009c = 0x80); > NONFAILING(*(uint64_t*)0x200000a0 = 0x23456); > .... > NONFAILING(syz_io_uring_submit(r[1], r[2], 0x20000080, 0)); > into something more readable? Bloody annoyance every time... Sure, I can > manually translate it into > struct io_uring_sqe *sqe = (void *)0x20000080; > char *s = (void *)0x20000180; > memset(sqe, '\0', sizeof(*sqe)); > sqe->opcode = 0x12; // IORING_OP_OPENAT? > sqe->fd = -100; // AT_FDCWD? > sqe->addr = s; > strcpy(s, "./file0"); > sqe->open_flags = 0x80; // O_EXCL??? > sqe->user_data = 0x23456; // random tag? > syz_io_uring_submit(r[1], r[2], (unsigned long)p, 0); > but it's really annoying as hell, especially since syz_io_uring_submit() > comes from syzcaller and the damn thing _knows_ that the third argument > is sodding io_uring_sqe, and never passed to anything other than > memcpy() in there, at that, so the exact address can't matter. ... especially since the native syzcaller reproducer clearly *does* have that information. Simply putting that into comments side-by-side with what gets put into C reproducer would be nice, especially if it goes with field names...