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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F780C433FE for ; Wed, 5 Oct 2022 18:52:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231202AbiJESwt (ORCPT ); Wed, 5 Oct 2022 14:52:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59462 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231197AbiJESwt (ORCPT ); Wed, 5 Oct 2022 14:52:49 -0400 Received: from smtp-bc08.mail.infomaniak.ch (smtp-bc08.mail.infomaniak.ch [IPv6:2001:1600:4:17::bc08]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4CF96BCC4 for ; Wed, 5 Oct 2022 11:52:45 -0700 (PDT) Received: from smtp-2-0000.mail.infomaniak.ch (unknown [10.5.36.107]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4MjNx70T3gzMqHF5; Wed, 5 Oct 2022 20:52:43 +0200 (CEST) Received: from ns3096276.ip-94-23-54.eu (unknown [23.97.221.149]) by smtp-2-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4MjNx601B0zMppDP; Wed, 5 Oct 2022 20:52:41 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1664995963; bh=vZn9Z/mB+kBdgt4mEB6Y23TDD4U+fH6qbo78+xWpuYQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=pEz4oN7sUYON0JpZHpTERU4Ltbl/WtGBHNpSqWjGPVK8l8YNdVyMRIeRTo1hpURaB VngmfhSZ5C0BY6zGw5Eoca9x5O7vdLovAgH6sZ8LuU6nvDQ3A8rk71zAUt2ztKhd+s JcjdxFQp7+EnVRDjPnd2fSRcqxp57V/gSdfOfun4= Message-ID: Date: Wed, 5 Oct 2022 20:52:41 +0200 MIME-Version: 1.0 User-Agent: Subject: Re: [PATCH v8 4/9] landlock: Support file truncation Content-Language: en-US To: Nathan Chancellor , =?UTF-8?Q?G=c3=bcnther_Noack?= Cc: linux-security-module@vger.kernel.org, James Morris , Paul Moore , "Serge E . Hallyn" , linux-fsdevel@vger.kernel.org, Konstantin Meskhidze References: <20221001154908.49665-1-gnoack3000@gmail.com> <20221001154908.49665-5-gnoack3000@gmail.com> From: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: On 04/10/2022 21:56, Nathan Chancellor wrote: > Hi Günther, > > On Sat, Oct 01, 2022 at 05:49:03PM +0200, Günther Noack wrote: >> Introduce the LANDLOCK_ACCESS_FS_TRUNCATE flag for file truncation. >> >> This flag hooks into the path_truncate LSM hook and covers file >> truncation using truncate(2), ftruncate(2), open(2) with O_TRUNC, as >> well as creat(). >> >> This change also increments the Landlock ABI version, updates >> corresponding selftests, and updates code documentation to document >> the flag. >> >> The following operations are restricted: >> >> open(): requires the LANDLOCK_ACCESS_FS_TRUNCATE right if a file gets >> implicitly truncated as part of the open() (e.g. using O_TRUNC). >> >> Notable special cases: >> * open(..., O_RDONLY|O_TRUNC) can truncate files as well in Linux >> * open() with O_TRUNC does *not* need the TRUNCATE right when it >> creates a new file. >> >> truncate() (on a path): requires the LANDLOCK_ACCESS_FS_TRUNCATE >> right. >> >> ftruncate() (on a file): requires that the file had the TRUNCATE right >> when it was previously opened. >> >> Signed-off-by: Günther Noack > > I just bisected a crash in QEMU with Debian's arm64 configuration to > this change in -next as commit b40deebe7679 ("landlock: Support file > truncation"), which I was able to reproduce like so: Thanks for the report Nathan. I've found an issue in this patch and fixed it in -next with this (rebased) commit: https://git.kernel.org/mic/c/b40deebe7679b05d4852488ef531e189a9621f2e You should already have this update since I pushed it Monday. Please let us know if this fixed the issue. > > $ mkdir -p build/deb > > $ cd build/deb > > $ curl -LSsO http://ftp.us.debian.org/debian/pool/main/l/linux-signed-arm64/linux-image-5.19.0-2-arm64_5.19.11-1_arm64.deb > > $ ar x linux-image-5.19.0-2-arm64_5.19.11-1_arm64.deb > > $ tar xJf data.tar.xz > > $ cp boot/config-5.19.0-2-arm64 ../.config > > $ cd ../.. > > $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- O=build olddefconfig Image.gz > > $ qemu-system-aarch64 \ > -machine virt,gic-version=max,virtualization=true \ > -cpu max,pauth-impdef=true \ > -kernel build/arch/arm64/boot/Image.gz \ > -append "console=ttyAMA0 earlycon" \ > -display none \ > -initrd .../rootfs.cpio \ > -m 512m \ > -nodefaults \ > -no-reboot \ > -serial mon:stdio > ... > [ 0.000000] Linux version 6.0.0-rc7+ (nathan@dev-arch.thelio-3990X) (aarch64-linux-gnu-gcc (GCC) 12.2.0, GNU ld (GNU Binutils) 2.39) #1 SMP Tue Oct 4 12:48:50 MST 2022 > ... > [ 0.518570] Unable to handle kernel paging request at virtual address ffff00000851ff8a > [ 0.518785] Mem abort info: > [ 0.518867] ESR = 0x0000000097c0c061 > [ 0.519001] EC = 0x25: DABT (current EL), IL = 32 bits > [ 0.519155] SET = 0, FnV = 0 > [ 0.519267] EA = 0, S1PTW = 0 > [ 0.519386] FSC = 0x21: alignment fault > [ 0.519524] Data abort info: > [ 0.519615] Access size = 8 byte(s) > [ 0.519722] SSE = 0, SRT = 0 > [ 0.519817] SF = 1, AR = 1 > [ 0.519920] CM = 0, WnR = 1 > [ 0.520040] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000041711000 > [ 0.520225] [ffff00000851ff8a] pgd=180000005fff8003, p4d=180000005fff8003, pud=180000005fff7003, pmd=180000005ffbd003, pte=006800004851ff07 > [ 0.521121] Internal error: Oops: 97c0c061 [#1] SMP > [ 0.521364] Modules linked in: > [ 0.521592] CPU: 0 PID: 9 Comm: kworker/u2:0 Not tainted 6.0.0-rc7+ #1 > [ 0.521863] Hardware name: linux,dummy-virt (DT) > [ 0.522325] Workqueue: events_unbound async_run_entry_fn > [ 0.522973] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > [ 0.523193] pc : apparmor_file_alloc_security+0x98/0x1e0 > [ 0.523431] lr : apparmor_file_alloc_security+0x48/0x1e0 > [ 0.523594] sp : ffff800008093960 > [ 0.523708] x29: ffff800008093960 x28: ffff800008093b30 x27: ffff000002602600 > [ 0.523978] x26: ffffd79796ecf8c0 x25: ffff00000241e705 x24: ffffd79797d98068 > [ 0.524199] x23: ffff00000851ff82 x22: ffff00000851ff80 x21: 0000000000000002 > [ 0.524431] x20: ffffd79796ff5000 x19: ffff00000241ceb0 x18: ffffffffffffffff > [ 0.524647] x17: 000000000000003f x16: ffffd79797678008 x15: 0000000000000000 > [ 0.524850] x14: 0000000000000001 x13: 0000000000000000 x12: 0000000000000006 > [ 0.525087] x11: ffff00001feef940 x10: ffffd7979768f8a0 x9 : ffffd79796c1e51c > [ 0.525325] x8 : ffff00000851ffa0 x7 : 0000000000000000 x6 : 0000000000001e0b > [ 0.525531] x5 : ffff00000851ff80 x4 : ffff800008093990 x3 : ffff000002419700 > [ 0.525745] x2 : 0000000000000001 x1 : ffff00000851ff8a x0 : ffff00000241ceb0 > [ 0.526034] Call trace: > [ 0.526166] apparmor_file_alloc_security+0x98/0x1e0 > [ 0.526424] security_file_alloc+0x6c/0xf0 > [ 0.526570] __alloc_file+0x5c/0xf0 > [ 0.526699] alloc_empty_file+0x68/0x10c > [ 0.526816] path_openat+0x50/0x106c > [ 0.526929] do_filp_open+0x88/0x13c > [ 0.527041] filp_open+0x110/0x1b0 > [ 0.527143] do_name+0xbc/0x230 > [ 0.527256] write_buffer+0x40/0x60 > [ 0.527359] unpack_to_rootfs+0x100/0x2bc > [ 0.527479] do_populate_rootfs+0x70/0x134 > [ 0.527602] async_run_entry_fn+0x40/0x1c0 > [ 0.527723] process_one_work+0x1f4/0x450 > [ 0.527851] worker_thread+0x188/0x4c0 > [ 0.527980] kthread+0xe0/0xe4 > [ 0.528066] ret_from_fork+0x10/0x20 > [ 0.528317] Code: 52800002 d2800000 d2800013 910022e1 (c89ffc20) > [ 0.528736] ---[ end trace 0000000000000000 ]--- > ... > > A rootfs is available at [1] but I don't think it should be necessary > for reproducing this. If there is any additional information I can > provide or patches I can test, I am more than happy to do so! > > [1]: https://github.com/ClangBuiltLinux/boot-utils/raw/bf2fd3500d87f78a914bfc3769b2240f5632e5b9/images/arm64/rootfs.cpio.zst > > Cheers, > Nathan