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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 E4001C10F12 for ; Mon, 15 Apr 2019 13:43:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE3AA20684 for ; Mon, 15 Apr 2019 13:43:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727330AbfDONni (ORCPT ); Mon, 15 Apr 2019 09:43:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46682 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725789AbfDONni (ORCPT ); Mon, 15 Apr 2019 09:43:38 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5DB1DF74D8; Mon, 15 Apr 2019 13:43:37 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.38]) by smtp.corp.redhat.com (Postfix) with SMTP id C04AB5C223; Mon, 15 Apr 2019 13:43:32 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 15 Apr 2019 15:43:37 +0200 (CEST) Date: Mon, 15 Apr 2019 15:43:31 +0200 From: Oleg Nesterov To: Casey Schaufler Cc: "chengjian (D)" , neilb@suse.com, Anna.Schumaker@Netapp.com, keescook@chromium.org, "linux-kernel@vger.kernel.org" , viro@zeniv.linux.org.uk, "Xiexiuqi (Xie XiuQi)" , Li Bin , yanaijie@huawei.com, peterz@infradead.org, mingo@redhat.com, Linux Security Module list , selinux@vger.kernel.org Subject: Re: kernel BUG at kernel/cred.c:434! Message-ID: <20190415134331.GC22204@redhat.com> References: <6e4428ca-3da1-a033-08f7-a51e57503989@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 15 Apr 2019 13:43:37 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Well, acct("/proc/self/attr/current") doesn't look like a good idea, but I do not know where should we put the additional check... And probably "echo /proc/self/attr/current > /proc/sys/kernel/core_pattern" can hit the same problem, do_coredump() does override_creds() too. May be just add if (current->cred != current->real_cred) return -EACCES; into proc_pid_attr_write(), I dunno. On 04/12, Casey Schaufler wrote: > > On 4/11/2019 11:21 PM, chengjian (D) wrote: > > Added LSM and SELinux lists. > > > >Hi. > > > > > >syzkaller reported the following BUG: > > > >[   73.146973] kernel BUG at kernel/cred.c:434! > >[   73.150231] invalid opcode: 0000 [#1] SMP KASAN PTI > >[   73.151928] CPU: 2 PID: 4058 Comm: syz-executor.6 Not tainted > >5.1.0-rc4-00062-g2d06b235815e-dirty #2 > >[   73.155174] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > >rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 > >[   73.159798] RIP: 0010:commit_creds+0xadb/0xe50 > >[   73.161426] Code: 8b 5b 20 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f > >8e 06 03 00 00 39 5d 20 0f 85 ff fa ff ff e9 0c fb ff ff e8 05 a2 25 00 > ><0f> 0b 48 c7 c7 80 56 c0 83 e8 95 22 b1 00 e8 f2 a1 25 00 0f 0b 48 > >[   73.167852] RSP: 0000:ffff88836e65f5d0 EFLAGS: 00010293 > >[   73.169636] RAX: ffff8883767b0000 RBX: ffff88837f111300 RCX: > >ffffffff8124b5db > >[   73.171962] RDX: 0000000000000000 RSI: ffffffff83c9b140 RDI: > >ffff88837f111300 > >[   73.174310] RBP: ffff888376610400 R08: 0000000000000000 R09: > >0000000000000004 > >[   73.176646] R10: 0000000000000001 R11: ffffed107c655acf R12: > >ffff8883767b0000 > >[   73.178527] Process accounting resumed > >[   73.179021] R13: ffff88837f111900 R14: ffff88837f111300 R15: > >ffff8883767b0ac0 > >[   73.179029] FS:  00007f2d207f9700(0000) GS:ffff8883e3280000(0000) > >knlGS:0000000000000000 > >[   73.179034] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >[   73.179039] CR2: 00007f1500bd36c0 CR3: 00000003df304003 CR4: > >00000000000206e0 > >[   73.179047] Call Trace: > >[   73.190461]  selinux_setprocattr+0x2ea/0x8f0 > >[   73.191925]  ? ptrace_parent_sid+0x530/0x530 > >[   73.193436]  ? proc_pid_attr_write+0x185/0x5a0 > >[   73.194967]  security_setprocattr+0xa1/0x100 > >[   73.196408]  proc_pid_attr_write+0x307/0x5a0 > >[   73.197869]  ? mem_read+0x40/0x40 > >[   73.199013]  __vfs_write+0x81/0x100 > >[   73.200222]  __kernel_write+0xf8/0x330 > >[   73.201562]  do_acct_process+0xca5/0x1340 > >[   73.202969]  ? __ia32_sys_acct+0x1e0/0x1e0 > >[   73.204498]  ? find_held_lock+0x2f/0x1e0 > >[   73.205857]  ? rcu_irq_exit+0xec/0x2c0 > >[   73.207160]  ? lock_downgrade+0x630/0x630 > >[   73.208541]  acct_pin_kill+0x63/0x150 > >[   73.209816]  pin_kill+0x16d/0x7c0 > >[   73.210934]  ? lockdep_hardirqs_on+0x5e0/0x5e0 > >[   73.212452]  ? xas_start+0x155/0x510 > >[   73.213705]  ? pin_insert+0x50/0x50 > >[   73.214903]  ? finish_wait+0x270/0x270 > >[   73.216213]  ? cpumask_next+0x57/0x90 > >[   73.217442]  ? mnt_pin_kill+0x68/0x1d0 > >[   73.218851]  mnt_pin_kill+0x68/0x1d0 > >[   73.220398]  cleanup_mnt+0x11b/0x150 > >[   73.221970]  task_work_run+0x136/0x1b0 > >[   73.223427]  do_exit+0x830/0x2ca0 > >[   73.224586]  ? trace_hardirqs_off+0x3b/0x180 > >[   73.226088]  ? mm_update_next_owner+0x6a0/0x6a0 > >[   73.227622]  ? find_held_lock+0x2f/0x1e0 > >[   73.228954]  ? get_signal+0x2cf/0x1c00 > >[   73.230236]  ? lock_downgrade+0x630/0x630 > >[   73.231628]  ? rwlock_bug.part.0+0x90/0x90 > >[   73.233020]  do_group_exit+0x106/0x2f0 > >[   73.234330]  get_signal+0x325/0x1c00 > >[   73.235571]  do_signal+0x97/0x1670 > >[   73.236739]  ? do_send_specific+0x12d/0x220 > >[   73.238213]  ? lock_downgrade+0x630/0x630 > >[   73.239566]  ? setup_sigcontext+0x820/0x820 > >[   73.240982]  ? check_kill_permission+0x4a/0x510 > >[   73.242509]  ? do_send_specific+0x156/0x220 > >[   73.243905]  ? do_tkill+0x1c4/0x260 > >[   73.245081]  ? do_send_specific+0x220/0x220 > >[   73.246514]  ? trace_hardirqs_on_thunk+0x1a/0x1c > >[   73.248061]  ? exit_to_usermode_loop+0x97/0x1d0 > >[   73.249619]  exit_to_usermode_loop+0x108/0x1d0 > >[   73.251129]  do_syscall_64+0x461/0x580 > >[   73.252454]  entry_SYSCALL_64_after_hwframe+0x49/0xbe > >[   73.254219] RIP: 0033:0x462eb9 > >[   73.255327] Code: Bad RIP value. > >[   73.256539] RSP: 002b:00007f2d207f8c58 EFLAGS: 00000246 ORIG_RAX: > >00000000000000c8 > >[   73.259454] RAX: 0000000000000000 RBX: 000000000073bf00 RCX: > >0000000000462eb9 > >[   73.262309] RDX: 0000000000000000 RSI: 000000000000001e RDI: > >0000000000000005 > >[   73.265064] RBP: 0000000000000002 R08: 0000000000000000 R09: > >0000000000000000 > >[   73.267774] R10: 0000000000000000 R11: 0000000000000246 R12: > >00007f2d207f96bc > >[   73.270546] R13: 00000000004c5509 R14: 00000000007042f0 R15: > >00000000ffffffff > >[   73.273542] Modules linked in: > >[   73.274670] Dumping ftrace buffer: > >[   73.275852]    (ftrace buffer empty) > >[   73.277187] ---[ end trace dde36a95f458175d ]--- > >[   73.278834] RIP: 0010:commit_creds+0xadb/0xe50 > >[   73.280549] Code: 8b 5b 20 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f > >8e 06 03 00 00 39 5d 20 0f 85 ff fa ff ff e9 0c fb ff ff e8 05 a2 25 00 > ><0f> 0b 48 c7 c7 80 56 c0 83 e8 95 22 b1 00 e8 f2 a1 25 00 0f 0b 48 > >[   73.287090] RSP: 0000:ffff88836e65f5d0 EFLAGS: 00010293 > >[   73.288917] RAX: ffff8883767b0000 RBX: ffff88837f111300 RCX: > >ffffffff8124b5db > >[   73.291390] RDX: 0000000000000000 RSI: ffffffff83c9b140 RDI: > >ffff88837f111300 > >[   73.293864] RBP: ffff888376610400 R08: 0000000000000000 R09: > >0000000000000004 > >[   73.296370] R10: 0000000000000001 R11: ffffed107c655acf R12: > >ffff8883767b0000 > >[   73.299275] R13: ffff88837f111900 R14: ffff88837f111300 R15: > >ffff8883767b0ac0 > >[   73.301351] Process accounting resumed > >[   73.301822] FS:  00007f2d207f9700(0000) GS:ffff8883e3280000(0000) > >knlGS:0000000000000000 > >[   73.301827] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >[   73.301832] CR2: 0000000000462e8f CR3: 0000000003a18002 CR4: > >00000000000206e0 > >[   73.301850] Kernel panic - not syncing: Fatal exception > >[   73.310719] Process accounting resumed > >[   73.311515] Process accounting resumed > >[   73.318916] Dumping ftrace buffer: > >[   73.318921]    (ftrace buffer empty) > >[   73.318945] Kernel Offset: disabled > >[   73.328061] Rebooting in 10 seconds.. > > > > > >425 int commit_creds(struct cred *new) > >426 { > >427         struct task_struct *task = current; > >428         const struct cred *old = task->real_cred; > >429 > >430         kdebug("commit_creds(%p{%d,%d})", new, > >431                atomic_read(&new->usage), > >432                read_cred_subscribers(new)); > >433 > >434         BUG_ON(task->cred != old);  // BUG here > > > > > >I find that the call chain which triggered the BUG is : > > > >do_exit > >    |-=> acct_process > >    |    -=> do_acct_process > >    |        -=> orig_cred = override_creds(file->f_cred); // cred = > >ffff8883c1878900/real_cred = ffff8883c1878900 > >    |        -=>  if (file_start_write_trylock(file)) > >{__kernel_write(file, &ac, sizeof(acct_t), &pos);} > >    |               -=> __kernel_write+0xf8/0x330 > >    |                    -=> __vfs_write+0x81/0x100 > >    |                           -=> proc_pid_attr_write+0x307/0x5a0 > >    |                                -=> security_setprocattr+0xa1/0x100 > >    | -=>selinux_setprocattr+0x2ea/0x8f0 > >    | -=>commit_creds+0xd97/0x1080  // cred = ffff888379a79c00/real_cred = > >ffff888379a79c00 > >    |       -=> revert_creds(orig_cred);   // cred = > >ffff8883c1878900/real_cred = ffff888379a79c00 > >    |-=> task_work_run > >           -=> cleanup_mnt+0x11b/0x150 > >                -=> mnt_pin_kill+0x68/0x1d0 > >                    -=> pin_kill+0x16d/0x7c0 > >                    -=> acct_pin_kill+0x2e/0x100 > >                    -=> do_acct_process+0x1a0/0x1340 > >                          -=> override_creds+0x18a/0x1c0   // cred = > >ffff8883c1878900/real_cred = ffff888379a79c00 > >                          -=>  if (file_start_write_trylock(file)) > >{__kernel_write(file, &ac, sizeof(acct_t), &pos);} > >                                    -=>   ...... > >-=>commit_creds+0xd97/0x1080   // new = ffff888379a6bb00, cred = > >ffff8883c1878900, real_ceed = ffff888379a79c00 BUG here > >                          -=> revert_creds(orig_cred); > > > > > >Syzkaller Report Testcase: > > > >cat crash.log > > > >04:05:28 executing program 3: > >clone(0x24100, 0x0, 0x0, 0x0, 0x0) > >r0 = gettid() > >perf_event_open(&(0x7f00000000c0)={0x2, 0x70, 0x4, 0x2, 0x0, 0x0, 0x0, > >0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, > >0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, > >0x0, 0x0, 0x0, 0x0, @perf_bp={0x0}}, 0x0, 0xffffffffffffffff, > >0xffffffffffffffff, 0x0) > >acct(&(0x7f0000000000)='./file0\x00') > >r1 = openat$smack_thread_current(0xffffffffffffff9c, > >&(0x7f0000000000)='/proc/thread-self/attr/current\x00', 0x2, 0x0) > >fcntl$setown(r1, 0x8, r0) > >rt_tgsigqueueinfo(r0, r0, 0x1e, &(0x7f00000002c0)) > >tkill(r0, 0x1e) > > > > > >Reproduce this BUG: > >./syz-execprog -executor=./syz-executor -repeat=0 -procs=16 -cover=0 > >./crash.log > > > > > >Can anyone help me ? > > > > > >Thanks, > > > >        Cheng Jian. > > > >