Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965218AbcJXP2d (ORCPT ); Mon, 24 Oct 2016 11:28:33 -0400 Received: from mail-wm0-f41.google.com ([74.125.82.41]:37146 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S941031AbcJXP22 (ORCPT ); Mon, 24 Oct 2016 11:28:28 -0400 Subject: Re: BUG: unable to handle kernel NULL pointer dereference at 00000000000001e0 To: Borislav Petkov , linux-serial@vger.kernel.org References: <20161024144831.a4ieul22jck4vwk3@pd.tnic> Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Michael Galbraith From: Jiri Slaby Message-ID: <49489eb2-c7f5-369b-4552-d888cbc27719@suse.cz> Date: Mon, 24 Oct 2016 17:28:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20161024144831.a4ieul22jck4vwk3@pd.tnic> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3362 Lines: 61 On 10/24/2016, 04:48 PM, Borislav Petkov wrote: > Hi people, > > typing "reboot" splats the following on the serial console. Ideas? > > INIT: Sending p[ 427.863916] BUG: unable to handle kernel NULL pointer dereference at 00000000000001e0 > [ 427.885156] IP: [] tty_wakeup+0xc/0x70 > [ 427.898337] PGD 0 [ 427.902051] > [ 427.907498] Oops: 0000 [#1] PREEMPT SMP > [ 427.917635] Modules linked in: nfsv3 nfs_acl nfs fscache lockd sunrpc grace edd af_packet cpufreq_conservative cpufreq_userspace cpufreq_powersave fuse loop md_mod dm_mod joydev hid_generic usbhid ipmi_ssif ohci_pci ohci_hcd ehci_pci ehci_hcd e1000e ptp firewire_ohci edac_core pps_core tpm_infineon sp5100_tco firewire_core acpi_cpufreq serio_raw pcspkr fjes usbcore shpchp edac_mce_amd tpm_tis ipmi_si tpm_tis_core i2c_piix4 k10temp sg ipmi_msghandler tpm sr_mod button cdrom kvm_amd kvm irqbypass crc_itu_t ast ttm drm_kms_helper drm fb_sys_fops sysimgblt sysfillrect syscopyarea i2c_algo_bit scsi_dh_rdac scsi_dh_alua scsi_dh_emc scsi_dh_hp_sw ata_generic pata_atiixp > [ 428.054179] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.0-rc1-1.g73e3f23-default #1 > [ 428.072868] Hardware name: System manufacturer System Product Name/KGP(M)E-D16, BIOS 0902 12/03/2010 > [ 428.094755] task: ffffffffa2c0d500 task.stack: ffffffffa2c00000 > [ 428.109717] RIP: 0010:[] [] tty_wakeup+0xc/0x70 > [ 428.128407] RSP: 0018:ffff9a1a5fc03df8 EFLAGS: 00010086 > [ 428.142184] RAX: ffff9a1857258000 RBX: ffffffffa3050ea0 RCX: 0000000000000000 > [ 428.159649] RDX: 000000000000001b RSI: 0000000000000000 RDI: 0000000000000000 > [ 428.177109] RBP: ffff9a1a5fc03e08 R08: 0000000000000000 R09: 0000000000000000 > [ 428.194547] R10: 0000000000021c77 R11: 0000000000000000 R12: ffff9a1857258000 > [ 428.212002] R13: 0000000000000000 R14: 0000000000000020 R15: 0000000000000020 > [ 428.229481] FS: 0000000000000000(0000) GS:ffff9a1a5fc00000(0000) knlGS:0000000000000000 > [ 428.248938] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 428.263726] CR2: 00000000000001e0 CR3: 0000000390c06000 CR4: 00000000000006f0 > [ 428.281331] Stack: > [ 428.288696] ffffffffa3050ea0 ffff9a1857258000 ffff9a1a5fc03e18 ffffffffa24e0ab1 > [ 428.307064] ffff9a1a5fc03e40 ffffffffa24e8865 ffffffffa3050ea0 00000000000000c2 > [ 428.325456] 0000000000000046 ffff9a1a5fc03e78 ffffffffa24e8a5f ffffffffa3050ea0 > [ 428.343905] Call Trace: > [ 428.352319] [ 428.356216] [] uart_write_wakeup+0x21/0x30 >From the quick look, uart_write_wakeup should now be using refcounting. Does this help (compile-tested only)? --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -106,12 +106,17 @@ static inline struct uart_port *uart_port_check(struct uart_state *state) void uart_write_wakeup(struct uart_port *port) { struct uart_state *state = port->state; + struct tty_struct *ttyp; /* * This means you called this function _after_ the port was * closed. No cookie for you. */ BUG_ON(!state); - tty_wakeup(state->port.tty); + + ttyp = tty_port_tty_get(&state->port); + if (ttyp) + tty_wakeup(ttyp); + tty_kref_put(ttyp); } static void uart_stop(struct tty_struct *tty) thanks, -- js suse labs