Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932211AbcKNCQs (ORCPT ); Sun, 13 Nov 2016 21:16:48 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45171 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751982AbcKNCGL (ORCPT ); Sun, 13 Nov 2016 21:06:11 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Vegard Nossum" , "Takashi Iwai" Date: Mon, 14 Nov 2016 00:14:07 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 087/152] ALSA: timer: fix division by zero after SNDRV_TIMER_IOCTL_CONTINUE In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4298 Lines: 87 3.2.84-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Vegard Nossum commit 6b760bb2c63a9e322c0e4a0b5daf335ad93d5a33 upstream. I got this: divide error: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 1327 Comm: a.out Not tainted 4.8.0-rc2+ #189 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014 task: ffff8801120a9580 task.stack: ffff8801120b0000 RIP: 0010:[] [] snd_hrtimer_callback+0x1da/0x3f0 RSP: 0018:ffff88011aa87da8 EFLAGS: 00010006 RAX: 0000000000004f76 RBX: ffff880112655e88 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff880112655ea0 RDI: 0000000000000001 RBP: ffff88011aa87e00 R08: ffff88013fff905c R09: ffff88013fff9048 R10: ffff88013fff9050 R11: 00000001050a7b8c R12: ffff880114778a00 R13: ffff880114778ab4 R14: ffff880114778b30 R15: 0000000000000000 FS: 00007f071647c700(0000) GS:ffff88011aa80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000603001 CR3: 0000000112021000 CR4: 00000000000006e0 Stack: 0000000000000000 ffff880114778ab8 ffff880112655ea0 0000000000004f76 ffff880112655ec8 ffff880112655e80 ffff880112655e88 ffff88011aa98fc0 00000000b97ccf2b dffffc0000000000 ffff88011aa98fc0 ffff88011aa87ef0 Call Trace: [] __hrtimer_run_queues+0x347/0xa00 [] ? snd_hrtimer_close+0x130/0x130 [] ? retrigger_next_event+0x1b0/0x1b0 [] ? hrtimer_interrupt+0x136/0x4b0 [] hrtimer_interrupt+0x1b0/0x4b0 [] local_apic_timer_interrupt+0x6e/0xf0 [] ? kvm_guest_apic_eoi_write+0x13/0xc0 [] smp_apic_timer_interrupt+0x76/0xa0 [] apic_timer_interrupt+0x8c/0xa0 [] ? _raw_spin_unlock_irqrestore+0x2c/0x60 [] snd_timer_start1+0xdd/0x670 [] snd_timer_continue+0x45/0x80 [] snd_timer_user_ioctl+0x1030/0x2830 [] ? __follow_pte.isra.49+0x430/0x430 [] ? snd_timer_pause+0x80/0x80 [] ? do_wp_page+0x3aa/0x1c90 [] ? handle_mm_fault+0xbc8/0x27f0 [] ? __pmd_alloc+0x370/0x370 [] ? snd_timer_pause+0x80/0x80 [] do_vfs_ioctl+0x193/0x1050 [] ? ioctl_preallocate+0x200/0x200 [] ? syscall_trace_enter+0x3cf/0xdb0 [] ? __context_tracking_exit.part.4+0x9a/0x1e0 [] ? exit_to_usermode_loop+0x190/0x190 [] ? check_preemption_disabled+0x37/0x1e0 [] ? security_file_ioctl+0x89/0xb0 [] SyS_ioctl+0x8f/0xc0 [] ? do_vfs_ioctl+0x1050/0x1050 [] do_syscall_64+0x1c4/0x4e0 [] entry_SYSCALL64_slow_path+0x25/0x25 Code: e8 fc 42 7b fe 8b 0d 06 8a 50 03 49 0f af cf 48 85 c9 0f 88 7c 01 00 00 48 89 4d a8 e8 e0 42 7b fe 48 8b 45 c0 48 8b 4d a8 48 99 <48> f7 f9 49 01 c7 e8 cb 42 7b fe 48 8b 55 d0 48 b8 00 00 00 00 RIP [] snd_hrtimer_callback+0x1da/0x3f0 RSP ---[ end trace 6aa380f756a21074 ]--- The problem happens when you call ioctl(SNDRV_TIMER_IOCTL_CONTINUE) on a completely new/unused timer -- it will have ->sticks == 0, which causes a divide by 0 in snd_hrtimer_callback(). Signed-off-by: Vegard Nossum Signed-off-by: Takashi Iwai Signed-off-by: Ben Hutchings --- sound/core/timer.c | 1 + 1 file changed, 1 insertion(+) --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -822,6 +822,7 @@ int snd_timer_new(struct snd_card *card, timer->tmr_subdevice = tid->subdevice; if (id) strlcpy(timer->id, id, sizeof(timer->id)); + timer->sticks = 1; INIT_LIST_HEAD(&timer->device_list); INIT_LIST_HEAD(&timer->open_list_head); INIT_LIST_HEAD(&timer->active_list_head);