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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 4971DC43219 for ; Sat, 27 Apr 2019 15:16:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1840C206A3 for ; Sat, 27 Apr 2019 15:16:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728062AbfD0PQT (ORCPT ); Sat, 27 Apr 2019 11:16:19 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:34174 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727667AbfD0PPi (ORCPT ); Sat, 27 Apr 2019 11:15:38 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hKP38-0000zB-Mj; Sat, 27 Apr 2019 16:15:34 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hKP2j-0004Sg-6p; Sat, 27 Apr 2019 16:15:09 +0100 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, Denis Kirjanov , "Adam Jackson" , "Tina Zhang" , "Daniel Vetter" , "Dave Airlie" , "Daniel Vetter" Date: Sat, 27 Apr 2019 16:13:09 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 063/202] drm/modes: Prevent division by zero htotal In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Tina Zhang commit a2fcd5c84f7a7825e028381b10182439067aa90d upstream. This patch prevents division by zero htotal. In a follow-up mail Tina writes: > > How did you manage to get here with htotal == 0? This needs backtraces (or if > > this is just about static checkers, a mention of that). > > -Daniel > > In GVT-g, we are trying to enable a virtual display w/o setting timings for a pipe > (a.k.a htotal=0), then we met the following kernel panic: > > [ 32.832048] divide error: 0000 [#1] SMP PTI > [ 32.833614] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.18.0-rc4-sriov+ #33 > [ 32.834438] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.10.1-0-g8891697-dirty-20180511_165818-tinazhang-linux-1 04/01/2014 > [ 32.835901] RIP: 0010:drm_mode_hsync+0x1e/0x40 > [ 32.836004] Code: 31 c0 c3 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 8b 87 d8 00 00 00 85 c0 75 22 8b 4f 68 85 c9 78 1b 69 47 58 e8 03 00 00 99 f9 b9 d3 4d 62 10 05 f4 01 00 00 f7 e1 89 d0 c1 e8 06 f3 c3 66 > [ 32.836004] RSP: 0000:ffffc900000ebb90 EFLAGS: 00010206 > [ 32.836004] RAX: 0000000000000000 RBX: ffff88001c67c8a0 RCX: 0000000000000000 > [ 32.836004] RDX: 0000000000000000 RSI: ffff88001c67c000 RDI: ffff88001c67c8a0 > [ 32.836004] RBP: ffff88001c7d03a0 R08: ffff88001c67c8a0 R09: ffff88001c7d0330 > [ 32.836004] R10: ffffffff822c3a98 R11: 0000000000000001 R12: ffff88001c67c000 > [ 32.836004] R13: ffff88001c7d0370 R14: ffffffff8207eb78 R15: ffff88001c67c800 > [ 32.836004] FS: 0000000000000000(0000) GS:ffff88001da00000(0000) knlGS:0000000000000000 > [ 32.836004] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 32.836004] CR2: 0000000000000000 CR3: 000000000220a000 CR4: 00000000000006f0 > [ 32.836004] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 32.836004] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 32.836004] Call Trace: > [ 32.836004] intel_mode_from_pipe_config+0x72/0x90 > [ 32.836004] intel_modeset_setup_hw_state+0x569/0xf90 > [ 32.836004] intel_modeset_init+0x905/0x1db0 > [ 32.836004] i915_driver_load+0xb8c/0x1120 > [ 32.836004] i915_pci_probe+0x4d/0xb0 > [ 32.836004] local_pci_probe+0x44/0xa0 > [ 32.836004] ? pci_assign_irq+0x27/0x130 > [ 32.836004] pci_device_probe+0x102/0x1c0 > [ 32.836004] driver_probe_device+0x2b8/0x480 > [ 32.836004] __driver_attach+0x109/0x110 > [ 32.836004] ? driver_probe_device+0x480/0x480 > [ 32.836004] bus_for_each_dev+0x67/0xc0 > [ 32.836004] ? klist_add_tail+0x3b/0x70 > [ 32.836004] bus_add_driver+0x1e8/0x260 > [ 32.836004] driver_register+0x5b/0xe0 > [ 32.836004] ? mipi_dsi_bus_init+0x11/0x11 > [ 32.836004] do_one_initcall+0x4d/0x1eb > [ 32.836004] kernel_init_freeable+0x197/0x237 > [ 32.836004] ? rest_init+0xd0/0xd0 > [ 32.836004] kernel_init+0xa/0x110 > [ 32.836004] ret_from_fork+0x35/0x40 > [ 32.836004] Modules linked in: > [ 32.859183] ---[ end trace 525608b0ed0e8665 ]--- > [ 32.859722] RIP: 0010:drm_mode_hsync+0x1e/0x40 > [ 32.860287] Code: 31 c0 c3 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 8b 87 d8 00 00 00 85 c0 75 22 8b 4f 68 85 c9 78 1b 69 47 58 e8 03 00 00 99 f9 b9 d3 4d 62 10 05 f4 01 00 00 f7 e1 89 d0 c1 e8 06 f3 c3 66 > [ 32.862680] RSP: 0000:ffffc900000ebb90 EFLAGS: 00010206 > [ 32.863309] RAX: 0000000000000000 RBX: ffff88001c67c8a0 RCX: 0000000000000000 > [ 32.864182] RDX: 0000000000000000 RSI: ffff88001c67c000 RDI: ffff88001c67c8a0 > [ 32.865206] RBP: ffff88001c7d03a0 R08: ffff88001c67c8a0 R09: ffff88001c7d0330 > [ 32.866359] R10: ffffffff822c3a98 R11: 0000000000000001 R12: ffff88001c67c000 > [ 32.867213] R13: ffff88001c7d0370 R14: ffffffff8207eb78 R15: ffff88001c67c800 > [ 32.868075] FS: 0000000000000000(0000) GS:ffff88001da00000(0000) knlGS:0000000000000000 > [ 32.868983] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 32.869659] CR2: 0000000000000000 CR3: 000000000220a000 CR4: 00000000000006f0 > [ 32.870599] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 32.871598] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 32.872549] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b > > Since drm_mode_hsync() has the logic to check mode->htotal, I just extend it to cover the case htotal==0. Signed-off-by: Tina Zhang Cc: Adam Jackson Cc: Dave Airlie Cc: Daniel Vetter [danvet: Add additional explanations + cc: stable.] Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/1548228539-3061-1-git-send-email-tina.zhang@intel.com Signed-off-by: Ben Hutchings --- drivers/gpu/drm/drm_modes.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/gpu/drm/drm_modes.c +++ b/drivers/gpu/drm/drm_modes.c @@ -682,7 +682,7 @@ int drm_mode_hsync(const struct drm_disp if (mode->hsync) return mode->hsync; - if (mode->htotal < 0) + if (mode->htotal <= 0) return 0; calc_val = (mode->clock * 1000) / mode->htotal; /* hsync in Hz */