Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752958AbcKZSCO (ORCPT ); Sat, 26 Nov 2016 13:02:14 -0500 Received: from mail-io0-f196.google.com ([209.85.223.196]:36209 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752653AbcKZSCJ (ORCPT ); Sat, 26 Nov 2016 13:02:09 -0500 MIME-Version: 1.0 In-Reply-To: References:

From: David Herrmann Date: Sat, 26 Nov 2016 19:02:08 +0100 Message-ID: Subject: Re: drm: GPF in drm_getcap To: Dmitry Vyukov Cc: syzkaller , Daniel Vetter , David Airlie , "dri-devel@lists.freedesktop.org" , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3980 Lines: 98 Hi On Sat, Nov 26, 2016 at 6:50 PM, Dmitry Vyukov wrote: > On Sat, Nov 26, 2016 at 6:35 PM, David Herrmann wrote: >> Hi >> >> On Sat, Nov 26, 2016 at 6:17 PM, Dmitry Vyukov wrote: >>> On Fri, Sep 9, 2016 at 1:56 PM, Dmitry Vyukov wrote: >>>> Hello, >>>> >>>> The following program triggers GPF in drm_getcap: >>>> >>>> // autogenerated by syzkaller (http://github.com/google/syzkaller) >>>> #include >>>> #include >>>> #include >>>> #include >>>> #include >>>> #include >>>> #include >>>> #include >>>> >>>> int main() >>>> { >>>> int fd = open("/dev/dri/card0", O_RDONLY); >>>> uint64_t data[2] = {0x11, 0x80}; >>>> ioctl(fd, 0xc010640cul /*DRM_IOCTL_GET_CAP*/, data); >>>> return 0; >>>> } >>>> >>>> >>>> general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN >>>> Modules linked in: >>>> CPU: 1 PID: 5745 Comm: syz-executor Not tainted 4.8.0-rc5-next-20160905+ #14 >>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 >>>> task: ffff8800310dc540 task.stack: ffff88003cbc0000 >>>> RIP: 0010:[] [] >>>> drm_getcap+0x34b/0x4f0 drivers/gpu/drm/drm_ioctl.c:260 >>>> RSP: 0018:ffff88003cbc7c28 EFLAGS: 00010202 >>>> RAX: 0000000000000058 RBX: ffff88003cbc7cf8 RCX: ffffc90001db0000 >>>> RDX: 000000000000005d RSI: ffff88003cbc7cf8 RDI: 00000000000002c0 >>>> RBP: ffff88003cbc7c50 R08: ffffed0007978fa1 R09: ffffed0007978fa0 >>>> R10: ffff88003cbc7d07 R11: ffffed0007978fa1 R12: fffffffffffffff0 >>>> R13: dffffc0000000000 R14: ffff88003bcc6850 R15: fffffffffffffff2 >>>> FS: 00007fcbf4e03700(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000 >>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>> CR2: 00000000006dce00 CR3: 0000000066135000 CR4: 00000000000006e0 >>>> DR0: 000000000000001e DR1: 000000000000001e DR2: 0000000000000000 >>>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 >>>> Stack: >>>> ffff88003c26db00 ffff88003cbc7cf8 ffffffff875a3000 ffffffff88cf0ee0 >>>> fffffffffffffff2 ffff88003cbc7dc0 ffffffff834cb57c 000000000000e200 >>>> 1ffff10000000001 ffffffff875a1ba0 ffffffff882ae930 0000000000000010 >>>> Call Trace: >>>> [] drm_ioctl+0x54c/0xaf0 drivers/gpu/drm/drm_ioctl.c:728 >>>> [< inline >] vfs_ioctl fs/ioctl.c:43 >>>> [] do_vfs_ioctl+0x18c/0x1080 fs/ioctl.c:675 >>>> [< inline >] SYSC_ioctl fs/ioctl.c:690 >>>> [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:681 >>>> [] entry_SYSCALL_64_fastpath+0x23/0xc1 >>>> Code: 3c 28 00 0f 85 88 01 00 00 49 8b 44 24 10 49 39 c6 4c 8d 60 f0 >>>> 74 82 e8 64 19 10 fe 49 8d bc 24 d0 02 00 00 48 89 f8 48 c1 e8 03 <42> >>>> 80 3c 28 00 0f 85 6f 01 00 00 4d 8b bc 24 d0 02 00 00 49 8d >>>> RIP [] drm_getcap+0x34b/0x4f0 drivers/gpu/drm/drm_ioctl.c:260 >>>> RSP >>>> ---[ end trace c6e1afa8cd73b880 ]--- >>>> >>>> >>>> On commit 4affa544adb8077403893e62b9e327fcf87de6f7 (Sep 8) of linux-next. >>> >>> ping >>> >>> Still happens on 16ae16c6e5616c084168740990fc508bda6655d4 (Nov 24). >> >> I suspect this is because we run drm_for_each_crtc() in >> drm_getcap(DRM_PAGE_FLIP_TARGET) on a legacy driver (meaning >> mode_config is not initialized). @danvet, how about always >> initializing mode_config to 0/empty/dummy? >> >> Dmitry, what driver do you run this on? And is CONFIG_DRM_LEGACY enabled? > > > CONFIG_DRM_LEGACY is enabled. > > How can I understand what driver is used? > This happens inside of qemu. This is the device: > crw-rw---T 1 root video 226, 0 Nov 26 17:45 /dev/dri/card0 Usually by looking into `dmesg` and grepping for 'card0', or by inspecting: /sys/class/drm/card0/device/ or more importantly looking at the symlink: /sys/class/drm/card0/device/driver Thanks David